QT50 Carb Overflow

Trying to get my 1979 QT50 up and running. One of the parts I bought was a new carb - was only $20 and was easier and cheaper than buying parts and rebuilding the old one.

Got everything installed last night and tried to start it but couldn't get it to run. I think it has something to do with the ignition switch but I'm here about a different issue.

The overflow tube on the carb is constantly dripping. Normally that means the bowl is overfilling or the float is stuck but how is this happening with a new carb?

I know gas is getting into the cylinder head because I checked the spark plug for spark (it did) and it was wet with oil and gas.

I also have no idea what 1 screw does other than let more or less gas out of the overflow tube. It's the flathead screw down by the overflow tube. I took it all the way out and it's like a cone with a spring on it.

I had to swap out the top plate where the throttle and choke lines come in but both seem to be working fine with the old top plate.

Any thoughts?

Below is a pic of the model carb I bought.

Re: QT50 Carb Overflow

Luke Vidacovich /

Just did a little reading and I have 2 ideas - make the end of the carb overflow tube above the float and put the screw by the overflow all the way in.

Re: QT50 Carb Overflow

if you have the stock carb i would use that and just clean the jets, very easy.. I just picked up a parts qt50 that came with that same carb... doesnt look very quality.

pictured above

gold screw is idle, silver screw to the right is air fuel mix and bottom screw should be all the way screwed in... thats the carb drain

Re: QT50 Carb Overflow

Luke Vidacovich /

I'll give it a shot tonight with the new carb and if I can't get it running I'll try the old one. I have carb cleaner and I can use the parts I needed (the throttle and choke stuff) from the new carb.

Re: QT50 Carb Overflow

Jack Rutherford /
qt50carb.png

If fuel is leaking out the drain hose then the drain screw is not tightened sufficiently. (edited)

Re: QT50 Carb Overflow

Jack Rutherford /

or the fuel isn't coming from the drain hose and maybe you have a bad float bowl gasket, or that gasket is misaligned or your float bowl screws aren't tight enough.

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