Dragonfly .049 Fuel Delivery Issues

Iceberg Sat Feb 16, 2019 3:26 am

I have a black dragonfly with extended tank that for all intents looks practically new. However it really struggles to keep consistent fuel delivery. It runs and then stops. I put hose over the needle to stop leaks etc. I put spring in the clunker pick up tube to improve draw, However it is hard to keep it running with out speeding up and slowing down. Any suggestions to stabilize the fuel delivery? I can see why Cox only made them for a couple years. Pretty poor tank design. When I fuel it up it might even flood really bad before finally starting then doing its up and down rpm then stalling. Only to start again and repeat the same nonsense.

Looking for comments.

Thanks
Iceberg

Levent Suberk Sat Feb 16, 2019 3:40 am

Clunk hole is clean? Gaskets are new? Perhaps it is an air leakage problem.

Iceberg Sat Feb 16, 2019 3:54 am

Well I did several tear downs last week. Those dragonflies are super tough to fix to anything as the screw fixings are So long. Maybe there is a plug in the clunker. I did blow out with compressor. However will check again. Thanks
Iceberg

Mudhen Sat Feb 16, 2019 10:19 am

Iceberg Sat Feb 16, 2019 4:59 pm

Thanks Mudhen
I'll look when I get to the shop later. I hope it's not cracked. If so what to do? I don't have replacement tank. But the condition of the motor is really good almost like new.

Thanks!
Iceberg

ticomareado Sat Feb 16, 2019 7:51 pm

There's a reason those plastic tanked Bees didn't have a long production lives.

Dave P. Sat Feb 16, 2019 9:21 pm

It might also be the clunk tube has a pin hole. It also needs to be super flexible, regular silcone fuel line isn't flexible enough. I'm pretty sure I saw that Cox International and/or EX Engines has replacement tubes.

ticomareado Sun Feb 17, 2019 9:54 am

I have two with broken plastic nipples. That's what turned me of to all those plastic tankers.

Iceberg Tue Feb 19, 2019 3:33 am

So tore down the engine. Found there was an air leak up around the brass nipple the that NV threads into. I pulled it out and pressed it in with a ring of super glue around the top. The motor leak is fixed. Motor starts and runs very strong.

Now another issue that is needing to be fixed.

The needle (brass) I installed using two sizes of nitro tube around to stop it from leaking. However while running now it is screaming pretty good. However the vibration is enough that the needle vibrates enough to keep putting off the proper setting. If i hold it with my fingers it will hold steady but when I let go of the needle the motor is not steady any more. If the needle was shorter it would be better. It is vibrating about 1/16" back and forth +-. Or should I put the spring back on? I thought the hose was the cat's meow but maybe not for the longer brass needle?? Maybe the spring would hold it steady?

Thanks
Iceberg

Levent Suberk Tue Feb 19, 2019 4:23 am

Can you stop the vibrating a little by using thicker material (or metal sheet) for engine mount? I think that spring is better than fuel tubing for this problem. Silicone fuel line is slippery with fuel.

Iceberg Tue Feb 19, 2019 6:03 pm

I put a Medallion spring on it. I'll try tonight after work. The engine mount I used 1/8" aluminum screwed to a 2x2. I thought should be strong? Works awesome for all my other motors but this extended dragon is a little bit of a pain I agree! I'll see if there spring makes the difference. Thanks Ice

roddie Tue Feb 19, 2019 7:18 pm

Hi Iceberg, Good to know that you got the first problem worked-out.

Regarding the needle-movement from vibration.. You "can" stabilize the needle-shaft by using a simple "hair-pin" (Bobby-pin) and two short pieces of "silicone" fuel-tubing. The "pin/clip" is then secured to the engine-mount with a small wood-screw and flat-washer.

These photos might help you to work-out a solution to fit your application..