I have bought a trx 125 for my son as he has the adrenalin bug and wants to go quad biking, the carb keeps throwing petrol out of the overflow bowl, i have stripped the carb down several times and cleaned the parts methodically but on each occaision when i test ride the machine the fuel just flows freely again. What could be the problem?.

 

Has to be the needle valve, either dirt or worn.

 

What ^^^ he said.

 

I had a trx250 utility. Had the same problem right after stripping and cleaning the carb. My needle valve was good and clean. Mine had a plastic float and no metal tab to adjust float height. So I figured it must be the float. Bought a new float and no more problem. Worked for me. Just my 2 cents. Good Luck.

 

Yeah I would go with the needle valve sticking or bent. If that checks out ok then make sure the float has a 2mm gap in the tab so it doesn't bottom. Also make sure there ar no holes in the float. An improper working float will cause the bowl to fill up and have the same symptoms you mentioned.