Aluminum chunks

I've got a 98 YZ400F that I started to have an intermittent clunking after i rode it last. Asked some questions and people said to check the keyways and balancer. I have the bike stripped to the point of having all the outside covers off and getting ready to pull the clutch basket after I get the tool. I have found nothing at the bottom of the case but I did find chunks stuck in the gear attacked to the back of the clutch basket and a small pile of chunks in the void behind the cylinder and clutch at the top of the case. The basket seems to have a lot of play and I'm not sure what is normal. Guess I'll find out after that basket comes out. Any thoughts on other pieces that are aluminum on that side. I can only think of the clutch parts. And there was no chunks in the oil filter or oil after drained. Thanks.


If the basket has rotational play between it and the driven gear, That is, you can turn the basket back and forth some on the gear, that usually means that the torsional cushion unit inside the assembly is beat up.  On the 400, the drive cushion was made up of springs, like the center of a typical car clutch disk.  These get fatigued over time, and then break, and then things go downhill fairly fast.


Unfortunately, the only choice is replaing the whole thing with a new factory basket assembly. 


While you're in there, check the crankshaft drive gear nut.  If it's even a little loose, check and/or replace the key that locates the balancer shaft drive gear.

Rotational play seems ok but i have play like when you test a ball joint top to bottom. 

You mean you can move it in and out on the shaft, up and down on the shaft, or the whole shaft moves one of those two ways?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now