I have a thundertigre 1.20 two stroke engine. Never had any trouble with it, but I recently put it in a new plane (inverted now....) and I dont know if it is when I inverted it or when I put in a new plug that it started to be very difficult to start. I never noticed what plug was in it or which one I replaced it with.

But, once it is running, runs perfect. Good idle, good transition etc....

It seems like I have to prime it by holding my finger over the muffler exhaust for a second or two....because I dont get a spark...but if I hold it there a little too much, it wants to vapor lock. I completely replaced the remote glow starter, and I am getting a green light on multiple glow drivers....

Any idea's, and what plug should I run in it? I have been flying rc for 20yrs, never too late to learn something new.

Thanks in advance,
Patrick

you might want to check your tank location. now that your engine is inverted, the carb may be more than 3/4" below the tank center line.. which can make fuel gravity feed really quickly once a siphon is started (when you prime the engine)

The trick is in perfecting a new priming technique because with an inverted engine the carb is also inverted (obviously ) so fuel tends to just dribble out instead of running down into the crankcase. But spinning it over with the starter with your finger blocking the exhaust can force too much fuel through and flood it. This of course is bad news for an inverted engine, first because it drowns the plug but mainly because you can get a hydraulic lock.
When you get the technique right you'll find it'll start just as easily as an upright engine.

actually one technique is flipping the plane upside down in a cradle and starting it like that. lol..

but a 1.20 sized plane might be a lil too big for that.

Thanks guys,
I changed to an o.s. #8 plug (hotter), seems to really help.

Thanks for the advice.