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Old Jul 12, 2015, 11:17 AM
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Spaceage Johnny
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United States, FL, Clearwater
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Brand new engine runs fine on starting table but quits when in air

I have a brand new ASP 25 (Hobby King cheepO). New Hayes fuel tank. Engine runs at WOT and at idle while on the starting bench at my flying field. I can let it run thru a whole tank on the bench with no problem. It will transition from idle to WOT fast or slowly. Sounds good - acts good on the ground.
When I get it up in the air I can get 1 or 2 laps around the field then engine sound changes to a lower pitch and then quits soon after. I have tried WOT, 1/2 throttle,
1/4 throttle. no luck, same result.
Also, have had several guys that I know who are pretty experienced, tune it, with same results.
Any ideas?
Thanks,
John
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Old Jul 12, 2015, 11:45 AM
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The clunk in the tank should not be right at the back of the tank. It should be ahead maybe 3/8". Otherwise, I don't know, might need more pressure from the muffler, or just a bit richer? More breakin.
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Old Jul 12, 2015, 11:49 AM
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clunk is about 1/4" with free movement. how would you get more pressure?
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Last edited by John M..; Jul 12, 2015 at 11:50 AM. Reason: typo
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Old Jul 12, 2015, 12:31 PM
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Are you using a tachometer to set the high speed needle? If so, what RPM are you getting and setting it to? How many tanks of fuel do you have through it on the bench? It sounds to me like it is leaning out once in the air indicating you have it too lean on the ground.
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Old Jul 12, 2015, 12:47 PM
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If there is a cowl on the plane, try flying with the cowling removed and see if that changes anything. If the engine isn't cowled, it's likely just too lean. New engines should be ran a bit richer for awhile until they break-in good. Some engines take awhile to break-in and until this happens, they will run a little hotter since they're often a bit tight when new.
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Old Jul 12, 2015, 01:59 PM
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I've only had 1 tank - 6oz. thru it. no cowl and I don't have a tach. I'm going to set rich, or more rich and fly it this evening after the wind dies, which should be around 7pm eastern - it is way to hot n windy right now.
thanks for your replies.
John
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Old Jul 12, 2015, 02:05 PM
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One tank? How is that enough to judge whether or not it runs right on the bench? It hasn't even begun to be broken in yet. What prop size are you running? Are you following the instructions for breaking the engine in?

http://media.hobbypeople.net/manual/210630.pdf
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Old Jul 12, 2015, 05:24 PM
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Quote:
Originally Posted by John M.. View Post
clunk is about 1/4" with free movement. how would you get more pressure?
The hole in the pressure fitting could be on the small side, and the outlet hole of the pipe can be reduced. I think it is just too lean and not broken in yet. I have had to run motors on backplate pressure when the carb hole is too big for good suction. A regulator may be needed with a throttle.
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Old Jul 13, 2015, 04:47 AM
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Spaceage Johnny
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yesterday evening I set her way rich - more than 4 turns out, it flew pretty good.
Thank for all your replies
John
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