Small Engine Troubleshooting Problems? Ask a Mechanic Now.
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Does this engine have a fuel pump on it? Have you check fuel level in the bowl when it dies to see if there is even any fuel in the bowl?
Approximately how long will it run at full throttle before it dies? Have you checked the fuel tank vent to make sure that you are not creating a vacuum inside the fuel tank that would cause fuel to not flow fast enough to keep the engine running?
It just sounds like you have a fuel restriction but based on everything that you say that you have already done I don't see how that could be.
Can you put a spark tester in line between the plug wire and spark plug and see what the spark is doing while the engine is running? It is possible that the spark is not advancing properly at higher throttle, maybe a weak ignition coil.
To your knowledge has the engine been taken apart recently and put back together, a chance that the internal timing marks were not lined back up correctly when installing or putting back together?
If it were one tooth off on internal timing it would still start but at higher speeds the valves would be off time just enough that they would not close fast enough. At slow speeds or idle it isn't as much of a problem.
I am going to opt out of your question which will allow for one of the other experts here to weigh in on your question and maybe provided some other ideas for you.
Have you tried to run it out of a raised fuel container? Sounds like the fuel is not keeping up with the needed supply.
Exhaust open? Engine has to loose spark or fuel. with it starting right back up, would seem to be fuel! That means the restriction is in the fuel supply or the needle valve and float.
exhaust will not affect compression!
If anything, it will raise the compression!
If exhaust does not get out ,gas can't get in.
That is not the point, the exhaust port would be plugged with carbon, not a bad valve!
Or the exhaust pipe.
OK, I cant add anything, I will opt out. sorry.