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Old 11-21-2002, 06:45 PM   #1
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Default Untunable engine

I've posted this to several other forums on the net so I thought I would here as well.

Has anyone out there at all ever had an engine that you had to end up giveing up on once it became untunable? I've had to do just that and after a few months, have decided to break it out and tear it down to look it over. I gave up on this engine some time back after trying to fix what appeared to be an air leak. This engine got new piston and sleeve, new bearings, new carb body, new gaskets...I think that's it. Anyway, I never could fix it.

I've heard stories of the crankcase cracking internally and even the exhuast gases leaking between the sleeve and case bore back into the crankcase.

Just curious.
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Old 11-21-2002, 07:42 PM   #2
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Default UNtunable engine

I had that problem once with an Ofna Colt .12 engine. Only had maybe 1 gallon through it and it started running erraticly. Took it apart and everything looked brand new inside. Tried resealing everthing, put new front bearing in, nothing helped. Finally gave to a friend to use for parts on a XTM engine.

You didn't mention what brand of engine it is, but it sounds like an air leak or worn piston and sleeve. A air leak in the fuel line could cause tuning problems. Plugged fuel filter? Smashed pipe stinger or dirt inside stinger tip. If it is an O.S. .12 and the NEW piston and sleeve were from Duratrax, then that may be your problem. VERY poor quality on the Duratrax P & S.

Last edited by popsracer; 11-21-2002 at 07:49 PM.
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Old 11-21-2002, 07:48 PM   #3
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The engine is an OS RZ-V01B and the piston and sleeve were replaced trying to fix this problem.
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Old 11-21-2002, 07:53 PM   #4
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Default Expensive engine problem

WOW, that is a very expensive engine problem. Did you have dirt go through the engine? Maybe the crank is scored and leaking there.
Other than that I think that you did everything you could. What did you buy to replace it?
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Old 11-21-2002, 07:59 PM   #5
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Heh...another 01B. the engine was a little over a year old when this started happening and, other than that, I was quite pleased with it. It was my first .21 and since I was used to it, I didn't want to change.
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Old 11-22-2002, 02:11 AM   #6
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Did you ever take apart your carburetor?There are many O-rings in the carburetor.Maybe there are a little air leaks there.
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Old 11-22-2002, 10:29 AM   #7
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Yea...all the o-rings and seals were replaced. I'm tellin' ya...this was a good one.

But keep the ideas coming. It's bugging the hell outta me just sitting over here on the bench!
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Old 11-22-2002, 01:13 PM   #8
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Try checking the big fuel cap O-ring of your fuel tank, air leaking there will cause irregular fuel pressure to the engine. No way to get consistent tuning under this condition.
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Old 11-22-2002, 01:27 PM   #9
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The tank had been replaced. All compnents in the vehical are ok...including the pipe and header.
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Old 11-22-2002, 05:43 PM   #10
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Default I know what the problem is!!!

You need to put the engine somewhere very dark. Then in the middle of the night, sneek in and quickly put it in a plastic baggie and seal it. When the Gremlin inside tries to get away he's trapped in the baggie. Be careful they bite!

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Old 11-22-2002, 05:53 PM   #11
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GOOD NIGHT! I think you nailed it popsracer! I'll try that!

Really...that's almost how I feel about it. As if it's nothing tangible.
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