cox .049 start problems

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cox .049 start problems

Postby kennyk27 » Mon Aug 31, 2009 11:02 pm

I am trying to run what is a cox .049 on an engine pod to launch my glider. Bench testing the cox, it is hard starting; when it does start it does so for maybe 10-12 seconds and quits. I have read about starting cox engines and how to start. they must be tempermental. I am using 1/2 a Byron fuel .25% methane with castor oil. I bought this on the ut internet, is supposed to be new but am running out of options for sustained starting.

Is my fuel tank positioning critical? My intake is right above the fuel supply hose on tank. AM using just a 2 oz. tank.. if I go bigger will it increase fuel pressure by gravity?

I have started out by a couple drops of fuel in exhaust return tube.. open 2 and half turns.. pops.. open half turn pops and runs.
also tried 3 and half turns ..pops.. close needle half turn..pops..same..close needle..pop and runs about 10 seconds??? Help!!

If someone out there has an .049 to .070 engine known to run give me a holler thanks.
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Postby gossie » Tue Sep 01, 2009 3:25 am

25% nitro mix fuel should make it run. But they do like more, like 40, 50% or more.
Is the plug good? Is it glowing bright with a good 1.5v battery?
I assume it's reed intake motor not a TD......Is the reed sitting properly?
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cox .049

Postby kennyk27 » Tue Sep 01, 2009 6:06 am

Thanks for reply Gossie:

I haven't fooled with these little motors since I was a child.. I guess I didn't learn much about them even from then. I don't know even where to find 40% or more hi test fuel. Hobby shop? Also I am assuming I have the reed set up.. with fuel assembly unit away from motor there is a metal plate inside the plastic housing. How can i find out if it is working or positioned properly? Not to sound more stupid, what is the TD setup?
I like the little engine concept but need some serious heads-up on these "details".. appreciate any advice you can give me. ken

Also, I just need this motor to run about 50 seconds reliably to launch a 2M glider high enough to catch the thermals.. hope the little motor weight isn't too much of a hamper.
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Postby gossie » Tue Sep 01, 2009 3:10 pm

The TEE DEE COX engines are front rotary induction......i.e. the carb. is in the front.....the crankshaft has a hole in it and hollow allowing the mixture to enter the crankcase.
The reed engines are rear induction. It may be worth your while to pull it apart just to make sure the reed is sitting properly and perhaps not glugged up with old stale fuel/castor oil.......assuming it's a motor that has been run in the past.

What propeller are you using? A 6x3 down to 5x3 is the size, again assuming your motor is an .049.
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cox .049 start problems

Postby kennyk27 » Tue Sep 01, 2009 3:24 pm

Thanks Gossie:
will investigate the reed plate.. was supposed to be new but don't know for sure.. carb assembly in back.. 5 x 3 prop.. gossie are these reliable motors? If I put it on a plane i have taken time to build, my labor is up in smoke if the plane becomes airborn and the cox quits at a critical moment.

You know I had these as a kid 40 years ago with control line planes; I remember quitting flying because they were so tempermental and I spent more time tinkering and trying to figure out what was wrong than I did actually flying. Any imput would be appreciated.ken
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Postby spacebug.049 » Tue Sep 01, 2009 4:27 pm

Boy has this happened to me a lot! Cox engines are known for being very easy to start, so long as you have set it up properly. Usually the 5- 10 second run is because you are too lean. Try starting with the needle valve about 2 1/2 turns out and move it in or out based on what happens after it starts. The venturi might be blocked up if it has not been run in a while. Take a really small needle and push it down through where the needle valve goes. If you can see the point of the needle, than that is not you problem. And also check the reed like gossie said. You should hear sort of a pop sound when you turn it over. Not the sound from the piston though.
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Postby chiefss » Wed Sep 02, 2009 10:50 am

25% nitromethane is plenty. Cox blue can fuel was 25% and red can racing fuel was 35%. Reed valve engines that have sat for a long time tend to have the reed gummed up. They can also be bent. Both will make the engine fail to work. The little Cox engines were and are usually very easy to operate.

Open needle about 3 turns to start with. Make sure you have a good battery and a good plug. Just because a plug glows doesn't mean it's any good. I find that the Cox plug with a coil rather than the ones with the two little "prong' looking things work better. Also the Hi Comp plug works better. It comes with the TD's.

I wouldn't stick anything down the needle valve hole. You can enlarge the jet and that will ruin the engine.

Cox engines are very reliable. Cox made at least 25 million of the Babe Bee's alone.
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Postby Jim Thomerson » Wed Sep 02, 2009 11:07 am

I have seen several needles break in tank-type Cox engines. Makes them not work well at all. You may not realize what is wrong until you remove the needle and the pointy part is still in the engine. :cry:
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Postby spacebug.049 » Wed Sep 02, 2009 4:09 pm

If you hammer the needle through it will damage it. Not if you just slide it in there to push any clogged, dry fuel out. I have done this hundreds of times and my engines works great.
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Postby gossie » Fri Sep 04, 2009 2:38 am

FWIW I decided to fire up a TD.051 in a new model I just finished......it had been a while since this one had run.....and all it would do was run for a moment on the prime.
I pulled the carb. and used some very fine fuse wire into all the small holes to make sure they were clear in it, put it back together.....and BINGO, she goes.
Old castor has a habit of doing that, even with a decent flush out and oil up when done for the day.
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