Saw flooding

[grantwolland]

I have an older Roper made craftsman 3.7 chainsaw that uses the walbro SDC 73 series carb(no high idle adjustment) problem is, it starts fine but when I pull the trigger to throttle it, it floods the saw and dies. I can keep it going if I remove the air filter and throttle it but fuel starts spitting back out the intake! I don't think it is a carb problem because I have another 3.7 saw that runs fine and I switched it's carb over to this saw and the problem remained. Am I overlooking a basic characteristic of a 2-cycle engine? is there too much crankcase pressure? Any help with this problem would be appreciated. The only difference between this saw and the other 3.7 is that it has 140 pounds of compression and the other one only has 100 pounds of compression.

 

[daemon2525]

Check that the reed valves are closing completely.
Sometimes they will get stuck open with a bit of debris. This will cause it
to blow gas out of the carb.

 

[grantwolland]

Thanks, Daemon! no sooner did I post this thread did I forget about mentioning the four reed valve on the saw. I looked up a website that was talking about 2 cycle engines and it mentioned that reed valves act as a check valve for the fuel/air mixture. I took the saw apart last night and found the bottom reed had broken completely off! Now I just need to find out where the rest of the reed went. Luckily the cylinder doesn't appear to be trashed so it shoulod be in the crankcase.