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SSracingNY
11-29-2003, 05:23 PM
Hey, Im looking for a 400ex for around $2600 but my question is, whats these 426 conversions im reading about. There are a lot of threads about quads having a yz426 conversion. What does this consist of? Like are motor mounts moved, different frame. Whats involved. That mean there will be a radiator needed to be mounted?
Chanman420q
11-29-2003, 09:26 PM
well theres 2 types of 426 kits..... the first one is a 88mm piston in the 400ex engine, this is a .120 over bore.

The other one is the your talking about. Its a Yamaha YZ426F engine that they put into a 400ex frame. Yes u need diffrant motor mounts, u need to mount brackets for a radiator and an oil tank. You also need a kick starter extention so it clears the frame. Then of couse you have to buy a special pipe for it too. These Engines in stock form are no match for heavily modded 400ex engines. OUTLAWEX on here did this conversion and he had a 400ex that was pistoned, pipped, cammed, ported etc etc and he said that the YZF engine would run circles around his old EX.
Ryan
11-29-2003, 10:51 PM
Originally posted by Chanman420q
well theres 2 types of 426 kits..... the first one is a 88mm piston in the 400ex engine, this is a .120 over bore.

The other one is the your talking about. Its a Yamaha YZ426F engine that they put into a 400ex frame. Yes u need diffrant motor mounts, u need to mount brackets for a radiator and an oil tank. You also need a kick starter extention so it clears the frame. Then of couse you have to buy a special pipe for it too. These Engines in stock form are no match for heavily modded 400ex engines. OUTLAWEX on here did this conversion and he had a 400ex that was pistoned, pipped, cammed, ported etc etc and he said that the YZF engine would run circles around his old EX.

Hes right.

But a few flaws..... As far as I know, they don't make a YZF426 anymore. They now have a YZF450. Which has a decompression release so you won't have to worry about hard startings when the engine is hot with the YZF426. Kicking a hot thumper over isn't easy without a hot start!

Also, some people use the CRF450R engine in a atv chassis. I've seen these put into stock 400ex chassis's as well. But as Chanman420q said, there is alot of fabricating involved.