Skribnod

Hi I have a St90 that wont run for over 4 minutes without bogging down and overheating (so hot it spit sizzles on engine case). I recently put a new carb on it from towers and have to have the low speed needle 7 1/2 turns out to get it to run at all !! I run it uncowled on the ground and high speed needle rich. It dies in flight or on the ground without the cowl on. Does anyone know why this might be happening? Tried every needle setting possible. It is a older "S" model with the new model carb (thats all towers offers). I checked for fuel line obstructions and it seems like it is getting enough fuel but just wont quit overheating. Fuel I am useing is Wildcat 15% nitro 80/20 castor blend 16%. Thanks

Skribnod

BTW I tried a 13x8 and a 14x6 prop.......both of which manuf. specifies.

Superscott

Hey, My wife has a duratrax Thunder quake with a torq .21 engine well the stupid motor would not even get through half tank without over heating. Wrote the company and they said that the piston and sleve could have got dirt on it and scored it. Don't know if that helps?

FLYBOY

My Feedback: (11)

Are you getting bubbles in the fuel system? Sounds to me like something is not right there. You shouldn't be 7 turns open on any needle. It isn't getting fuel for some reason!

DBCherry

My Feedback: (4)

Is the tank set way below the spray bar in the carb? Are you sure the pressure line or muffler nipple aren't blocked? A pin hole in a fuel line?

I'd try to find the problem before running it that way for long. A couple "sizzling" hot lean runs could ruin it.
Dennis-

Montague

You might try a fuel with a higher oil content. 16% isn't bad, but I've had engines that had heat problems until I went to a different fuel with differnet oil package (more oil, and different blend)

Try lower nitro as well, ST engines tend to have pretty high compression, and often like lower nitro fuels.

Most likely, however, is a problem in your fuel system. I agree with Dennis and Flyboy, it sounds like the engine isn't pulling fuel from the tank like it should, which could cause the problems you are having.

Skribnod

I have ran the engine on a test stand also with the same results. The pressure nipple is not restricted and no air bubbles present int eh fule line. Also tried a different muffler (had a pitts on it) and different prop sizes. I think the carb is screwed up from towers. I checked the spray bar and it is unobstructed also.

FLYBOY

My Feedback: (11)

Have you tried blowing out the carb with fuel? Might have something stuck in it somewhere. Doesn't take much. How does the engine run with a different carb? That might be something to try. That hot is not good. Have you got a temp sensor to see what it is getting to?

Montague

I'd say try another fuel for sure then. Espeically if your test stand setup used a different tank than what was in the plane. Try something with 5-10% nitro and 18-20% oil.

MinnFlyer

My Feedback: (4)

Skribnod, It is against RCU policy to post the same question in more than one forum at a time. Since this is also posted in the Engines Forum (which is probably a better place for it), I'm going to close this one.