MOD SQUAD: Yamaha YZ277cc Big-Bore Kit

RPM'S Yamaha YZ277cc Big-Bore Kit

Application: All Yamaha YZ250Fs

Price: $1800.00

Rating: 9

A few months ago we tested a full-blown Yamaha YZ302 from Rick Petersen Motorsports and reported that it was the fastest YZ250F that we had ever tested. After Rick repossessed his hot-rodded Yamaha from us, we found ourselves missing the extra grunt that the 302 had, so we begged him to work his magic on our YZ250F test bike.

Always one to work the angles, Rick suggested that we try out his more affordable 277cc kit instead. “I like to call the 277cc kit the perfect mod for cheaters with a conscience,” he said. Well, beggars can't be choosers, so we shipped our test bike off to grow 25 or so cubic centimeters.

While the YZ277 doesn't exhibit the same arm-jerking power that the 302cc kit did, we must admit that on hard-packed or more wide-open tracks, it was hard to tell the difference between the two. Obviously better than stock, the 277cc kit is nearly as good as the 302cc kit in certain conditions. The powerband is similar to that of the stock engine, but power is boosted noticeably throughout the rpm range. Low-end roll-on power is most improved, and the modified bike is easier to get over seat-bounce style obstacles on tight courses.

How does the 277cc kit compare to, say, a stock bike with a pipe and aftermarket airbox? It's not even close. There is no replacement for displacement, and if you are looking to get some quality added power out of your Yamaha YZ250F, going bigger is the best way to get it.

– Donn Maeda

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TWMX test rider Michael Young was impressed with the added power that the RPMs 277cc kit gave our Yamaha YZ250F, and raved most about the bike's added low-end throttle response.