21st Century Tuning for Vintage Pavement 2-Cycles


There is no such thing as the “average” vintage 2-cycle pavement bike … or rider.  With that we have categories that cover “most” riders.  Knowing the category of rider you are helps to choose the right modifications to best suit your riding (and budget) needs.  Here is that list :


“Reliability” Rider – This is the most common kind of owner.  The biggest priorities are wide powerband, excellent “like stock” reliability, easy starting, and usually 91-octane pump gas.  This rider seldom runs at peak rpm, and rides with a mindset of not abusing perishable parts.

Competitive Rider -  This non-racing rider is fit and skilled, and wants a fast machine to match his skills.  While reliability is still important, he is willing to deal with a powerband that is a bit more “aggressive” than stock.  This category can generally be set up for 91-octane fuel.  This owner is happy to do the regular maintenance that that comes with running a vintage bike exceptionally hard.

Reliability Racer-  This racer enjoys the opportunity to run a vintage machine in a pavement race, but is more concerned about having a good time rather than winning.  This rider would rather choose a more subdued pace rather than an intense pace that can be abusive to perishable parts of his machine.

Competitive Racer -  This fit and skilled racer rides to win, and going “easy” on the bike is not a top priority.  He wants an aggressive powerband that delivers well at all RPMs.  This rider needs to expect to do regular maintenance and inspection work on all aspects of the bike.  This rider is okay running 100% race gas when racing.

Elite Racer -  This is a top-level pro or very aggressive racer that runs the bike as hard as it can be run.  This rider makes no effort at all to “go easy” on the bike, and demands everything it can offer most of the time.  This rider is okay with a high rpm oriented motor that requires plenty of shifting and clutching.  This bike should always be run on 100% race gas.


What is the Difference Between Tuning Today, and Tuning “Way Back When”


The building and tuning of vintage two strokes requires a whole different mindset (and priority set) than what has been used in the past … and here is why.


  During the 1970s & 80s, the primary focus of all engine mods for pavement 2-strokes was to get the maximum possible power that suited either drag racing or “sport-level” street riding.  During the 1970’s, 98 octane “premium” fuel was widely available, and during the 1980’s, 93-95 octane was also available …. without the numerous additives that we see in today’s “pump” gas (ethanol, oxygenates, etc).


  During those same 70s-80s years, pavement racing machinery was ridden by fit and younger riders that were ready to “flog” their machine to the very limits of mechanical abilities at every outing.  Few racers worried about failing a mechanical part, because the supply of replacement parts was plentiful … and relatively inexpensive.


  Fast forward to 2010+.   Riding and racing “easy to maintain” vintage two-strokes is still great fun.  However the pump gasolines available today are of much poorer quality … and the supply of affordable (internal moving) replacement parts are in much smaller quantity.  The result is, the way enthusiasts ride their vintage two strokes is changed … and the way the engines are tuned also needs to be changed.


  The new 21st Century  “tuning fashions” have become two-fold.

A)    Make the widest possible powerband that has “acceptable” top end power” …. and

B)    Make the greatest-possible “reliable” horsepower that can had “with the engine maintenance and fuel octane I can afford”.   Neither of these two priorities existed for competitive pavement riders of the 70s-80s, and so, no high-performance shops of the day did development work towards those ends.


About Perishability

   Anyone who wants the highest output Kawasaki H1 500 triple can easily build one to the widely available H1R Factory race team specifications…and you’re done.  The reason this setup is not commonly chosen is because the “rideability” (powerband) and reliability (crank life) of a top drawer H1R is horrendously poor.  H1Rs were designed and built to have “just enough” longevity to finish the race at hand … and no greater engine life than that was pursued.  The H1Rs factory racers were also designed to have the narrowest powerband that the pro-racer at hand was willing to tolerate….and those riders were often willing to tolerate “not much” in the way of powerband width.  In addition, “successful” H1Rs were fielded by race teams who adopted a “money and labor is no object” mindset.  Today, there are precious few H1 owners/racers with an unlimited parts supply and/or budget…. So building a true H1R to ride or race is questionably wise, practical …nor even fun.


  The technicians at Klemm Vintage have considerable street and track experience with all of the popular “sport” 2cycle street machines of the 70s & 80s.   However in the 1990-2010 era, we specialized in developing high performance 2-stroke PWC engines that had to make the widest possible powerbands (to accommodate a “no-gearbox” PWC driveline), as well as developing the highest possible performance that could be had on today’s 91-octane premium pump fuels.


    While air cooled vintage pavement 2-stroke engines are obviously different in many ways from more modern 2-stroke PWC engines … The technical rules that apply to reliability, wide power-band, and detonation resistance, are the same.  For our PWC development work, we used data gathering instruments and modifications that didn’t exist in the 70s/80s, to develop the high performance “91-octane safe” PWC two-stokes of the 21st century.  We believe that the combined experience of having mastered both genres, gives us the expertise to produce among the most reliable and effective vintage two-stroke pavement engines … anywhere.


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