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
racerx573

426 overheating Badly

3 posts in this topic

Here's my scenario, I have the engine in a quad frame for MX.

I have a 42 pilot

172 Main

Needle is on the 3rd clip (stock needle)

It's ported, K&N filter, 13:1 piston, 450 cam mod.

Wet sump kit

It has no response off the bottom end, but screams once it is wound it, but takes a while to get there. I just checked out all the jetting guides and printed them out to try some different combos.

My plug is burning kind of a grayish brown, and my exhaust tip is a little white, so she was running lean.

When I come off the track the coolant is down to the fins in the top of the rad, and she is blowing steam furiously.

I installed a catch bottle, and a high pressure radiator cap.

I figured since it was running like that I may have a leaky head gasket, so a new one is on the way, and there was a minute amount of drip from my weep hole, so I ordered a new mechanical seal.

I am going to try all of this, and run the jetting I was running before.

But if anyone else has any insight, I would greatly appreciate it.

Share this post


Link to post
Share on other sites

First, confirm that the flywheel key is intact by checking actual TDC through the spark plug hole against the timing marks. Then check the cam timing.

Share this post


Link to post
Share on other sites

I've got the whole head off right now still, I am gonna check all the timing and whatnot in reference to the YZ450 cam mod thread. I bought the engine used, so something could be out of line. What should I check for when checking the flywheel? Thanks for the info.

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