HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
yamon

2000 yz 426 motor knock

5 posts in this topic

2000 yz 426 has a motor knock. It sounds like its coming from the counter shaft balancer and water pump area. Any ideas.

Share this post


Link to post
Share on other sites

It's a bad key on the crankshaft. There are two gears on the right end of the crankshaft. The outer one drives the clutch assembly, and is secured to the shaft with splines. Right behind that gear is another one which drives the counter balancer. That second gear is held in place on the shaft with a key. The key is the same part from the older YZ400F, leading some people to believe that's it's not strong enough to handle the increased "thump" of the 426.

The key cracks, deforms, or wears down, causing the counter balancer drive gear to have some slop in the crankshaft. This slop sounds like a fairly loud "clack, clack, clack" at idle, when the rotational velocity of the crank shaft is "pulsing". The sound goes away when you get on the gas, but it won't be long before the key fails completely, or the nut securing both gears to the crankshaft loosens to the point that something horrible happens in the right side of the crank case.

The cheap fix is to replace the key with either the stock part, or a longer, thicker piece of key stock.

The expensive fix is to replace the crank shaft and counterbalancer drive gear with the parts from a 2001 426, which used splines to secure the gear instead of the key.

Share this post


Link to post
Share on other sites

Do you know if a 02' crankshaft will work? I've found one that has a good price tag on it. I have a 2000 426 with the same problem...I think. I haven't torn it apart yet, but it sounds like the same problem I have. I'd rather replace/update the crankshaft while I have it apart if this 02' crankshaft will work. Any info would be greatly appreciated. :thumbsup:

Share this post


Link to post
Share on other sites

You can replace the right side of the crank with an 01 or 02 unit, but I'm not sure how much worked is involed in doing it. Send a PM to Hick, he'll know.

Share this post


Link to post
Share on other sites

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
Sign in to follow this  
Followers 0