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My repaired OS engine won't stop running .

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Old 03-20-2006, 09:18 AM
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Hobie
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Default My repaired OS engine won't stop running .



Howdy all .
At the end of last flying season I broke the crankcase on my OS .46AX in an inverted dumb thumb crash [:@] . I finally got around to putting a new crankcase on it and fired it up yesterday . It started easy ran good I tuned it back up sounded good but it won't quite running with the carb all the way closed [] .Any ideas on what could cause this ? I am assuming it must still be getting air somehow . Any suggestions on what to look for ? Thanks in advance . I have a Sig 4* .40 ordered from Tower for my birthday and I want to make sure this engine is good before putting it on a new plane . Thanks .

Bruce
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Old 03-20-2006, 09:32 AM
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AllTheGoodNamesAreTaken
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Default RE: My repaired OS engine won't stop running .

One method I've used in the past to find air leaks is to use WD-40. With the engine running and the throttle closed, very carefully spray (using the little red hose) a very small amount around the carb base. The WD-40 will be sucked up into the engine and the engine will quit running. WD-40 wont hurt your engine either. If you're real careful, you can pin point the air leak this way. Just don't cut your fingers off with the spinning prop.
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Old 03-20-2006, 09:41 AM
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fokker20planes
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Default RE: My repaired OS engine won't stop running .

Everything Clarence Lee has said in his past articles says that it is getting air from somewhere so you are correct. Try where the carb attaches to case. Is the O-ring still there? Try putting a piece of fuel tubing over the needle valve. I wish I could remember how Clarence said you could submerge the engine in water and by pressuring it you find where air is escaping. If I find an article on this I will post it.
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Old 03-20-2006, 09:41 AM
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Default RE: My repaired OS engine won't stop running .

I've used an unlit propane torch also to find an air leak. The engine must be at idle so the added fuel will cause an rpm rise. This was on a gas engine and probably would not have much effect on a glow engine. I posted before the morning coffee had kicked in.
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Old 03-20-2006, 09:42 AM
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Default RE: My repaired OS engine won't stop running .

I also agree, this sounds allot like an air leak. Check around the carb base, the crankcase back plate, the front bearing seal and anywhere else there is a seal that could leak.

If you re-used any seals from the damage then most likely there is your air leak
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Old 03-20-2006, 06:25 PM
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Hobie
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Default RE: My repaired OS engine won't stop running .

Thanks guys the carb seal is bad I ordered one from my LHS today . Hopefully that will fix it and that is the only air leak .
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Old 03-20-2006, 06:50 PM
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Default RE: My repaired OS engine won't stop running .

I spread a little goopy around the base of the carb body where it fits on the crankcase, just before I push the carb into the crankcase. This seals that leak area.
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