Converted a 25cc Poulan trimmer for my 60 size Big Stick. After running it on the test stand, felt the compression was low. Pulled the jug and found a score in the piston from some object passing through. Since I had the conversion and the fitment to the Stick all worked out, I headed to Walmart to buy a $68 blower. I planed on basically combining the two engines as I really did not want to machine another prop hub for the long shaft blower. After breaking down both engines, I looked carefully at the parts just to be sure all was compatible. Flywheels had the key in the same position, so could use the already machined flywheel. What I did find was the crank pins were in different positions. With the key way of both cranks in the 12 oclock positions the blowers pin was closer to TDC a good bit as opposed to the trimmer. Reassembled the blower engine with the trimmer crank. Also found out not to mix the modules as they are "timed" to their respective cranks. The trimmer has a white band around the plug wire, green for the blower. I wound up with a real sweet running 25. Will idle all day @ 2100, turns a 14x6 over 10,000. Yeah I know the props small but thats all the clearence I have, Ill just let it turn. Might be able to sneak in a 15x6 with bigger wheels. A friend converted the same blower and although it ran well it never seemed to have much power. I guess this is why. Moral of this rather long story is there are subtle differences, with in engine families. Mix parts carefully!

I just found something interesting playing with the poulan's... I have 4 Poulan 21's apart on the bench, I've been porting them one by one while I clean them up to sell them. 3 of these started at 115-120* exhaust timing, one had a bigger exhaust port (factory) pretty much looked like the ones I'd just ported but factory instead of modified, stuck the degree wheel on the thing and it's 138-140*, the other odd thing about this one is it has 2 transfer ports instead of the normal 4...

anyway, the plan is to run these engines tomorrow, I'll see how they run...