I have a 2 cycle gas blower/vacuum. It is a Poulan and I have owned it for about 6 years. After the first two years the engine lost all compression. The cylinder head was scored. I replaced the cylinder head, piston, and ring and have been using it ever since. It works adequately, starts quickly, and runs smoothly. I have put about 48 tanks of fuel through it.

However, I have noticed that it does not rev up as high as it did originally. I have also noticed that if I run it with the air filter off so I can observe the venturi, at fully wide open throttle I see vapor escaping through the air intake. The flow should be in the opposite direction. What could be the problem? Could it be timing? I have not measured compression but from the resistance I feel by pulling the starter rope, it appears adequate to me. Furthermore it will run at a very low idle speed like an engine with decent compression should. I have always used outboard motor oil in my gas mixture. I have done that for years in my other 2 cycle engines. One is 22 years old while the other is at least 12 years old and both run fine. I have already tried adjusting the high speed mixture screw.

 

Sounds like a clog muffler,take the muffler off and check the spark arrester screen, in the muffler.Hope this helps

Jerry

 

I agree, sounds like your exhaust is clogging.

 

Just before I drifted off to sleep last night I also thought of a partially clogged muffler. Sounds like a very reasonable explanation to me. Thanks for confirming. Will let you know what happens when I get around to burning it clean.

 

Removed the muffler and cooked it with a torch. Engine runs full speed now and does not puke air- fuel mixture out of venturi.