TRX .15 Pro engine will not start!

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gothamite

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I have an old nitro stampede with a TRX .15 pro engine. I bought it used and have had it for years, but never have gotten it running well. Recently, I got it out again to try to get it working. I completely tore apart the engine and carburetor, cleaning and lubricating the parts thoroughly. To my dismay, I still couldn't find much that looked broken or overly worn. The piston and sleeve weren't scored or damaged (though they were discolored in some spots), the bearings were fine, and the crankshaft seems to be fine as well. The only thing that was obviously broken was the backplate gasket. I didn't have a backpate gasket on hand and I couldn't find one for sale, so I just put the engine back together with the broken gasket and sealed all the potential problem areas with Ultra Copper. I set the carb to factory settings and proceeded to try starting it. It occasionally buzzes for a moment and then quits, but never completely comes to life. I then played with the carb/ throttle settings, but still nothing. I don't think the problem is anything really obvious; I know that the engine is getting fuel, the glow plug is igniting, and that the flywheel is tight. I feel like there is decent compression because it is fairly difficult to turn the engine over by hand. I am really at a loss with this one. Could a torn gasket really prevent the engine from starting at all? I feel like the symptoms could suggest that the piston sleeve is bad, especially since I know that this engine has been run too hot before, but there are no signs of damage to the sleeve and there is decent compression... so idk :\

If you guys have any suggestions I would love to hear them. Thanks!!
 
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A worn engine (piston and sleeve) will usually not show visible signs of damage.
To check the piston/sleeve fit it is best to remove the piston and sleeve from the engine and then insert the piston into the bottom of the sleeve. If you can then push the top of the piston even with or past the top of the sleeve without excessive force they are worn out and need replaced.
If it is worn out, the little pro.15 engine is not worth a rebuild unless you are doing it just for the experience.
If the piston stops a fewmm before the top of the sleeve and there are no scratches/gouges in the sleeve walls or piston sides the compression should be sufficient enough for the engine to run.
A broken/damaged gasket on the back plate can cause the engine to not run/tune well if its leaking, but it shouldn’t keep it from running unless it’s a very bad leak.
 
Well I took the piston and sleeve out to check the fit, and, if I don't force it, the piston stops about a mm or two from the top of the sleeve. I inspected the sleeve and piston for scratches, but found none. In fact, the piston and the inside of the sleeve are pretty smooth and polished. I don't think that the leak is too terrible. The gasket still fits in place as if it weren't broken, as it is only torn in one place. Anyway, if I do decide to replace the engine, what is the deal with traxxas's engine trade in policy? Does the engine still need to be under warranty?

-Thanks
 
The Traxxas program is for all of their engines. You pay a set fee and send the core engine and they send you a new engine with a warranty.
 
Dont forget you can also upgrade to the 2.5 or 3.3 through that program and it doesn't matter how old or broken your engine is! You can even bring your current engine in pieces and they will still accept it lol, seriously.

I know when I traded my 3.3 for a new one it was only $110, not sure what it would be for you but it's worth upgrading as in my experience the 2.5 and 3.3 are a much better engine, both seem easier to tune than the .15, and easier to get parts for as well. Not to mention more HP! May be worth your while...
 
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