Destroyed head on 2007 WR250F-- what year/ model heads will bolt on?

(Yes, I did a search...)

Broke middle intake valve on WR250F-- bounced around and took out all 5 seats.

What heads will bolt on?

All 2007-2013 WR250F heads. What about other years of WR?

How about YZ heads bolting on?-- no concern with AIS system, it has been removed.

I'm looking for longevity in rebuilding this motor. This thing has been plated and run on the highway (not its intended purpose, I know).

Thinking about splitting the cases and putting taller 4th and 5th gear from earlier WR's in. (Reducing highway rpm)

Possible 290 kit - run with 1 tooth taller countershaft sprocket (again, reducing highway rpm)

Spoke with EDco (Engine Dynamics) today. The cost of rebuilding my head is probably more than it is worth. Spoke with them regarding longevity. They suggested steel valves and springs. Said that steel could be run with stock seats. I know this topic has been beat to death-- Ti vs. SS. As a material, it seems that SS would yield (stretch) where Ti would shear (break). Something about the modulus of elasticity..... Not concerned with all out performance, just wanting to avoid a repeat of a destroyed head. OEM valves are expensive and OEM springs are cheap, SS valves are cheap, and springs are expensive... Looking to avoid catastrophic failure.

SS valves and longer intervals or OEM Ti valve and a regular replacement schedule?

Remember, this motor (although it wasn't intended for it) may be spun on the highway 65mph for 60 miles!

I know some of you will tell me to buy a 450 or an XR400-- its not going to happen-- I only ask that we keep suggestions, comments, on topic and based on first hand experience, not forum reading.

Thanks,

Murph

Every bit of engine internals will interchange on all 250F YZ's and WR's from 2001 to 2011. The head casting is different on the '10 and later YZ's but all of the internals are the same. It's just a simple matter of parts swapping to build what you want.

Pulled from another thread. Wasn't there a combustion chamber change on the YZ's when they bumped the compression?

Edited by MurphSC

Looks like 2002 YZ heads use a slightly different carb boot-- clamps on versus bolt on.image.jpg

101 views and no response......

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