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
88motohead88

2006 yz450f piston markings

13 posts in this topic

The piston is hitting the head is what's happening.  As it's only hitting on the exhaust side, it could be too much rock/tilt at TDC due to excessive piston clearance, or a lot of carbon on the head on that side.  Otherwise, it would be due to inadequate deck clearance (the distance between the top of the piston and the top of the cylinder at TDC).

Share this post


Link to post
Share on other sites

Sorry what I'm trying to say is the piston clearance you mentioned shouldn't be excessive because it's a brand new cylinder and piston right?

Share this post


Link to post
Share on other sites

Sorry what I'm trying to say is the piston clearance you mentioned shouldn't be excessive because it's a brand new cylinder and piston right?

You may have some mismatched parts there. You should contact the manufacturer with pictures.

Share this post


Link to post
Share on other sites

Where did you get the 'new' cylinder from?  Or was it a remanufactured cylinder?  If it's a reman, I wouldn't be surprised if they decked the cylinder and/or the head and took too much off.  Regardless, you should start by measuring the deck clearance.

Share this post


Link to post
Share on other sites

It was from cylinder works. Brand new. So if I run this like this now that the piston and head is "shaved itself " basically by am I gonna blow it up? It ran great but the rod broke, I've got a new used bottom end.

Share this post


Link to post
Share on other sites

The head and piston show the signs of contact, I'm wondering if the damage has been done won't it be ok now?

Definitely not. You do not have enough clearance and I would not trust the beating the piston took as it being clearanced now.

Share this post


Link to post
Share on other sites

Ok any suggestions?

If everything else is okay you could have the piston shaved down to make the proper clearence.

You should however find out why it hit. Was the head decked or material taken off from it.

Share this post


Link to post
Share on other sites

Start with the piston. measure from the pin bore to the top of the crown and compare to the original.

1 person likes this

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