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having trouble getting an Cox .020 thimble drome engine to run

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Old 11-07-2013, 07:00 PM
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EskimoJoe15
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Default having trouble getting an Cox .020 thimble drome engine to run

Hello I have this Cox .020 thimble Drome engine and I'm finding it quite difficult to get the darn thing to run so far i have only made it start and run for about 3/4 of a second.
This particular model is the "Cox Thimble Drome Easy Start model" and the fuel I am using is 30% Nitro, 25% castor oil, and the rest is synthetic oil and I was wondering if the % of nitro would be the problem.
Any tips for starting these engines would be very helpful I am new to nitro so this is my first engine of my own.
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Old 11-08-2013, 08:23 AM
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The Pee Wee is probably the most finicky of all the Cox engines. Sounds like it is only running the prime.
If the engine is a used one the chances are that the back end is full of old congealed fuel and crud.
The little tube in the tank could be blocked.
The reed could be bent or stuck.
The tiny rubber washer is not sealing.
A leak between the case and the tank.
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Old 11-08-2013, 08:34 AM
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It's been a long time since I played with a 020 but if memory serves me correctly it is probably clogged with old castor either in the needle valve or in the reed valve. The first thing I would do is flush it with some straight methyl hydrate to be sure the tiny passages are clear. You can put some MH in a syringe and force it through the system from the tank filler. First remove the needle valve to be sure that passage is clear and then replace it and try again. Put the piston to TDC so the sub piston port is open and force the MH through. If the MH comes out from under the piston the passages should be clear. Replace the MH with fuel and try again. With the old Cox engines cleanliness was nest to Godliness. Sometimes it will take a number of tries to clear it out.
Peter
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Old 11-13-2013, 08:06 PM
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I assume this is a typo:
…the fuel I am using is 30% Nitro, 25% castor oil, and the rest is synthetic oil..
And what you meant to say was:
…the fuel I am using is 30% Nitro, 25% castor oil, and the rest is alcohol
It wouldn’t run on just nitro and oil.
Al
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Old 11-15-2013, 07:50 AM
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Quote:
Originally Posted by Big Al-RCU View Post
I assume this is a typo:
…the fuel I am using is 30% Nitro, 25% castor oil, and the rest is synthetic oil..
And what you meant to say was:
…the fuel I am using is 30% Nitro, 25% castor oil, and the rest is alcohol
It wouldn’t run on just nitro and oil.
Al
I noticed that too. You are probably correct about it being a typo, but I can see how someone could easily get confused because many call them "nitro" engines and do not know that the "burn" comes from a catalytic reaction between the platinum glow element and the alcohol. To top it off most times we talk about nitro content and lube content (percentages of castor/synthetic) and ASSUME everyone knows the rest is methanol alcohol.

George
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