Stumped!!
I put an OS .18 in my nitro rustler a couple of months ago. Today it started to run hot. I turned the high needle out about a qtr. turn. Still the same problem and it cut off at idle. I tried to change out the glow plug (same thing). There doesn't seem to be a air leak since it cuts out when I plug the exhaust.

Any ideas??

Dirty carb, restricted needle/ spray bar
Air leak, fuel/ feedback lines/ fuel tank
Loose engine component, backplate/ starter holder/ cylinder head
Clutch/ spur setting too tight, excessive clutch shoe wear and heat

I find that the first and second causes are most common.
Plugging exhaust is an overwhelming backpressure that will eventually shut off any engine, and does not rule out possible air leaks. You are using a fuel filter, aren't you?

The inside bearing on the clutch bell went bad.