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
danzick

10 450 valve to piston contanct

3 posts in this topic

so I bought a used 2010 450 during the fall. I threw it in the shed during snowmobiling season. Well i decided to take it out and take it apart and rebuild it fresh for this coming season. I pull the head to find what looks like all 4 valves hit the piston, but it looks like they only hit just once. Did the previous owner not set the timing right before trying to start it? I would think if they hit while it was running, there would be more damage. bike ran fine when I tore it down. I put water in all of the ports to see if the valves leaked at all, but the valves didnt leak, so I dont think they are bent. Another mystery, I see its a vertex piston, and it has a cylinder works cylinder. It appears to me that the companies are linked in some way. Im wondering if he had a bad issue and lost the factory piston and cylinder. Do some people order a new cylinder while they are doing a piston? I never have. Just trying to clear up a few mysteries about this bike. I guess one plus, the valves were in spec.

 

IMAG0255_zpse07fdcf1.jpg

 

 

Share this post


Link to post
Share on other sites

What it looks like is that the piston was installed backward.  It looks as if the valves overhung the edges of the cutouts and contacted them.  The flycuts are centered differently for each pair of valves, and a reversed piston looks like the most likely cause of the valve contact.

 

What may have caused this is that arrow mark.  The OEM Yamaha piston is stamped with an "F" that belongs toward the front.  The majority of aftermarket pistons are made with marks that go toward the exhaust side of the engine, and judging by the cutouts on this one, I would say that it was marked with the arrow to be facing the exhaust side.  That, of course, is the rear on this particular engine, so there may have been some confusion about this point when it was assembled.

1 person likes this

Share this post


Link to post
Share on other sites

I agree. A friend of mine and I were looking at it, and that is what we came up with as well. Probably used to having the exhaust side towards the front of the bike, so they installed it backwards. Thanks! just wanted to make sure everything was ok before putting a brand new piston in it. Still wondering why he had to buy a new cylinder.

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