rzresurrection

Holy crap. Who ever talked about pumping up the case to find a COOLANT leak? Read the post first instead of going off half cocked about what you THINK you read. Let me say it again incase you you mis read this one more time. Do an effin leakdown test after you do anything - to verify there is not an air leak anywhere. THIS IS NOT TO CHECK THE COOLANT SYSTEM fora leak. FFS

+10000

No problem. I know my way around these engines well enough. I don't know everything, but always willing to learn more.

The pressure test is to make sure you don't have any air leaks anywhere else - I don't get the feeling that the OP has ever leak down tested the engine. I didn't mean it as a test for the cooling system, just as an overall precaution afterwards

My comment was directed to mike0chek. I should have quoted his post Check the cap, check the head orings. Do a leakdown test afterwards. My $0.02

You mean coolant system is cavitating? Hydro locking breaks breaks con rods, pistons, etc

True enough. Good one.

If you have a failed head oring, you are essentially air-locking the cooling space around the head by continually forcing in air/fuel mix into that space. By doing this you've effectively reduced the cooling capacity of your system causing it to overheat.

Starter fluid - not recommended. You need a proper leakdown test. Not super hard to build. You can build a cheap leakdown tester. Here is a pic of mine. If you're serious about 2 strokes a leakdown tester is a must. Easy and cheap to make. Pull the engine and remove the flywheel. Plug all the entry and exit ways for the engine. White parts go into the intake boots, rubbers and plates cover the exhaust ports. Pump air into the schrader valve (6psi Max) and spray soapy water around the sealing surfaces. If you have leaks, you will have bubbles. That's the short version

Puke out the coolant and what cools the engine? No coolant = overheating

The ORing isn't sealing 100% and the pressure created by the piston compressing the fuel/air mix gets pushed into the cooling system at the point of the failed oring. This forces the coolant out of the system thru the overflow

Most likely a head oring issue causing your cooling leak Question is why did the oring fail? You can change the orings out, but do a leakdown test afterwards to make sure that you didn't develop an air leak somewhere that caused the engine to run hot, overheat and kill the orings on the head.

Oh, ok. If it's puking coolant then you are pressurizing the coolant system and odds are its coming from the overflow.

Are you saying that it overflows coolant?

If you've ruled out the cooling system (impeller, plugged rad, low coolant etc). Then it has to be excessive heat generation. Excessive heat from a lean condition - air leak somewhere. I'd leak test it before you pull the head. You need the head on to leak test it anyways, so leave it on and pressurize it. My guess is that it won't be the head. Typically you'd get coolant out the overflow if it was.