Hello Bax:

I have a 61FX that has run great up to last weekend, when it started acting up.
I run the following set-up:

Fuel is 80% methanol and 20% Castor oil mix.
Tuned pipe with 12x8 APC prop which turns at aprox. 12000 rpm

Last weekend it started as normal, idled perfectly but the high end was not stable. The engine acts like its really rich (when pinching the fuel line the rpms immediately go up).
I have to start closing the high speed needle until its less than 1 turn open, in order to reach the usual rpm range. By having the needle in this position the engine will overheat. If I return to the normal setting of between 1,5 and 2 turns the engine only delivers about 9000 rpms and if the engine is left to idle for some time (10-20 seconds) it will die when you throttle up.
I have tried a new glow plug, different fuel, checked the fuel tank for leaks, changed fuel lines but with no luck. I did not make any changes prior to having the problem.
I would really appreciate if you can help me find the source of the problem.

Thanks in advance,

Al