I have a Thunder Tiger .42 that belongs to our club. It is old and has been through a lot - when I got it the carb mounting lugs were broken off and it was heavily varnished. I took it apart and cleaned it using the24 hours in antifreeze and a crock pot trick. Looks like new! I tried to get a new carb from Ace Hobby through my LHS - no joy. I finally got one direct from Ace after a lot of negotiating, but it too was used. I replaced all gaskets.
Now to the problem. I ran the engine up today and found it has a great idle. It starts very easily. However, there is virtually no needle valve control - I can back it out all the way with very little effect. If screwed in beyond less than four turns out, it quits at half throttle or more. I can feel a fine spray of raw fuel on my hand when it is in back of the engine. I am running muffler pressure, and Byron's 15%.
When it does run at full throttle, it cannot four cycle - it just two cycles with a lot of power and little smoke. After a short period it clearly slows and then stops - I think this is because it is so lean that the engine is getting too hot to run.
Everything points to a lean condition at full throttle. Air is getting in somewhere besides the thrttle barrel I guess. Is it possible that the crankshaft seal is shot, and thus is sucking air in there? Why is the needle valve useless? Any thoughts would be appreciated - it looks so good, I really do not want to abandon it.