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HomeRC & Power✈️Aircraft🚁HelicopterEngines Plugs Mufflers Fuel › TT39 Pro-H Woes.....
05-25-2007 06:54 PM  13 years ago
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SilverBullet

rrApprentice

Bentonville, AR USA

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TT39 Pro-H Woes.....
I know this has been covered, but I have to vent.

I bought a used Raptor 30V2 that came with a TT39. I put a new gasket kit on the engine, new plug (OS #8), new fuel lines, and new clunk lines. I added a header tank and TT High performance muffler. For the life of me, I can not tune this engine. In order for me to have the low needle low enough that I can maintain an idle at 18% throttle, the engine gets way too hot. I have the main at 2 3/4, and the low needle at 2 1/2. At that setting, I have to keep my throttle at 31% just to maintain an idle, and the muffler is dripping and spitting fuel. If I lower the main to 2, the engine gets a high pitch whine at 50% throttle and above. After about 20 seconds of hovering, you can't keep your finger on the backplate for more than a second. In order to maintain an idle, I have to have the low at about 1.5 turns and same thing...sounds like the engine is overspeeding and it gets too hot to touch the backplate. I even did the needle mod.

Any suggestions?
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05-25-2007 07:57 PM  13 years ago
w8qz

rrVeteran

Grand Rapids, MI - USA

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I assume you've checked this, but I'll ask the question anyway Is your clutch dragging / not releasing? That puts a heavy load on an engine at idle. I've also learned, the hard way, that a TT clutch can have a hairline crack in it that is very difficult to see. Polishing the outside with fine sandpaper - at the 'flex' area - should reveal a crack, if there is one. I'm surprised at how much more load a plain old propellor puts on an engine, compared to a properly releasing clutch."The helicopter is much easier to design than the aeroplane, but is worthless when done. W. Wright"
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05-25-2007 09:20 PM  13 years ago
SilverBullet

rrApprentice

Bentonville, AR USA

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I pulled the engine today and the clutch looks good. What I did notice is that the throttle cylinder has some side to side play where it goes in the carb (lateral as compared to heli body). I also noticed that with the throttle arm fully closed, you can rotate quite some distance before it opens to let air into the carb (could explain why it won't idle until at 30%.

I am running CP 30% fuel. Considering this is a used engine and I don't know the history of it, I elected to purchase a new TT39 today. I know, I know, I should have just upgraded to the OS50. I just don't think my skills are ready yet, and I am happy just puttering around in figure 8's with my 30. Eventually I want to go scale with the MD530. Helikraft had the TT39 for $84 ($30 cheaper than anywhere else). I figure I'll give the new engine a shot and maybe work on rebuilding the old one (when I am not flying).
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05-26-2007 01:54 AM  13 years ago
baby_zyklon

rrElite Veteran

Singapore

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sounds like you have the rich idle, lean mid range symtom. Check out the low needle mod.
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05-26-2007 12:43 PM  13 years ago
Busher

rrKey Veteran

Manchester, England

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Mine had to be set up very rich on the idle needle, so rich in fact it hardly maintained its idle, I got around this by using about 25% idle setting on the tranny. However even at this setting the heli would not really idle for more than 30 sec, I then had the main needle set rich and worked the needle in from there. I found that once the engine had become warm the idle improved and all was well, it just had to clear the engine of the excess oil from idling. The engine is quite powerful and will serve you well, but I have just got an OS37 szh and difference in handling is noticable, and there is also a difference in power, I am sold on the OS but I still maintain that the tt39 is a good engine for the money.
One other problem I had was a worn rear bearing, and it showed up as vibration and overheating of the engine was very evident, check your bearings and replace if necessary.

Good luck

Busher
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06-20-2007 04:00 AM  13 years ago
SilverBullet

rrApprentice

Bentonville, AR USA

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Solved my issue....got rid of the used TT39 and bought a brand new one. Fired it up today on stock settings to let it idle, and it purred like a kitten. Had the throttle at 18% with no problems. I can only imagine how what it will be like after I break it in.
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