YZ426 Parts Interchange?

Long story short, my brother's 2001 YZ426 threw a rod or something and basically exploded parts out the bottom of the engine. Tore it down, and the head is still in great shap, but that's about it. Cylinder skirt is cracked, piston is trash, crank and rod are broken, and you can almost put your fist through the hole in the cases. The transmission seems alright, but whoop-de-doo.

Anyway, I'm trying to piece together a motor for him. I found a bottom end off of a 2000 YZ426. Will this fit in his frame? If so, will his 2001 head fit on it? The Ebay bottom end needs a crank. Will a WR400 or 426 crank work? Which years will plug and play? How about pistons and cylinders?

Thanks for any advice I can get here. I know the 450's from 2006-up real well, but the 426's not so much.

The 2000 is completely interchangeable with the '01. The 400 crank bolts into the cases, but to use a 426 top end, you need a 426 rod installed. Better to stick with the 426 crank.

The 2000 is completely interchangeable with the '01. The 400 crank bolts into the cases, but to use a 426 top end, you need a 426 rod installed. Better to stick with the 426 crank.

Okay so i have a frame of an 00 model but i have no clue if the motor is an 01 will my clutch fit either crank please i need help bad. Thanks

The clutch doesn't go on the crankshaft, it's on the transmission main shaft.  The '00 model 426 used a square key to locate the balancer drive gear to the crank, while the '01 and later use a set of splines instead.  That's the only difference, and either crank will fit in any of the three years of YZ426 made.  If you use an '01-'02 crank, you have to also use the balancer drive gear from the same year and you're good.

I'm impressed that you trashed the bottom end that well but the head is ok. 

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