Misanthro

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I've got one of thses engines and it looks nice, but I'm having a hard time tuning it right. Can someone tell me the start positions for all the needles (and maybe there locations. I know where the high end is..and I think I've got the low end, but I hear theres a mid range too?). Unfortunatly I started playing with it before I knew alot about the engines and had it screaming on it's first tank. I hope I didn't damage it too much.

THE TAILBACKER

I am running one of these on a .40 size WM P-51. Frankly, tuning it up is the same. One thing here is be careful on your prop size. If you run to large a prop it will run great on tune up but goes down hard on take off roll.
Sounds like you get the general tuning idea so i am going to bypass all that. There are ways to check what you have adjusted and they do work.
Start your engine up and get it tuned the way you think is fair to okay. Lets check you low end setting. While the engine is running at an idle, disconnect the fuel line from the nipple, if the rpm increases before the engine dies, the low end is to rich, therefore, close it a bit. If the engine rpm just goes down and quits, your to lean, therefore open the low end a bit. Now a bit maybe and 1/8 turn at most.
Now what I do is look for a "slight" increase.

What you need to do is purposely get it rich and to lean to see the difference and go for the happy medium.
Once you got that down. Do the high end.
Get the engine rich and close the needle up. once you get that peak rpm, do a quick pinch test on the fuel line that connects to the nipple. This is a quick pinch and release while the engine is at full speed. If the engine wants to or does quit, it is to lean. Some people look for a a quick increase in rpm, then back to normal. Me, I go for no change. With these back up checks you can tune an engine perfectly.

www.geocities.com/slewfoot42/mlh

Misanthro

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Thanks alot for the info. I'll try that tomorrow. Just to make sure...you say close it to lean it and open it to richen it on the low end. Is that right? Because most low end needles are the opposite of the high end (out for lean, in for rich).

THE TAILBACKER

You just solved your problem------Most 99.9% engine low end needles close for leaning and open for rich just as the high end!! Later.

Misanthro

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Oh...one more thing. On the issue of props. I've got the engine on a Piper Cub 90" wingspan. Right now I'm running a 12x6. What do you think?

THE TAILBACKER

Sounds good. Did you catch what I said about the Low end??

Misanthro

My Feedback: (1)

Yup. Close for lean, open for rich. Thanks.

Macgyver

You should try A bigger prop on A 90 like A 13/6,13/8,14/6,I use 12/6 on 60 size engines.Take care-Mac

vertigo

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On that large scale cub you need the 14x6 prop.

Happy flying

Misanthro

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I've got a 14x6 laying around but I didn't want to over prop it. Thanks guys.

Vince

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A 14 x 6 is perfect for the ST90.

Vince

uciflylow

I run the APC 12x6 on a MDS 58, 13x6 on the Super Tigre G75 and plan to use the 14X6 on the ST G90 I have for a Midwest citabria.

Ed

You seem to be determined to burn that thing up.

USE THE 14 X 6 ! ! !

Vince

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Yep, then he will be bad mouthing Super Tigre's.

Vince

Misanthro

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Finally got the ST running smooth. Thanks alot Tailbacker. I took the engine apart tonight to clean it and realized how bad I actually messed that thing up in the time I've had it. The piston and the sleeve is charred from being run hot. All I can say is I definatly won't be bad mouthing Super Tigres. They sure can take one hell of a beating and keep running great.

THE TAILBACKER

You bet!