Yamaha YZ250 mods

The YZ250 motorcross bike can be tamed a little with some mods. The standard close-ratio transmission is geared for about 73mph. The engine spins up in an instant delivering about 48bhp. Between the 2T and 4T bikes, the transmissions are similar in design. The WR 4T bikes have a wide ratio gearset, and the YZ 2T and YZF 4T share similar short-ratio motorcross aimed gearsets. Which means you can swap WR into almost any Yamaha engine - early 4T but any 2T engine - since the design of all YZ engine internals have been the same for 20years. WR400 and WR426 transmissions swap directly into a YZ250. The WR450 needs some modifications.
I opted to change the whole gearset, giving shorter 1st, 2nd and 3rd, but longer 4th and 5th. Top speed is about 88mph now. The longer 5th gear is good for road sections. With the heavier flywheel, it does soften the power delivery while improving some torque at low RPM.
The bike does not come with a battery, and the stator can't support any sort of battery charging, without buying a larger stator with a charging coil. So I've chosen to fit a lithium battery, mounted on the fork yokes and wired into some basic tail and spot lights. The battery should last long enough for a days ride, and it doesn't lose voltage as charge drops. Plus the battery weighs just 480 grams.

Видео Yamaha YZ250 mods канала Lost The Plot