2000 Yz426 Engine Rebuild And Mods?

I have a quick question for people. My friend just bought a 2000 yz426. The previous owner didn't do much in the way of up-keep on the bike, and now my buddy is faced with a total engine rebuild. While he has the engine apart and the cranked ripped out, what are somethings we should look for when we put it back together? and what are some of the best mods we could do to the bike when we put it back together?

is the engine already apart? what blew?piston failure?main bearing failure?what happened?

Check the counterbalancer key, and since you've got it apart I'd replace it. Put an 03 YZ 450 exhaust cam in it, PM YZDAD1 and get his stroke/overbore treatment to turn it into a YZ 459, and get a Thunder Alley pipe for it.

Go one step farther than Cowboy, replace the crank half with a 01 crank and you will move to a splined counterbalancer gear.

Wouldn't that also require the other 01 counterbalancer parts though? It's been so long since there was any major discussion on the CB key I've forgot :)

Wouldn't that also require the other 01 counterbalancer parts though? It's been so long since there was any major discussion on the CB key I've forgot :D

I'd really like to know to as mine is just now ready to split the cases and could benefit at rebuild time :) .

At the time of the original post, only the bikes top-end was off. I guess the wrist pin went and the crank must be replaced. right now the crank is in the process of being split. My friend is also going to redo the top end (piston and rings). Its in at the shop right now getting fixed. I told him he should look into getting a newer decompression cam, but i was just wondering if there was a alternative to rebuilding the bike as a 426, or maybe into a 450. either way. to think all of this started cause my friends bike wasn't as fast as my 450r

PM YZDAD1 and have him do a +2mm overbore with a +2mm stroked crank for a YZ 459 like I stated earlier. You might be able to use a complete 450 crank, rod, cylinder, head, piston, and cams, but it would be expensive and I have no idea if it would work or not.

Regarding the CB gear besides the crank half, you should only need a new gear that is splined not keyed. I dont think the 450-426 crank swap is possible.

a 2mm overbore will make it 444cc's.

The two weak points on the 2000 are the clutch (get an aftermarket basket and do the 2001 update) and the CB key. I haven't had any problems with my stock CB key, but I'm going to replace it while I have the motor apart for piece of mind.

a 2mm overbore will make it 444cc's.

The two weak points on the 2000 are the clutch (get an aftermarket basket and do the 2001 update) and the CB key. I haven't had any problems with my stock CB key, but I'm going to replace it while I have the motor apart for piece of mind.

It is very easy to replace, should take an hour or two. There is usually no failure just clacking (there has been some failures just not too many) It will quieten the motor when changed. Still a mechanically loud motor though.

The 00 with the 01 clutch fix is a solid clutch, there is no need for the basket unless your stocker is trashed.

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