bad running GY6 150
 

Fired up the buggy first time today, It would not run at idle but plenty of power when revved/driven. Stripped the carb soaked in carb cleaner and cleaned all the jets, It would then not run at all maybe fire if I played with the throttle, So stripped again found nothing wrong put it back on, now it runs, not on idle but it runs. Now when I drive it accelerates well then shuts off for a few seconds then off it goes again accelerates up then the same thing. So the question is what have I screwed up. New air filter, float set at 18mm no vacuum leaks good spark and compression of 138

Your compression is a little on the low side. Did you try a bigger pilot jet?

if you're 100% the carb and especially the pilot jet is truly clean, check fuel tank and petcock. the gel from ethanol fuel that's broken down can float around then suck in and clog the tank filter--- then float away again. have also dealt with several petcocks that the internal seals have degraded and caused the same kind of intermittent issue.

I would have thought enough compression, it runs fine just hits a certain rpm and stops, like hitting a switch, no spluttering or misfire it just stops then a few seconds later off it goes again, not tried re-jetting just thought get it running standard first, new carb is here so will give that a go

Got this bad boy today pre set for a 150, so hopefully it will eliminate any car issues. Good point on the tap I will pull it before replacing carb, I changed the filter and never thought about the one in the tank thanks for that

definitely drain the tank and inspect the inside. nothing worse that putting a new carb on and chasing the same issue all over again. been there, done that.

Drained the tank, Thanks for the tip, it looks like someone had resprayed the tank without masking there was bits of peeled paint, when it was empty they stuck to the side but with fuel in they were floating around. So i cut the top off and scrubbed it out, (had to do this as cannot get spares easily here in Poland) going to re-weld and paint today. With a makeshift tank the new carb has sorted the idle problem. So now on with the brakes and lights.

sounds like you found the issue. you might want to see if you can find a radiator pressure test setup so you can leak test the tank after welding it.