I have a 300 Xpress that was gettting rel hard to start last year. I finally took the cylinder off and had it bored and a new piston and rings. I went throught the carb with a kit and put everything back together. It has much more compression. The thing is still hard to start. I can crank it over for several minutes and it will finally fire off slowly but after it starts and smokes to high heaven, it will start like a new one every time. I ran it donw the road and after about a mile, it bogged down and quit. It will not start again. I smell fuel in the exhaust and it has fire. I have read a lot about similar problems but do not seem to find a single resolution. I am al witts end. This is not my first 2 stroke. I raced motocross for 20 years all the wat to semi pro AMA and this simple 2 stroke is about to ge the best of me.

Dewey

Georgetown, Texas

 

Recheck your compression. If compression is above 120 psi and you've eliminated the carb,fuel supply or spark as a source of the problem and you didn't replace the crank seals as a lot of people do,this could be the problem. You have to have good top end compression plus bottom end compression for the air,fuel and oil mixture to atomize properly and shoot up the transfer ports to the top of the piston for ignition.