I have a 125cc GY6 engine which was purchased from Ebay for a transplant the problem I have is that when using the correct carb it starts but will only idle. As soon as you touch the throttle it dies. The carb has been off and cleaned twice and settings checked, but still no joy, I have a 50cc GY6 carb and decided to try that knowing it might not even start as not enough air/fuel mixture entering the 125cc engine, but it starts first time and you can rev it to full throttle no problem. I can't ride it yet as still rebuilding the scooter, so no road test yet to see how it performs. I am a self taught mechanic and have worked on vehicles from scooters/mopeds up to trucks of 44 tonnes This problem has baffled me so hope you guys can maybe give some advice as to what you think might be the problem. Once I can test ride it I will report back here to let you all know my findings using the 50cc carb
yes using the original airbox with both carbs. the jets are the ones which was in it when purchased The pilot jet for the 50cc is a 34 and the 125cc is 35 I do have a 38 I could even try
I have done this twice before but all looked OK I did however take it apart after turning it upside down and found that the float could not be heard moving inside. I started by straightening the float out and then bending it about how I thought it should be and could hear it moving when turned upside down. With a piece of pipe on the fuel inlet I could hear when blowing air getting in, and as I turned it upside down still blowing the air stopped, so back on the engine and bingo it started and revved up. I think as no history of the engine it had been mucked around and was not set right. I also found you had to keep the carb upside down to fit carb bottom as the float would stick if upright Thank you everyone for your thoughts on this matter but now resolved
Well ran with 50cc carb but still wanted to use 125cc carb Great news Finally got it sorted After a lot of stripping carb many times found that float was hitting float bowl and holding valve open causing flooding After some mucking around decided to start a fresh so bent tag on float straight and then tried different settings and got it right runs great now and nice to be able to ride now This 125cc engine is in a Yamaha Neos 2T 50cc now after a mod on engine mounting and has a rear disc brake fitted now.
