Ok guys, I have a ST 40. I just mounted it on a new plane and took it out. it ran and flew fine for about 1/4 of a tank and then it dead sticked. when I tried to restart it, it ran and then died like it was out of gas. it had plenty, the clunk is down and fine, it looked like there was a lot of air bubbles moveing through the line though. Each time I started the engine it would start and when idled up it would cut out and die if I didn't pull back on the throttle. Do you think it has to much air in the tank/lines or maybe something else. If it is an air problem how do I fix it? thanks for any info you have.

My first two guesses are:

1) A pin-hole or split in the line going to the clunk
2) The fuel is foaming

You said that it died after about 1/4 tank. Did you refill the tank and see if it would run ok??

Either way, your problem is definitely the air in the fuel line. You have an air leak someplace. I asked if you refilled the tank to see if it would run fine about 1/4 tank. If it does and then dies when it gets down to 1/4 then more than likely you have a pinhole in fuel pickup line inside of the tank.

If you have problems no matter where the fuel level is then you have a leak elsewhere. First check the stopper in thefuel tank. Check to ensure that it is tight on the fuel tank. Also check your fuel line to the carb for pinhole leaks.

Ken

thanks guys. I'll pull it apart and put all new line in the tank, and to the engine..

Sounds like the best plan.
A hole in the line inside the tank, runs good until the fuel gets down to where the hole is.

Runs out of fuel and dies after 1/4 tank?

Did ya accidentally hook up the carb line to your vent tube in the tank?

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