250-500cc Wr 250 Engine Rebuild Advice

Hey,

I am rebuilding my recently acquired WR 250 and have a couple of engine questions.
The bike is in the process of being rebuild / supermoto'd so i will get some photos up soon of the project.

My first and foremost question is about the spacer that sits behind the primary gear on the end of the crank shaft. On disassemble there was no o ring, and on all the parts drawings i cant see an o ring - however on the other 2 strokes i have built there always has been to stop air getting sucked through the spacer and into the crank case.
I have attached a photo of an exploded diagram where i expected to see an o ring.

Secondly, when doing a leak test i left the power valve covers off. When i pressurize the engine it leaks straight out through the power valve o ring seals.
It has new o rings so i assume they're not an air tight seal so i can put the power valve covers on and do the test again?

Hope that all makes sense

Cheers,
Dan

For anyone interested, or that stumbles across this thread in the future…

As previous 2 stroke I have rebuild have had an o ring on this spacer - I assume this one should

I have a couple of o ring sizes to try tomorrow and will update with results

No oring necessary.

Thanks Rancher1,

I bolted everything together and pressure tested the engine with no o ring on the spacer.

Soapy water around the bolted up spacer / primary crank gear and no bubbles.

Hi Dan, I've re-read my engine rebuild post and also checked the owner manual and parts diagram of the engine and there is no O ring on the crankshaft end, there are flat surfaces that makes the seal, make sure those surfaces are clean and flat and there should not be any leaks once torqued town to the correct specs. You could put a tiny bit of some thick grease on those contact surfaces if you like to probably improve sealing, but it's normally not needed.

Cheers .

Cheers for getting back to me Hurky,

I have got the engine back together now and its back in the bike and running well.

Thanks for the infomation, i will start a new thread with some photos of my supermoto project

Link to the project in supermoto section if anyone is interested:

WR 250 supermoto project | Cafe Husky

Hi
No o ring required and those o-rings on the exhaust valve are pesky if they don’t seat correctly you can get issues we have to check double check and triple check they seat right
Glad your engine is back together and running