Hi
I have a problem with my 91 magnum 4 stroke.
Engine was run very good for last couple years. Last time
I did a mistake. I runned engine lean for about 10-15 min.
Engine was run, he was very hot and noise and was no power,
plane was fly slow. After I adjust a needle valve, engine was run
in normal temperate with no power, sounds differently.
After disassembling, i saw bad bearings. Now, I replaced bearings and connecting rod. I put engine together, and I try
to run, Engine started easy, but in hight RPM no power at all.
( looks like 20 size engine) Now , I dont know , I did some
mistake in assembling (timing), or i have to replace head gasket?
( because seems i have low compression on it) . If someone have experience on four stroke engines (assembling) , please
Let me know what to do.



Thanks

It would be best if you sent it back to Magnum! It sounds like you cooked it. They may replace it for free.

I'd check your timing and valve lash before I sent it in.