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
davcon

100 Hrs on an 08 - What would you replace?

14 posts in this topic

Mainly trail ridden by vet rider. Well maintained. Adjusted the valves twice but thats it. I ride out in the boonies where there is spotty cell service and would not want to push it back to the main road(s). Want to keep it reliable. What would you replace? Thanks!

Share this post


Link to post
Share on other sites

The timing chain absolutely.

How much total valve adjustment has been done? Two adjustments in 100 hours seems a bit excessive.

Share this post


Link to post
Share on other sites

I had a YZ426 for eight years that did not require any valve adjustments whatsoever, although I checked several times. It needed no maintenance or repairs during my time of ownership, and was still strong when I sold it, with no clicks, clatters, smoke, or drips at all, and was still a one-kick starter.

It probably wouldn't hurt to replace the timing chain, as stock Yamaha chains are inexpensive.

1 person likes this

Share this post


Link to post
Share on other sites
The timing chain absolutely.

How much total valve adjustment has been done? Two adjustments in 100 hours seems a bit excessive.

Good catch Gray! Verifying my records, the left and middle intake required one increment at 4.5 hrs. I checked them again at 32 hrs, no adustment required. Any thoughts on a new piston and rings?

Share this post


Link to post
Share on other sites

Piston and rings won't hurt anything except your wallet, and you might actually prevent a problem down the road by doing it. On the other hand, my '03 had well over 3 times that on it when it was sold. You just never know. If you're inclined, open it up and have a look.

Share this post


Link to post
Share on other sites

Yeah but... your piston may or may not make it for hundreds of hours. You could be putting your motor at risk. If your just putting around it may last, or not. A new piston, cam chain and gaskets can cost under 200, if you do it youself.

Share this post


Link to post
Share on other sites
The timing chain absolutely.

How much total valve adjustment has been done? Two adjustments in 100 hours seems a bit excessive.

Im guessing the timing chain has a good chance of breaking after 100 hours, or does it stretch excessively or something?

Share this post


Link to post
Share on other sites

I don't recall ever seeing one break, but they can do one of two things:

They can start binding up, which causes "kinks" to form on the slack side. This can prevent the chain tensioner from tightening it because there may not be sufficient spring force to press the kinks out. That in turn can cause the chain to suddenly skip one or more teeth at low speed, or when starting or stalling.

The chain will, like any other chain, increase its pitch as it wears (called "stretching", although there is very very little true plastic stretch involved), and that increases the risk of skipping time and seriously damaging the engine, and it accelerates wear on the sprockets, especially on the crank. The bad part of that last, of course, is that the crank sprocket is cut directly on the left crank axle, and can't be replaced independently of that half of the crank.

Share this post


Link to post
Share on other sites

Is it worth changing just the rings and not the piston after 100 Hrs? I have 2 sets of them in the spares kit.

Share this post


Link to post
Share on other sites

my manual says to replace the cams and cam chain together. it makes sense doing chain and sprockets but is this true with the cams too?

Edited by danZ73
misspelling

Share this post


Link to post
Share on other sites

The sprockets are only replaceable by replacing the cams. I have never replaced them as a matter of course along with a chain, only if the cam or sprocket was actually in need of it.

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