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Help with a Babe Bee --loses power, slowly dies

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Help with a Babe Bee --loses power, slowly dies Empty Help with a Babe Bee --loses power, slowly dies

Post  flyjsh on Sun Apr 28, 2013 3:50 pm

Howdy all,

I need help.... and so does my engine.

I have a new Babe Bee, and I cannot for the life of me get it to run smoothly or for more than 30 seconds. Break in consisted of two tanks run so rich it was spitting raw fuel everywhere. The next five or six tanks, I ran it a bit leaner until it was near peak. It never ran smoothly, but I assumed it was because it was new. So the last two day I've tried it the first start attempt goes fairly smoothly (fires up quickly), then I lean it to just rich of peak. But after a few seconds, it starts to lose power and runs rough. It sounds like it is getting progressively richer until it quits. Each successive attempt, it gets harder to start and runs worse. One thing that concerns me is the hotter it gets, the less compression it has. It doesn't have too much to begin with (it just doesn't have the pop or snap the my Sure Start has). Suggestions????


(fuel is 15% nitro.. I know, should be higher but it was the best LHS had, and it runs my Sure Start just fine)

Thanks,
John
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Post  RknRusty on Sun Apr 28, 2013 4:46 pm

Is this a new one from Cox International or Ex Model Engines? With 15% nitro you only need one head gasket. Take the head and make sure the seat is flat. Put some 600 grit paper on a piece of glass and sand the mating surface of the head so as to insure that it evenly compresses the gasket. Use a balanced 5" or 5-1/4" prop and let it rip at full peak and see if it straightens itself out. If not there might be an air leak between the crankcase and tank. Lots of other things could cause it, but with that and report back. Dry the whole engine off before you fill it with fuel, then look to see if it gets wet under the tank at the case with fuel sitting in it. You could try another head too.

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Post  pkrankow on Sun Apr 28, 2013 5:03 pm

15% nitro should run fine (less nitro = more touchy to adjust the needle).

Sagging could mean an air leak, or it could mean a dirty reed, or a dying/dirty glow head.

If the engine performs as expected if you leave the glow driver hooked up the glow head/plug is at fault.

If the intake is accessible you can try flooding though the intake with fuel to try cleaning the reed without disassembling. If it still sags after flushing the reed seat you will still need to take the engine apart and clean it.

Close the needle gently and pressure test the tank with some fuel in it to test for air leaks. You can do this on the airplane. If you have air leaks you will need to take the engine apart, and reseal it. Consider using an aluminum safe (anaerobic, or labeled for aluminum) sealant.

Phil
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Post  flyjsh on Sun Apr 28, 2013 6:19 pm

It's from Cox International.

There is NO head gasket at all (that is how it came). Is one required or can a good seal be made without a gasket? How tight should the head be? Is it like a spark plug: snug plus an 1/8 of a turn? I haven't run a whole tank with the glow driver hooked up. I'll try that next, and I'll swap out the head with a known good head as well as a double check. I'll also look for leaks. If I put a fuel line on the filler and blow air in (tank full), would that be good enough to find the leak?

Another question, this one regarding fueling. All the Bees I had as a kid had two fillers on the backplate (or a filler and a vent, if you prefer). This is my first experience having only one filler. I use a short piece of fuel line on the filler and fill the tank with a CA syringe (it has only had fuel in it). When the tank is full, excess fuel leaks out around the tubing/filler joint. I was wondering if I could be flooding the engine by pressurizing the tank. I think that would only affect starting, not the eventual sagging, but who knows?

In any event, I want to try all the non-destructive stuff before I go removing metal.

Thanks for the help!


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Post  pkrankow on Sun Apr 28, 2013 6:35 pm

The head gasket helps considerably although a good seal can be had without. There should have been one in there. I have run these engines sans head gasket before, sometimes they do run BETTER like that, but not normally.

As long as the vent is also plugged, and the needle gently seated blowing air into the tank should be adequate. A little fuel may make a leak more visible.

There is a vent next to the filler tube. The vent is a little hole.

If you are "hot fueling" a running engine it is (theoretically) possible to flood the engine and stall it that way, but it is not easy to do (I have never stalled an engine this way, and I hot fuel regularly). As soon as the fuel syringe is removed the engine should stabilize again. Pulling vacuum and starving the engine lean is easier than flooding while hot fueling, but again this is not easy to do to the point of stalling the engine and it will recover very quickly when the syringe is removed (I have stalled engines this way, deliberately, likewise covering both vents on a stunt tank will stall the engine IF there are no air leaks).

Phil
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Post  RknRusty on Sun Apr 28, 2013 7:24 pm

Some may run without a head gasket, but It's meant to always have at least one, two if you use 20% fuel, and add one for every 10% after that. That's likely the reason for your compression loss.

Phil is right, there should be a pinhole vent next to the filler tube.

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Post  flyjsh on Sun Apr 28, 2013 9:08 pm

Okay, I did a little looking and testing....

I found the pin hole vent.. It was hidden by the tubing I had on the filler Embarassed I filled the tank, closed the valve, and sealed the vent best I could: no leaks as far as I could see. Just for fun, I swapped out the head from the Sure Start (known good... and it didn't have a gasket either, hmm), and snugged it down well. The compression seems a good bit better.

Hopefully, I can give it a shot tomorrow and report back.
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Post  Cox International on Mon Apr 29, 2013 11:33 am

We are sorry to hear that one of our products did not meet or exceed your expectations.

We have come across a very small amount of .049 Surestart engines where the glow head gasket was not installed by Cox when they assembled the engines.

For our Babe Bee engines we use the front and top ends of a Surestart engine; taking off the backplate and adding a fuel tank assembly; without actually removing the glow head.

Please identify yourself to us at support@coxengines.ca and we shall send you some glow head gaskets as well as a little gift for your troubles.

Our apologies...

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Post  flyjsh on Mon Apr 29, 2013 7:02 pm

Cox International wrote:We are sorry to hear that one of our products did not meet or exceed your expectations.

We have come across a very small amount of .049 Surestart engines where the glow head gasket was not installed by Cox when they assembled the engines.

For our Babe Bee engines we use the front and top ends of a Surestart engine; taking off the backplate and adding a fuel tank assembly; without actually removing the glow head.

Please identify yourself to us at support@coxengines.ca and we shall send you some glow head gaskets as well as a little gift for your troubles.

Our apologies...


Thanks Bernie. Things happen, and I am not in the least bit upset. I just wanted to be sure it wasn't operator error before I bothered you.

I'll drop y'all a note.

Thanks.
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