I began racing motocross on small-bore four-strokes, and lately I find myself drawn to those roots. These new-generation 250cc four-stroke motocrossers are ridiculously fun, despite not being targeted at guys my size. I ride on track days more than I actually race, so the fact that I'd get killed on a start against 450s in the age group classes isn't much of a factor. But when we conceived this group of big-bore projects, we decided each should go to a race or special event where it would be pushed hard. The last thing you want when buying performance engine parts is a short fuse. OK, if I'm racing, then the outlook on small-bore bikes is different. I'm not a moto hero and can't give up a ton of ground on the start, so I needed to go big. I turned to Rick Peterson Motorsports (RPM's), which creates a Honda CRF302R (or X) by combining a stroked crank with a billet Ice Cube big-bore cylinder.
Since splitting the engine cases is mandatory on a Honda CRF250R for either the bore or the stroke, neither the cost nor the labor is for the faint of heart or thin of wallet. On the plus side, though, the CRF250R's 32 or 33 stock horsepower balloons up to nearly 40 as a result of the displacement increase, and that boost carries through the powerband. The added power must be directly related to the engine size, since little else is changed. The compression is bumped a bit, but the carburetor and valve train remain stock. RPM's also gives exhaust recommendations for each brand's engine kit, and the Honda called for a Leo Vince for all-around performance, the FMF for maximum high-rpm pull or the Pro Circuit for optimum bottom power. We liked the description of the LV pipe and tried it. There are other options, such as cams and porting, but we didn't feel any need for them. It wasn't that long ago that 250cc two-stroke motocrossers didn't make 40 ponies, and they all weighed more than a Honda CRF250R four-stroke!
The kit is complete, including machined head stays to accommodate the taller top end and extensive paperwork that lists all costs and outlines break-in and running suggestions. We bolted in our engine, added the suggested jets to the carburetor and went to the track.
There is a slight increase in compression feel when kicking over the bike, but it isn't an issue. Break-in went according to plan, and the 302 is amazing. It barks hard from low in the rpm range; the middle rpm range is more muscular by far but still as controllable and fun as stock. Let the bike rev-something you do a lot less of on the 302-and it rips with as much as 8 more horsepower than stock. The actual quantity of power feels roughly equal to that of a Honda CRF450X but with less bottom while requiring more rpm. It takes a little while to grasp how to ride the bike most effectively. Corners that were taken in second with a quick shift on the exit are now entered and exited in third gear. You tackle rutted turns a gear high as you do on a 450 and accelerate through the turns at a far lower rpm than with a stock 250.
The same is true with jumps that require you to shift right beforehand in order to clear them on a stock 250. On the 302 you shift earlier and let the power pull all the way up the face. This bike is not a hot-rod 250. It is a different animal that falls between a 250 and a 450-a place we like. As powerful as the 302 is, it remains usable and easy to manage like a 250. As effective as modern 450s are, they can be demanding to ride, and many pilots find them overkill. The biggest difference for me is how much faster I can ride into and out of turns. I'm not sure I am faster on the 302, but I certainly feel quicker and can last longer.