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Have an 03 TB, wouldn't run, PO beat the hell out of it. Original carb wouldn't send fuel, swapped it with a carb from a 00 TB, so now running premix 32:1, no oil injection. Changed a bunch of parts, here's the ones that matter; new crank seals, new OEM stator/magneto assembly, new aftermarket coil, new plug, new and oiled air filter, new manifold boot. Rebuilt top end with Wiseco .5 over, bored and honed, Winderosa gasket kit.

With the 00 carb, got it to fire and start. Once it's running, it'll increase throttle on its own. Cable isn't hung up or binding, nor is the spring in the top of the carb binding.

Tried it again today, went to wide open again. Turned gas off, hit the killswitch, and pulled the key...kept running. Pulled the plug for the CDI and the black wire from the coil, still running. Pulled the boot off the plug, still running. Pulled the stator wires, still running. At this point I thought it was bound to blow up, but after 45 seconds or so of pretty much disconnecting the wiring harness it finally puttered out.

Thinking crank seals for the throttle running wide open, but continuing to run after everything is pulled got me stumped. Any thoughts, solutions or opinions to anything above would be greatly appreciated.

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Two stroke engines can and do diesel - it's not that uncommon and many factors are involved - it can be caused by glowing carbon on the piston, cylinder head or spark plug. It can be caused by the fuel or the oil mixed with the fuel. It can be caused by the fuel/air ratio. It may be attributed to compression ratio or an unchamfered port in the cylinder.

Sometimes when seemingly revving wide open with no ignition, opening the throttle will kill the engine.

Start with the outside variables - check the combination of fuel (brand and octane) and oil (brand and base) - mineral and vegetable oils can burn and burn hotter than gasoline. The fuel/oil combination may be conducive to an uncontrolled burn. The fuel/oil may be releasing oxygen during combustion providing an uncontrolled combustion (the fuel/oil is providing oxygen to support combustion without the throttle being opened - somewhat similar to a solid rocket fuel).

There is only a few ways to stop a runaway combustion - remove the fuel source, open the combustion chamber (no compression), lean the mixture (more air or less fuel) or flood the engine (all fuel, no air), replace the air with a non-flammable gas (carbon dioxide, halon, carbon monoxide, argon, helium etc), overload the crankshaft (engine brake) or possibly restrict the exhaust filling the combustion chamber with spent gasses and preventing additional combustion.
 

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The quickest way to snuff an engine is cut its air supply.

If it does it again for any reason, plug the air intake, even if it means taking your shirt off quick and stuffing it in the airbox.

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