Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/128325
Look carefully: the bike on top is the YZ278F w ith the stock appearing motor, while on the 302's motor below, you ca n se e the aluminum spa ce r between the crankcase and the cylinder. Riding the RPMs bikes was a good excuse to get my buddy Dana Legere, one of Cycle News' ad hacks and an expert-level rider, out of the office. We brought along ou r "con tro l bike," an '04 'fZ250F with a Ti Force exhaust system on it. After getting used to the stock bike on the Lake Elsinore track, we busted out the big bores. YZ27BF The 278 is the largest displacement kit that RPM installs in a 250F that still looks completely stock from the outside. The 278 is a 262cc big bore (anothe r option from RPMs, 2mm over) w ith a 3mm stroker crank. RPMs relocates the crankpin 1.5mm farther from the crank's centerline to achieve this. It doesn't re q uire a spacer be tween the crankcase and cylinder because the deck of the piston is trimmed for proper piston-tohead clearance at TDC. Additionally, the crank flywheels are tumed down so that the skirt of the piston doesn't hit the cran k at BDC. The $2278 price tag includes a spare 79mm piston kit, head and base gaskets. The VZ278F was fitted w ith a Yoshimura TRS Titanium exhaust system, TAG Metals handlebars and upper/lower triple clamps , and revaJved suspension by Pro Valve utilizing Enzo re mote reservoirs. The cool thing about the 278 is that the lightened flywheels make the bike extremely snappy, allowing the-motor to rev lightning fast at the flick of the throttle. The jetting news.com was excellent on the 278 with no noticeable stumbles anywhere in the rev range. Dana felt that the 278 was the perfect setup for· tighter tracks, especially where you need the motor to pick up the revs very quickly out of a corner to clear a jump. The motor didn't vibrate any more than the stock VZ's does. As far as the power is concemed, when Dana and I hopped back and forth between the stocker and the 278, it was extremely apparent that the modified bike has a heck of a lot more power. The 278 is a great bike for anyone looking for a snap py, quick-rewing weapon for tight and jumpy tracks, but for those of you looking for something that pulls harder, longer; read be low. YZ3 0 2 F The 302 is the way to go; what's $600 more when you're already going this over-the-top? The 302 uses the same 2mm over bore as the 262 and 278, but this baby is stroked bigtime. The 302 is stroked 8m m by relocating the crankpin hole 4mm farther from center and then adding an 8mm longer rod. This is where the motor gets a bit more radical. To achieve clearance, a 12m m thick spacer is inserted between the crankcase and cylinder. There went that "sle e pe r " look. Additionally, the setup requires a 24mm longer cam chain - that Peterson has custom made - and longer guides , and the upper motor mounts are shorter. RPMs has been making the 302 for only th ree years , but it CYC LE NEWS • MAY 26, 2004 53