ORIGINAL: SyCo_VeNoM
sounds like the pinch is shot. Happened to me on my 1st nitro (got it used also). Ran perfectly find for 5 minutes but once it warmed up the parts expand and it loses compression.
there is 2 ways to check it, and how bad it is that I know of.
One take out the glow plug and rotate the flywheel. If it has no resistance at all when the piston is at the top of the stroke good chance its the pinch. Other way is to dismantle the motor itself and see if the piston can be pushed out of the top of the sleeve.
there are generally 3 remedies I would price em all out
Take the motor apart and check if the piston and sleeve are in good shape (no scoring the piston head isn't black etc...)
If the piston head and sleeve are in great shape one option is to send the piston and sleeve to RayA at
http://www.rayaracing.com/ he charges a small fee but it generally is cheaper than a new piston sleeve combo (I've read alot of good stuff about his work, never tried him personally)
Other is replace the piston and sleeve with a new set.
3rd option is to just buy a new nitro engine.
In my case on my 1st nitro it was the to replacing the engine cheaper option seeing the engine I had was discontinued and parts cost more than a new, better rated, more modern engine.
For future reference if you ever get a used vehicle again. When paying for it (or trading) think of the engine as if previous owner had no idea what he was doing, think of it as shot, and figure in the price of a new engine in your trade. Every engine I've got so far in a used nitro was totaled and makes very nice paperweights.
Just hope you didn't get as big of a lemon as I did on my 1st nitro I had to replace over 90% of the parts (spur gear, diffs, chassis, and dogbones all that are left from the day I got it) in under 4 months of owning it due to parts being brittle and cracking.
Ohh yea welcome to the hobby
Forgot to add Your gonna learn ALOT more about nitro (and the trucks design in general) seeing you got a used vehicle than if you bought a brand new one if you stick with it