G'day

It is just possible that the tank is too tall (or too low) and so as the flight progresses, the mixture becomes leaner and eventually the engine stops.

There is an easy way to find out.

1. Fill the tank to about 1/4. Start the engine and tune it for flight.

2. Now fill the tank. Start the engine again AT THE SAME TUNE. Is it running much the same as before or is running really rich?

If it is running as it was at 1/4 tank, then the tank is not the problem. If it is slobbering rich then you have a problem.

One possible cure is to use a second clunk in the tank for the vent line (which goes to the muffler) so that the two clunks are separated by about 3/8 inch and they are tied together by something like heat shrink or cable ties (loosely). This setup is called a Uniflow tank and gives a better top to bottom engine run.

There is also the extremely rare possibility that the muffler pressure connection is blocked. This would be unusual with a new engine but I had one pressure fitting that had not been drilled properly.

After writing the above, I saw your comment about a "burnt up engine". If it is "burnt up" then it has been running hot. Hot running means that either it is not getting sufficient cooling or it is being run lean or it was not ready to fly and needed more running. I think the most likely is that it was running lean possibly because of the tank problem I outlined. The engine is probably still OK. It just needs the right amount of fuel throughout its flight.

Can you show us the setup? How high is the engine relative to the tank? What fuel are you using? Prop? Plug? Muffler? All these things can affect how it runs.