Deja Vu... Didn't we go through this before?

It is possible someone modified the intake timing by either grinding the port or cutting the piston skirt. Don't worry about the intake timing and just get the exhaust timing up to 150 degrees or so.

Your engine is down on power compared even to fairly stock 25/30cc Homelites I have had. It is not hard to get them to turn a 16 x 8 at over 8500 rpms with just a little porting if things are right. Check your ring gap. It should be about the width of a piece of thick paper at the most. I am betting it is much larger than that, and giving away power. .003" is the spec if you have feeler gauges. Frank Bowman's rings are actually set at ZERO ring gap.... Note that you also need at least an 11mm carb and a free breathing muffler to make power.

By the way, I have a fully modified Homelite 30cc that turns an APC 16 x 8 at 9400 rpms. A friend has a 25cc that I did only moderate mods to and it turns the same prop at 8500 plus.

AV8TOR