Modern four-stroke engines are remarkable things. These technological marvels are the ultimate in performance and reliability for average riders as well as racers. Large doses of torque and linear power delivery make four-strokes a natural for ATV racing. In recent years the weight and reliability of these engines have made great strides and today, four strokes are the obvious choice.

Developing four-stroke power, however, is a study in incrementalism. All of the reciprocating parts create friction and heat that detract from performance. As a result of this dynamic, building up the power is best approached in stages.

These engines are, in essence, many parts that together create a whole. If all the parts work in unison and in concert, large increases in reliable power occur. If only a few pieces of the whole are installed, you may create more problems than you will solve. All the pieces have to work together or you will concentrate stress loads and other negatives into specific areas. This can end up in CEF (Catastrophic Engine Failure).

At Yoshimura, we have been building four-stroke racing engines for over 50 years. We understand that your engine is the sum of many parts. We do not simply throw a big cam in, pop up the compression, and create a time bomb. Depending on which stage of engine modification you choose, we build power at self-sustaining, balanced levels.

We have our own in-house Isotropic Surface Finishing Process (ISF) department where we can blueprint your engines gear-sets just like Formula-1 machines. This technology not only let's your engine run “freer”, but also lowers operating temperatures through decreased friction and proper interaction of reciprocating parts. We also have twelve Dyno cells (including two state of the art Onno-Soki units) and advanced computer diagnostics in everything from flow to metallurgical failure rates. There is no guessing here.