Increasing Power On Motorcycles

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To simplify this article let's focus on the Harley-Davidson V-Twin engines, but you can apply the information below for all 4-cycle air-cooled engines.   One word of advice.  If you want more power buy a bigger stock motorcycle (see Question #9 and #14).  To spend a fortune on building a larger engine is a losing game.  You will always lose reliability and your money.


Most cruiser riders who buy a new motorcycle just require an enhanced exhaust sound volume to enhance the riding experience and for safety reasons to be heard when in traffic.  To obtain the sound, you need to buy pipes.  My advice is to listen to pipes on existing bikes first before you buy because a nice looking pipe system may be a lousy sounding pipe or a poor design can be a painful experience.  Example: swept pipes facing the pavement can send a secondary sound pulse reflection right back at your head and it will not sound nice.  Or the pipes may have resonance sound problems where a high frequency tone is sent toward your head that will fill your head with noise causing ringing in the ears.   Many riders that wear ear plugs do not realize they have a resonance problem due to wide-band frequency sound emissions that are offensive to the body creating vibrations to develop in the skull and ear bones.  Properly designed pipes will not have these resonance problems and you can ride without earplugs.  Yes, even OEM factory offered racing pipes may have awful resonance emissions.

Before you buy pipes consider slip-on pipes. They function just as well as full system pipes and cost a lot less and are easier to install.  Consider when you buy the pipes which fuel management system you can buy that will work with your pipes.  You can install louder exhaust pipes without installing a fuel management system as long as your motorcycle has oxygen sensors in the exhaust pipe headers.  A four wire sensor is far better than a two wire sensor, but don't be surprised your bike only has a two wire oxygen sensor.  If so, it means more modifications can not be made, like adding a high-flow air cleaner along with your pipes as the 2-wire oxygen sensor can only make adjustments to the fuel management computer in a small range.  This is why you see aftermarket 4-wire oxygen sensors being sold with some pipes as they can handle a much wider range.

Okay, now you have installed a high-flowing air cleaner, louder pipes and a fuel management system.  This is a "safe & sane" method of generating more power and a cooler running engine.  This modification will not damage pistons, rods, crankshaft, valves, lifters, etc.  You only get 5-10 horsepower increase, but it is enough for most of us.


The next step requires engine tear down high performance components.  Mild street cams, lifters, adjustable push rods, large bore pistons (not requiring case boring), ported cylinder head with larger intake and exhaust valves with a more advanced fuel management system in some cases.


This is an engine build between the Stage 2 and Stage 3.  I consider the stock 110 c.i. and the 120 c.i. Harley-Davidson Screaming Eagle engines in this category as they are big motors with street manners.


You will need the stage one kit with more powerful coils and lower resistance spark plug wires, electronic ignition to adjust spark advance curve, huge pistons that do require case boring, stroked crankshaft with stronger connecting rods along with better flowing heads and high-duration cams, stronger lifters and push rods.  Compression ratio is also increased.  A new belt driven primary system is required to handle the extra power.  Higher compression and larger fuel injectors to flow more fuel will be needed too.  It may even be using Nitrous Oxide for momentary power boosting or high octane racing fuel.  A more powerful clutch is needed.  The power is awesome, but reliability is going to suffer.  This is a mild racing engine, not really a street engine.  It will run really hot and the wear and tear on the internal engine parts will be accelerated vastly.  Believe it or not there are many Harley-Davidson Twin-Cam engines with these modifications.  Do they work?  Yes, but reliability is going to suffer.  The prime culprit is overpowering engine and driveline components that cause breakage and excessive heat that overcomes the oil's ability to lubricate parts.  Galling of pistons, heat cracking valves and scored shafts, broken rods, crankshafts twisted, etc.  Harley-Davidson does sell Screaming Eagle high performance engine parts, but you need to be aware these are racing components, not for street use.  The fact riders use these hyped-up motors on the street will one day discover they have a broken engine that will be near impossible to fix and expensive to repair.  Reliability suffers.


This is a full-blown gasoline or gas/nitrous oxide or alcohol race engine with a blower or turbo-charger with beefed up engine components much larger then the Stage 3.  The engine size will be humongous.  It will run so hot you can't ride it on the street.  Racing only.  Harley-Davidson makes a street version 103 cubic inche Stage 4 stroker engine kit for the Twin-Cam engine.  Keep in touch with Harley-Davidson as they are doing some amazing feats beefing up their engines surpassing 113 cubic inches and going higher as I write this article.


This set up is a nitro methane top-fuel engine.  Generally only used on a drag strip.  The drive chain will be massive in size with triple-width links.  Racing only.



1.  Question: I am concerned of E15 fuel being introduced in my stock engine.  I now am even more concerned of overheating my planned new high-performance engine I want to build.  Should I hold off for now?

Answer:  A stock Harley-Davidson already runs lean and runs hot due to boring and stroking at the factory above 88c.i. and it is causing problems even with pure gasoline and more so with E10 (10% ethanol) in the 96, 103 and 110c.i. engines.  If E15 is pushed on us a lot of people are going to see severe engine damage.  Mostly scuffed pistons and cracked valves and burned valve seats and maybe cracked cylinder heads.  If detonation becomes an issue watch out!  The damage will be broken pistons and rods that will destroy the entire engine.  Fortunately on a Harley these are easy to fix, but still an expense.  You will need to purchase a fuel additive that will counter the hotter fuel's damaging effects and hopefully purchase a better oil formulated to help stop heat-related galling of valve stems and pistons.  I would start using Marvel Mystery Oil in the gas in your bike as it will prevent such disasters due to lack of lubrication.  I would not hop-up a street engine at this time.

2.  Question: I have one of those hot running 110c.i. stock Harley's.  What can I do to cool that engine off?

Answer: A stage 1 tune up will cool the engine down a bit as it will not run as lean.  A larger oil pan that holds more oil will help as a finned oil cooler.  Some oil coolers are now coming with forced air cooling fans like Jagg.  Other than this there is not much more you can do.  The engine bore is so large it is creating a huge amount of explosive heat in the cylinders.  The cooling fins are doing their job, to shed heat as a heat-sink away from the cylinders into the ambient air and that heat is between your legs.  Even if you were to find a personal comfort solution the engine will still be overheating constantly.  The rear cylinder on the Harley does not get cool air, it only receives boiling hot air from the forward #1 cylinder and that is one cause for #2 cylinder failure when the piston and valves overheat and this affects all Harley-Davidson V-Twins especially more so the Big-Twins.  The Sportster Evolution engines do not burn up like their bigger brothers do.  Ultimately, a smaller engine can be a solution.  The biggest, baddest, torq-pork engine is becoming a nightmare for many.    

3.  Question:  I am thinking of buying a Harley with a 96c.i. engine.  Will I have trouble with it?

Answer: You will.  Read the article: What You Need To Know Before You Buy A Harley-Davidson Motorcycle but if you are thinking you will have a heat issue that will damage your bike you will be okay with the 96c.i. stock engine with a Stage 1 tune up unless E15 fuel is used.

4.  Question: I want to install larger pistons in my bike.  Must I rebalance my crankshaft?

Answer:  If you buy pistons that are not matched specifically for your engine you run the risk of buying pistons that if installed will require you to balance your crankshaft.  Check with the piston manufacturer to get the pistons that do not require rebalancing the crankshaft.

5.  Question: Why do riders want more and more power?

Answer: Human nature?  After owning over 20 motorcycles I have finally settled down to lower power engine.  You can have a powerful engine, but what good is it if it keeps breaking down, costs too much to run.  Bragging rights?  Nobody cares.  What does it profit a man for others to gawk at your bike?  You can't impress anybody and there is always somebody else who trumps you anyway.  The power thing can be very addictive and destructive to your wealth.  It can be a healthy phase in your life to do it at least once.  It is fun to build an engine.  Whatever makes you happy makes you happy, but just make sure it makes you happy.  Powerful engines breakdown and fail right when you don't want it to happen.  There was a time not so long ago when a stock engine would be deemed the most reliable to purchase, but Harley-Davidson is breaking that rule making its stock bikes larger and hotter.

 6.  Question: I have the Stage 1 kit.  What can I do to gain more power without engine work?

Answer: Add low resistance spark plug wires, install Iridium spark plugs.  That will give you a strong peppy throttle response you can feel.  Later you can add higher voltage ignition coils.  Fuel additives can give you a bit more power too.  Use Synthetic oil to reduce engine friction.

7.  Question: Piston ring mfg says to use a 0.005" ring gap, but the piston mfg says to use a 0.008 ring gap.  Which one do I use?

Answer: The piston manufacture has the final say.

8.  Question: At what point must I consider installing a stronger primary and drive chain/belt on my Harley Twin-Cam engine? 

Answer: Anything over 96c.i. you should go with at least a stronger drive belt S&S Cycles makes a X3N carbon cord drive belt that is vastly stronger than stock belts.  The stock primary chain is very strong and should hold up just fine, but with an engine over 110c.i. a belt drive primary system should be installed to handle the elevated power/torque.  The clutch plates should also be stronger for anything larger than 96c.i.

9.  Question: What can I expect when modifying my engine in regards to reliability feasibility?

Answer: If you stay with pistons that require no case boring to fit the cylinders you will generally be staying within the safety factor of the crankshaft and connecting rods, even with hotter street cams installed.  When you bore the cases to install larger diameter pistons you then need to install stronger connecting rods and even a stronger stroked crankshaft flywheel assembly and case bearings.  Reliability is going to suffer and it is not unusual to see cracked cases.  The money you will spend hopping up your stock Harley engine to large horsepower can be a losing game as all the other items that needs to handle that power to the rear wheel will wear out quickly or break.  It is worth your consideration to buy a complete engine designed to handle the power rather than try to increase power in a stock engine.  Buy a brand new big bore engine and reliability will increase.  It won't be cheap, but it is really the only best way to get big power.  It's like a young man who has a small bike.  Instead of wasting money powering up a small bike it is way better buying a bigger motorcycle to get more power.  When all is said and done, it is never a good idea to hop up a stock motor.  You change all the design elements out of parameters and reliability is going to cause engine and drive train failure.  You see it in the magazines and custom bike builders but it is not a smart thing to do. Stage 1 modification is as good and even better than stock.  Stage 2 expect reliability in regards to accelerated wear and tear to be greatly diminished from stock and Stage 1. Stage 3 is a failure waiting to happen and a Stage 4 racing engine is flat out going to fail in a very big way.  If you install a completely new engine, even though it is big bore, reliability returns to Stage 1 or Stage 2 depending on size as heat generated is the culprit to early engine failure.  But a new big bore engine will overstress the primary, transmission and drive line components if those elements are not upgraded to handle the power.  Big bore engines are not touring bikes they are rally and bar-hoppers and drag racing beasts.  Stage 1 tune-up is the best for reliability and recommended for touring, longevity, resale value and fuel mileage.  Big bore stock modified engines will decrease the value of your motorcycle.  The value increases only if you buy a new big bore engine, to a point.  People are afraid of large engines as they just cause trouble.

10.  Question: Can I purchase a used fuel management computer for my bike?

Answer: Only if the fuel manager is compatible to your specific model and year and brand of bike.  You will see more and more used fuel management modules for sale simply because Harley-Davidson has changed the wiring and sensors on their bikes from the old J1850 data bus to the new CAN bus system.  So the old Power Commanders, Thunder Max, FuelPaks and so on are not longer compatible with the new CAN bus wiring.

11.  Question: What is your opinion on the Harley-Davidson 120 engine?

Answer: Bad news.  While the engine has upgraded components to handle the stress and strain of the increased horsepower it is still weak in a critical area and that is the crank cases are actually off the shelf stock cases bored out to accept the 4.060" pistons.  The connecting rods are stronger, but they are still of the I-beam construction.  They may work, but H-beam is stronger for this displacement motor.  Even the cylinders are stock with the same cooling fin depth so heat is going to be horrific and unmanageable.   The engine is going to work, but for how long?  And you need to be reminded this is a work-in-progress "race engine" only so Harley-Davidson will sell you one, but the warranty is going to be nil for street use.  It means the engine is going to cook itself to death despite an oil cooler.  When Harley-Davidson offers this 4-5/8" stroked 120 engine in their street bikes only then can you consider a certain degree of reliability will be inherited.  However, Harley-Davidson has been known to sell defective and poorly designed engines that self-destruct and are unreliable (think Twin-Cam engine).  There are bigger and stronger engines out there with better warrantees; RevTec, S&S, TP, Zipper, Jim's, etc.  Jim's has a big 135 c.i. race engine that bolts right into a Dyna or Touring frame and is sold by Harley-Davidson.

12.  Question: What about the Harley-Davidson Remanufactured Engine Program?

Answer: If you don't mind being stuck paying Harley-Davidson's dealers to remove and install your new engine then it is a very good deal because you do obtain a good warrantee and you know the install will be performed properly and the turn-around time is quick.  Other motorcycle brands don't even offer you such service.  And H-D will also hop-up your engine using their Screaming Eagle engine components for more power.  No other brand offers such factory service.  I think it is a great program. 

13.  Question: How do I know what upgraded components I need to gain horsepower?

Answer: Most riders do not know what they are getting themselves into when they increase power in their stock engines.  Generally, it is a total disaster to alter a stock engine beyond a Stage 1 setup.  Why?  Because when you go to Stage 2 or 3 so much power is increased the engine cases, bearings, shafts, everything are now working overtime beyond the engine's design.  The safety factor has been grossly reduced from a factor of 5 to 2 and parts breakage and greatly accelerated wear and tear is produced reducing engine longevity.  For example:  The Stage 2 and Stage 3 Harley-Davidson Screaming Eagle piston, crank, head and cam kits will absolutely ruin your engine.  Yes, it will work for some time, but those pistons will burn in their bores due to the horrific heat.  Bearings and shafts will flex and strain and eventually let go without warning.  Read the fine print!  The kit is a racing engine not a street engine.  The warranty will also have lots of fine print escape clauses too that will harm you.  The better way is to buy a new engine already designed for the larger displacement and power increase.  But don't forget you must also beef up the transmission, clutch, primary system and final drive belt and pulley.  This includes strong bearings on each component.  You may also discover the engine and transmission cases will crack even with larger bearings installed and expensive crank and transmission shaft splines will strip!  So, by buying a piston, barrel, heads, stroked crank, H-beam rods and cams kit will give you power, it will destroy your engine much sooner than a stock engine.  All of your invested money will go up in smoke.  It is a total waste of money.  Plus, it ruins your resale value of the bike.

14.  Question: What about those new Harley-Davidson's with bored out engines?

Answer: If you want a fast Harley-Davidson that is the intelligent way to proceed.  Buy a stock Harley already powered by a large cubic inch engine.  The entire bike is under warranty.  If something goes wrong the part is covered (or should be) under warranty so it cost you nothing.  But even then, there are a lot of rider complaints of excessive heat generated by the 110 c.i. engine and larger size engine will only get worse.  There is no doubt in my mind if you ride a 88 or 96 c.i. engine you will see longer engine life than the new bigger size twins.  Heat is the enemy of all engines.  More power means more heat and that means more stress, strain, wear and tear.  So the expensive new, yet stock Harley-Davidson motorcycle you bought with a 110 c.i. engine (or larger size) is a better deal than hopping-up your smaller stock engine to create more power, but the larger 110+ stock engine is still going to cook itself to death as it can not shed the heat it creates away from internal reciprocating parts.  And that's the problem.  You can't see the damage being made until you discover the engine has prematurely worn out parts needing replacement.  Consider the H-D 110 c.i. engine a Stage 2.5 engine as it has a stroke crankshaft, big pistons, ported heads,  large fuel injector, but it still has mild street cams.  Install wild race cams in it and it will jump to a Stage 3.

15.  Question: How do I know when it is time for new top end overhaul?

Answer: Usually, the first sign is when you see oil dripping out of the stock air cleaner element or out of the breather pipe.  As piston and piston rings wear combustion blow-by slips past the rings and cylinder and increases crankcase pressures.  The higher pressure forces a small portion of the oil that is normally scavenged back to the oil pump is blown in a mist form out the breather.  When you see blue smoke from the exhaust pipe it means valve stem seals are leaking, pistons are worn or both.  It is time to overhaul the top-end.  This time will come upon you frequently if you have a Stage 2 or Stage 3 engine.

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16.  Question: When should ported cylinder heads be used?

Answer: Only when larger pistons have been installed.  You need more air flow.  Let's say you have a 88 c.i. engine and you go with a 96 c.i. piston kit you don't have to port the heads as you can and should install longer duration cams that will flow air real good.  But if you go larger you must install heads with larger valves and ports so the engine can breathe.  If you have a stock 96 c.i. engine you can go up to 110 c.i. with the stock heads as long as you install the cams too as previously mentioned. 

 17.  Question: Can I expect better performance with ported heads on a stock engine?

Answer:  Yes and no.  Yes, if you just match the port opening of the intake manifold to the cylinder head for a smooth transmission of air flow into the engine.  Don't forget to grind down any gasket material that may obstruct flow.  Do this also with the exhaust pipe, exhaust pipe gasket.  You will get more power just doing this.  But if you install a machined ported (polished ports or not) on a stock bike you won't see a power increase.  You may even see a power decrease as larger ports can decrease air velocity slowing down fuel mixtures getting into the cylinder and can even slow down the exhaust flow creating back-pressure on the pistons and that will certainly slow you down and ruin gas mileage.

18.  Question: My Stage 2 engine is running rough and hard to start.  Sometimes I can feel the starter straining to turn over the motor.  What could cause this?

Answer: The first thing you need do is get a can of fuel injection cleaner and pour it in the gas tank and ride the bike hard up a long hill with the engine hot.  I believe compression has risen in your engine with an accumulation of carbon layers on the piston crown, head and valve surfaces.  This will mess up your ignition timing and make for hard starting and rough running.  Gasoline should have these additives already so maybe you are getting some cheap gas somewhere.  When you buy gas you should consider buying your fuel from a trustworthy vendor.  There are many foreigners who do not speak English buying, owning and running gas stations whom I will never trust.  When bad gas is found it is often with these independent gas stations.  Find a large American regional Corporation who manages national brand name gas stations like; Shell, Texaco, Chevron, Exxon, etc.  You will receive better quality fuel and you will know where your money is going.  Do you really know if those independent gas station owners are sending money to terrorists to buy bombs and bullets to kill our people and allies?  Think twice where you buy your fuel from.  Keep using fuel additives at least monthly.

19.  Question: Have you heard of compensator failure?

Answer: It is not expected to fail in a stock or Stage 1 engine, but a Stage 2 and above is advisable to upgrade to the Screaming Eagle compensator.  The compensator sprocket has stronger springs with increased travel and is seven times stronger than the stock compensator.  People who have multiple stock or the upgraded SE compensator failures are usually a victim of a mechanic who did not properly torque the compensator nut twice, torque, loosen, then final torque.  If they torque it only once the nut can back off and all hell breaks loose in the primary case.  It would be nice to wire the flange screw so it can not back off from vibration.  Follow the instructions given by Harley-Davidson on how to install the compensator.

20.  Question: My new stock Harley vibrates.  What is causing it?

Answer: Dealers will tell you, "Harley's vibrate.  Get used to it."  It is true.  That 45 degree crankshaft is the culprit.  Only Harley-Davidson dares to manufacture an engine with this configuration and I mean "only".  If your bike is vibrating more than normal it can be a simple as a loose or cracked motor mount, bad gasoline or worse a crank shaft that has become unbalanced.  Other things can create vibration, but there are a lot of riders out there who have out of balance crankshafts.  Harley-Davidson does not weld the crank webs to the crank pin and they should and that will solve this problem.  I had one go out on me and the vibration became so bad it was hard to hold on to the handlebars and the foot pegs and seat was not fun.  Aftermarket cranks are often welded and even balanced way better than a stock Harley crank.  The problem with Harley-Davidson dealers is they will not weld the crankshaft so if you have them replace the crank it can slip again.  It is my opinion this is an ongoing defect.  Sure, most cranks do not slip out of alignment, but those that do make for angry customers.  And the way some riders ride they throw their crankshafts out with stock engines.  If you increase power on your engine the crankshaft can slip out of balance at any moment at any time.  It is expensive to fix as the cases must be split and a new crankshaft installed.  Dealers will not balance it for you, they just put in a new crankshaft.  Motorcycle magazines often list ads of machine shops that do crankshaft balancing and crank web and crank pin welding.   

21.  Question: Must I install a billet cam plate?

Answer: If you have a 1999 to 2006 Twin-Cam engine you should totally upgrade the cam chain tensioners and oil pump along with the billet cam plate.  Harley-Davidson has an upgrade kit.  It will convert your engine to the newer hydraulic cam chain tensioners system, which is not perfect, but is way better than what you have now for it will last longer before the chain tensioners shoes need replacing.  Still, you must replace those worn out cam chain shoes even on the hydraulic system.  The other option is to install gear drives to get rid of the cam chains and install a Fueling brand oil pump upgrade.  The cam drive system in the Twin-Cam engine is a nightmare contraption.  It should be totally scrapped by H-D and a gear system like the Sportster Evolution engine has and these cam drive problems will be fixed for good.  See Question #22 below.  The upgrade kit also upgrades the oil pump scavenging 40% and higher capacity and the outer chain is now a single row chain instead of the multi-link silent chain used on older Twin-Cam engines.

22.  Question: I was told if I purchase a clear cam cover I can see the condition of the cam shoes.  True?

Answer: Yes, but you still can't see the condition of the inner cam shoe as it is buried deeper behind the cam plate.  Luck will have it that the outer tensioner shoe wears out quicker than the inner shoe so you should be okay.  Just remember, when it is time to replace the outer shoe, you must inspect or replace the inner shoe that will not be seen by the eye until you remove the cam plate and cams.  If you keep checking the condition of the outer cam tensioner shoe (like using the Roland Sands clear cam cover) you won't have any serious problems with the stock system.  But you got to know when to replace the shoes, so go take a look at the thickness of some new tensioners shoes so you will know when they are getting a bit too thin for comfort.  When they are worn down, don't delay, replace the shoes.  If you don't?  The engine can grenade itself totally ruining the entire engine.  This is a serious and expensive problem most Harley riders do not understand.  They even believe the new hydraulic system fixes the problem, when it does not.  It only give you more miles before the engine will self-destruct.  Those shoes still must be replaced regularly on all Twin-Cam engines... all of them!  Nobody escapes.  Make sure the shoes are inspected and replaced.  The non-hydraulic system shoes can totally fail at less then 15,000 miles.  The hydraulic system shoes should be inspected each 20,000 miles to be on the safe side.  Rumor has the shoes on the hydraulic system can last 70,000 miles.  Time will tell.

23.  Question: How can I tell if my engine has been upgraded or not?

Answer: Your best bet is to consult Harley-Davidson to see if your engine has been upgraded by the factory when the engine was made or later on by a dealer.  A repair record should be generated.  Buying a used bike you may have to disassemble the engine somewhat to take a look inside.  When in doubt assume your engine has never been upgraded and act accordingly.

24.  Question: I am curious about your point of view regarding pre-Twin Cams engines called Evolution (or Evo) engines that powered older Harley Davidson motorcycles. 

Answer:  First, we must not confuse the Sportster's Evolution engine with the Big V-Twin 82 c.i. Evolution version made in 1984 and discontinued in 2000 and in 2001 the Twin-Cam engine came into production.  The Evolution name is the same, but the engines are not identical by design or of the same size.  The old Big-Twin Evolution engine had a lot of problems with reliability and overheating not to mention the camshaft angle was severe in relation to the rocker arms that actually caused the push rods to snap, valves would be swallowed ruining the engine.  Many bearings in the engine were not strong and the engine cases were also weak and would flex under strain and the bearings would fail again, ruining the engine.  Also, in the days this engine was in production the technology and the metallurgy of metals were weak causing premature wear and failure, but it was a vast improvement in its day.  The engine could be run hard and lasted longer than its predecessors.  For these reasons Harley-Davidson developed the Twin-Cam engine design which solved many of the problems the Big-Twin Evolution engine had, but created a rat's nest of problems in the Twin-Cam engine too.  Slowly, the kinks are being worked out on each engine revision, but I can bet by the time all are worked out it will be too late as the Environmental Protection Agency (EPA) will have mandated the retirement of all air-cooled engines.  The older the Harley-Davidson engine is the worse it gets in regards to longevity and reliability.  But, there are brand new Flathead, Shovel, Knuckle and Panhead engines all made to modern specs with improved components and that is where you will gain the best reliability with the highest horsepower with a retro design.  I would not waste money trying to build horsepower from a stock OEM Harley-Davidson old design engine for it will always be breaking down. 

25.  Question:  I had my engine's power increased but now it is very hard to start and my mechanic says I now need compression release.  He wants to take the heads off and drill releases into the heads.  Is this the cure?

Answer:  Yes, it is the cure, but there is another way.  Install Wimmer's Custom Cycle compression release.  It requires no engine modifications or disassembly and you can do it yourself.  Remove the spark plug, install the compression release device over the spark plug hole, install the new spark plug Wimmer's gives to you for it has a groove in the threads to work with the compression release.  Do the same with the other cylinder and the job is done.  

26.  Question:  My transmission is stock Harley-Davidson.  How much power can it take?

Answer:  Good question.  Nobody likely has a strict formula for a solution that I know but I have a good bit of advice.  Under 100 horsepower your stock transmission is fine.  Over this go with a Baker 6 speed transmission for it will handle everything you can throw at it.  If you do not know the horsepower then use this advice; up to 114 cubic inch your stock transmission is fine.  Anything larger go with a stronger transmission.  My advice is generalized, but is on the safe side.  I assume there is no turbo or blower or nitrous oxide being used otherwise you got to go with the Baker transmission right away.  Also, the Baker transmission has better placement of shaft bearings so they do not bend or flex like stock transmissions do.    

27.  Question:  Should I upgrade the ignition coil?

Answer: You may need to upgrade the coils and the ignition timing module if you bore and/or stroke your engine to a larger displacement and/or compression ratio.  If you just added a Stage 1 kit, don't bother.

28.  Question:  Do all Harley-Davidson's have shaft flexing problems?

Answer: All big twins except the Sportster engines.  The Sportster engine  is a "perfected" engine with no engine or transmission defects.  It is the engine Harley-Davidson should just cast into a larger mold to "replace" the Twin-Cam engine and stop all the unreliability nonsense.  The Twin-Cam engine is a hopeless pile of junk that will not last due to so many faulty designs in that engine and transmission.  Read article:  What You Need To Know Before You Buy A Harley-Davidson Motorcycle Now some readers may disagree for they have been "lucky" but I assure you the defects are real and if you visit any motorcycle repair shop you will see for yourself just how busy those shops are fixing these failures.  Your turn is coming, I promise you.  If you add more engine power to your bike those crankshaft and transmission shafts will flex, crack and break the shafts or the bearings and cases.  This is why Harley-Davidson "beefed up" its engine cases and bearings for the 110c.i. and larger engines, but the flexing still happens.  It can't be stopped for the shafts are too long.  If you look at the Sportster engine primary it does not extend as far out as the Twin-Cam does and the transmission is reversed like in the Baker system where the drive output pulley is on the right side.  This creates shorter shafts and the shaft flexing and bending is no longer an issue.  Read this article: Harley-Davidson Sportster 1200 & Why You Should Buy One

29.  Question:  Can I purchase an extended warranty plan?

Answer: On a stock Harley-Davidson by all means yes, do so, if you plan to keep the bike and not trade it in when the original warranty expires.  But you got to realize that if you do purchase an extended warrantee the moment you hop-up the engine in power that warrantee is null, void and worthless.  No matter what some salesperson tells you, he/she is not authorized and has no authority to enforce or deny a written warranty.  If the written warranty says it is void, believe me, it is void.  That is why when you or your mechanic purchases Screaming Eagle parts there is a warning that the warranty may be voided.  The bottom line is you can't purchase a extended warranty on a hopped-up motor, only a stock bike.  I will give you some advice.  Don't follow the herd.  The crowd mentality is always wrong (as Las Vegas, Reno, Wall Street, real estate markets has proven consistently).  If you want more power just go buy a brand new stock Harley-Davidson with a factory extended warranty and leave the bike alone.  A Stage-1 kit can void a warranty, but most likely will not especially if a H-D dealer did the fuel tuning job.

30.  Question:  What exhaust pipe can I buy that does not require a fuel management tuning?

Answer: Supertrapp makes pipes that have resister plates that are easily removed or added so you can tune the stock engine's air and exhaust flow through the engine without bothering with tuning up the fuel mixture.  Other manufactures are now doing the same to reduce noise emissions that gives the same results; no fuel programming required.  I bought Supertrapp for my stock Sportster 1200 and they sound good and put out strong power.  With a K&N air filter and Supertrapp 2-into1 pipes with 10 disks (8 is stock) it's like igniting a rocket to the back of the bike they way it insanely accelerates.  I did not need to retune the fuel system.  Beware of companies that sell quiet baffles for their otherwise loud pipes.  I tried Vance & Hines quiet baffles and it was a rotten joke on me!  They were still horribly loud and obnoxious and I had serious mixture problems with their fuel management computer.  I also found them to be "unresponsive" to solve the problem and refund my money.  I do not recommend their products anymore to anyone, not with such poor customer service and treatment.  I even wrote a letter to the President and it was ignored.  Supertrapp has "infinite" control so you can "fine tune" your exhaust with the disk system they use and you don't have to take apart the pipes or remove them from the bike to make these changes.  This saves you time, grief and gives you the sound and performance you desire for street or for race use.  And, the pipes are "stainless steel" so they don't corrode and rust out like other brands.  And, the price is actually low for what you get.  My pipes were only $500 with no need for a fuel management computer.  Very nice.  One more thing: They are Made in the USA. Read this article:  Motorcycle Exhaust Pipes and Dyno Tuning

30.  Question:  I plan a Stage-1 on my bike.  Will it void my new warranty?

Answer: It can, depending on what item fails.  If a transmission or drive component fails it should not, but if a piston or valve burns that can void the warranty if they find the fuel mixture was too hot (lean) or detonation was taking place that caused the failure.  Even installing H-D Screaming Eagle components by a Harley dealer will void the warranty.  Read the fine print!  

31.  Question:  What fuel management device should I use to tune my bike?

Answer: There are many products sold today, but ThunderMax EFI Module with Auto Tune ( ncezi is standing out from other products for a few reasons.  You just install the device, set it up and away you go.  Then, when you sell the bike?  You can take the ThunderMax with you and use it to tune your new bike.  That is a strong selling feature so you do not have to keep buying EFI devices when you buy a new bike.  The device is not an add-on computer... it completely replaces the original factory EFI and that is another strong benefit for it does not complicate troubleshooting or void or burn up the factory EFI, think about that.   Cobra Fi2000 PowrPro is a nice product that is easy to install, plug 'n play ease and cost less than the ThunderMax and it will adjust for any future engine alterations without reprogramming.

32.  Question:  I need a economical power increase.  What do you suggest?

Answer: There is one kit available I think is worth consideration for what you get is quite amazing.  AMS MotoMachine has a big Harley-Davidson V-Twin kit starting at just $1,495.  You get CNC ported heads (without valves installed ?), cylinders, pistons, rings, even a cam gear drive conversion with cams, pushrods and gaskets.  That's a lot of stuff and it is bored out too for street-level high performance.  Check them out.  Just shop around to find the best deal.

33.  Question:  How do I determine throttle body size?

Answer: Go to Dan Vance Racing as they can better make a proper choice for you.  Generally speaking on a 103 to 110 all the way up to 124ci size engine you can use a 55mm or a 58mm throttle body for street use.  A 62mm to 70mm are huge, requires larger injectors, but the engine will lose street politeness as there is too much power going to the rear wheel and better off for racing purposes.

 34.  Question:  What is a 3-step torque procedure?

Answer: This is used, for example, on the H-D compensator nut inside the primary case.  You first torque the nut to 100'lbs, then you loosen the nut one full turn, then finally torque it down snug at 140 foot-pounds.

35.  Question:  I need parts for my Sportster.

Answer: Try: Sporty Specialties  For machine shop try: Dutchman Racing


36.  Question:  What about oil?  I see so many companies advertising their oil for Harley-Davidson.  Who's oil is best?

Answer: The good news is Harley's oil is best.  Best being it is not bad for you and it can be trusted especially the synthetic oil is the best for you to use in your bike.  Now, there are some minor exceptions.  What if you have a noisy transmission?  Well, it would be good to try an aftermarket brand of oil that is thicker (high viscosity) and this will smooth out the shifting and reduce noise.  Other than this, synthetic H-D oil is good stuff.  It is also good to support the motor company by buying their oil.  Can you use other brands of motorcycle oil in your Harley?  Yes, you can, as long as the oil is designed for V-Twin engine, transmission and primary chain case you can use it.  The oil will likely say compatible with Harley-Davidson.

37.  Question:  What is your take on permanent wheel balancers?

Answer: These devices permanently attach to the motorcycle wheel hub and keep the wheel balanced using a fluid or solid medium.  They can be good for those who seem to need them due to a design flaw that creates wheel balance problems, but for most of us riders they are not needed.  It won't hurt to install them, but I have not done so.  I have read some riders experience problems with the devices.  I say you don't need permanent wheel balancers, but if you want them who am I to say otherwise?  If they work for you, then be happy.  In my book  "Learn to Install New Tires on Your Motorcycle and Fix Flat Tires" I explain wheel balance and how most cruiser riders are riding bikes with unbalanced wheels and do not even realize it with no adverse effects.  Example: do you have missing wheel weights on your wheels?  You likely do and never knew the wiser.  However, in the book, I do show you how to balance your wheels.  It is easy to do. 

38.  Question:  I plan to purchase custom wheels for my bike.  Should I also purchase a custom wheel pulley?

Answer: Only if you want the looks.  It is not wise to pay money for expensive objects that wear out, and pulley's do wear out.  However, you can have the pulley renewed with a special process that coats the teeth with a new set.

39.  Question:  I installed all 18 baffles in my Supertrapp exhaust and the sound still sounds muffled.  I want to hear a more crisp pop in the note.  What can be done?

Answer: I agree the baffles are stacked too close together that is great for fine tuning, but the classic Harley sound suffers.  To get the sound more thunderous, yet crisp to hear each cylinder fire like using a Thunderheader pipe you can insert three #8 flat washers between one set of plates, skip three plates and do the same again.  That is all you may need.  This opens up the gaps between the plates to allow the sound to escape and increases exhaust flow too.  You can purchase a open cone, but the pipe can become awfully loud as the pipe muffler is a megaphone design amplifying sound.  If you have a Cobra Fi-2000 Powr Pro fuel manager it will automatically retune the engine for you.  The only problem I do not like about the Supertrapp baffle system is the bolts/screws that hold the baffles into the pipe expose the screw hole and the screw threads itself to exhaust which places crusty carbon on the threads.  When you try to remove the screws you have to loosen/tighten/loosen/tighten to get them out and even then some screws will snap in two.  Just too much carbon build up. This will happen even with copper or aluminum anti-seize compound on the threads.  You then have to drill and tap new threads.  Not all the thread bolt holes have stripped, just a few will over time.  

40.  Question:  I have installed pipes, air cleaner and injector tuning on my Victory motorcycle, but I want more power.  Can I install cams?

Chasing horsepower is often a losing experience unless you bore those cylinders out because that is where the power really is hiding, then cams, head porting, larger injectors, etc follow to complement the larger cylinder bore.  I would try to remove the baffles in your current Stage 1 pipes and see what develops.  If you feel the power increase, then you know the Victory pipes are restricting gas flow in and out of the engine.  It's an easy test to do and you don't need a dyno, just feel the pulling power.

Problem with Victory engines is they are too smooth, so when you increase power, you don't feel it like a Harley would.  I hated that dull feeling I had with my Kingpin Victory, so I got rid of it and went back to Harley (Sportster XL Custom).  I keep it as a Stage 1 and leave it at that.  If you want more power?  Why bother with all the grief you are experiencing?  Just trade it in for a newer bike with a larger engine, maybe the Indian Chief? 

Live and learn, stop chasing horsepower because it only costs you money, money AND more money.  Everybody is stealing your money for a few ponies of power that you'll never be satisfied with.  It is true, it is like an addiction seeking more and more power.  I fell for it most of my life too, but I got out of it and learned to live with just a simple Stage 1 for more exhaust sound and a cooler-running engine. 

You need to come back to reality and learn that chasing power is nothing but grief and often ruins your engine too making it unreliable and not fun to ride anymore, you start to hate the bike because it will not reach your lofty expectations.  I know, I did it too.  My advice is to stop what you are trying to achieve with your Victory.  Maybe get some better-flowing pipes and end it right there.  If you need more power, then go buy a bigger engine bike and just do a Stage 1 and learn to enjoy that outcome.

It's not what you want to hear, but if you think about it, it is good advice for the long term.  Learn to enjoy what you have.

41.  Question: How can I stop spark plug fouling?  I am not burning oil.

Answer: It's likely the tune-up needs modifying, but you can install higher-power ignition coils and replace your original equipment spark plug wires as they do wear out.  Replace the spark plug wires with a spiral-core type cable.  Replace your spark plugs with E-3 brand plugs or try the iridium spark plug which resists fouling.  These plugs and wires will increase the fuel burn giving you better mileage and performance horsepower increase.  The hotter the spark, the more power and economy you will get.

42.  Question: What about tire balancing beads?

Answer: They work, but at low speeds they will make your steering heavy to handle which over time becomes tiring.  In my book, "How to Install Tires on Motorcycles" I talk a lot about tire balancing and why it is not often needed, but is easy to do.  Most riders are riding on unbalanced tires because as the tire wears out it falls out of balance and by the time you change the tire it is way out of balance and you never much noticed the difference.  At high speeds above 80 mph tire balance become an issue but for most city riders tire balance is no big concern.

43.  Question: Should I have a dealership build my high performance engine?

Answer: The best way to do it is to do it yourself, but it means having patience and purchasing the tools and knowhow.  If you are young as I was being 14 years of age when I started overhauling and hopping up motorcycle engines I say go for it.  Yes, you can have a shop or dealership build your engine.  Today, I believe the better bet is to buy a complete big-bore engine and just insert it into your frame, tune it and and ride.  It's a fast turn-around and the engine comes with a warranty and there are many engine brands to pick from.  Subscribe to American Iron Magazine as they cover these topics routinely.  Example:  Ultima has a 140 cubic inch V-Twin engine you can slip into your bike's frame... it's a real beast!  They also have 80" to 130" cubic inch engines too.






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© by James Russell.  All Rights Reserved.  Posted on: Reprint Rights:  Enthusiasts and Motorcycle Dealers may post and reprint this article and use it to help them sell motorcycles as long as they do not make any changes to the document. and includes this copyright notice entirely.