Q-500 Racing Discuss AMA 428, AMA 424, and any other variants of Quickie 500 racing

TT GP 42 Engine Leaking and compression decline

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Old 09-01-2008, 12:44 PM
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cmoreno.rj
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Default TT GP 42 Engine Leaking and compression decline

Hi everyone,

I was flying my Viper 500 with TT 42 (bearing free according to our regulations) this weekend and after some laps, it became very slow. After I check, I could see that there was some fuel leaking from the above of the engine head. I have dismounted , saw that inside the oil was black like burned oil. After I tight the screws again I opened up a little the high speed needle but it keeps leaking and losing compression after 6 laps....

Does anyone can help on that subject ? What do you recommend? Of course the easiest answer is : Buy another one !!! but I have hope that anyone can help me out !

Thanks and rgds !

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Old 09-01-2008, 07:29 PM
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Duane-RCU
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Default RE: TT GP 42 Engine Leaking and compression decline

We also used these engines on our club planes. They do not like to run hot, they lose compression very fast. Do the crock pot (anti-freeze) cleaning method to get rid of any gunk that has baked on. After that, do not spend alot of time leaning it out on the ground, it will get hot fast again. If it is still fresh, it may take some time to break-in properly before it will handle max rpm. With a 10x6 MA prop, most get around 13,000 on the ground some up around 13,300 (stock muffler) If you use a 9" prop, you might get more. But this is a sport set up, and won't do big numbers. OS 8 plug works good too, 10-15% nitro max.
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Old 09-01-2008, 10:53 PM
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Default RE: TT GP 42 Engine Leaking and compression decline

the black burn on the piston means its running to lean, open the needle
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Old 09-02-2008, 12:03 AM
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Default RE: TT GP 42 Engine Leaking and compression decline

try a new head shim plus torque the head down evenly and tight.
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