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Cox .049 Dragonfly - 2/26/2003 10:10 PM   
soarrich



Posts: 4397
Score: 136
Joined: 2/1/2002
Last Login: 5/21/2013
From: Middletown, NJ, USA
Status: offline 		I have a Dragonfly engine that I'm having trouble with. Every time I get it to run, 2 seconds, it develops an air leak between the crankcase and the tank. Is this a common fault? I tried retighting it to no avail, so I put some Hi-temp RTV on it in hopes that will seal it, I'll test this later today to see if it worked.

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Cox .049 Dragonfly - 2/27/2003 12:17 AM   
DICKEYBIRD



Posts: 2728
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Joined: 4/9/2002
Last Login: 5/18/2013
From: Collierville, TN, USA
Status: offline 		The Dragonfly was (I thought) the perfect engine when they first came out. It may just be me and some kind of bad Ju-Ju but I've had a lot of trouble getting them to run steadily.

If you're having trouble with case/tank leakage, did you flatten the rear of the case with some 600 wet/dry paper on a piece of glass to remove the lumps around the tapped holes? This has to be a standard procedure on all reedies to get them to seal. I assume you're using the paper gasket as well? It seems like they stopped using the paper gaskets later on but I think they're mandatory.

Also, I think the venturi opening is too large for consistent running on the D/Fly. Fellow Cox-a-holic buddy Lester Goldsmith came up with a cure that seems to smooth 'em out. He stuffs a short length of medium (I think) silicone tubing down into the venturi opening which reduces the dia. enough to really improve suction. I've had a couple of 'em with a good TD piston/cyl. installed that would really scream at enough revs to properly use that big venturi opening but they were still very touchy. I gave up and switched back to detuned TD's for my sport flyers.

HTH!

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Cox .049 Dragonfly - 2/27/2003 1:40 AM   
soarrich



Posts: 4397
Score: 136
Joined: 2/1/2002
Last Login: 5/21/2013
From: Middletown, NJ, USA
Status: offline 		Dickeybird
Thanks for the info. I already used the RTV, but if that doesn't fix it I'll do the 600 paper thing.

I modified the throttle muffler, I'm going to run it bare, then with a stock muffler, then my modified muffler. I may be able to barrow a db meter to get sound readings to go with my tack readings. I still have to turn a exhaust outlet for my muffler, I'm hoping the flexible body will help quiet down. Any idea on how big the exhaust outlet should be?

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RE: Cox .049 Dragonfly - 5/19/2012 12:51 PM   
loverofyahshua


 

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Last Login: 7/22/2012
From: Fresno, CA, USA
Status: offline 		After countless hours of Cox Drangonfly 049 R&R, I discovered a CRACK, in the Suction nipple Area. No way the engine could pull any nitro fuel. Then I switched to WHITE Dragonfly 049 style. Then, I discovered a leaky rubber seal on the needle valve. Now, at least it runs continuouly. I hope to get the muffler throttle to work, and then a diesel conversion. After that, I will use a diesel with a carburetor. Hope for the best.

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