Let me preface this by saying it was recently in a crash. Here's what its running on. 10% and 20% pro pattern fuel....same results. APC 12-7 prop. I used to get around 10,000 RPM's with this set up. I have completely broken the engine down and mic'd the crank which appears to be straight and true. Replaced EVERY rubber O-Ring, replaced the head gasket. added sealant to all mating surfaces. Checked the timing 3 times, Checked the valve lash multiple times.
It will start cold fine but has a lot of smoke regardless of where I set the mixture needle. It used to not do this. I can set the low end to get a good transitions but it stil seems very smokey compared to what it used to be. When I run it up to max power and lean it out i get about 9800 RPM which is great but then something instantly changes and what little smoke was there goes away and it drop to 8000 RPM and stays here now matter what I change on the needle. From then on as long is its warm the engine won't go past 8. If I let it cool down and start over it does the same thing. Initially peaking at 10 then dropping back down. If I let it idle for 15 seconds or so and then goose it, it will initially peak to 10 and drop right back down. The high speed need doesn't seem to do anything much in the way of adjustment of the RPM's until I hit so lean that it just dies.

Help Please

So frustrated.