RE: Jett 50 problem
I see a three bladed prop in that picture - what are you actually flying it with? It could explain a few things. Overloaded pusher engine, feelin' "hot hot hot", loosened head bolts, plug change, rotated sleeve... ? That situation has been documented here more than once.
If that is a 10-8 3 blader, especially on a pusher setup, it should be on a sport timed .60, not this engine. Heed Jett's instructions about rpm!!! Let it spin!!! I would not put more than a 10-6 2 blade on an SJ .50. Normal advice in the RC fraternity is to reduce prop load a touch on pushers, two strokes run hotter the more you load them up, especially when you exceed a critical threshold defined by the design of the engine and pipe tuning. In general overpropping a 2 stroke is cruel, not kind. Esp a new one, and double-esp if you are overloading it on a tuned exhaust setup.
Bob will undoubtedly arrive here and clear this up. I bet $5.43 on an overheated engine and rotated sleeve or some heat related issue. Search this forum for rotated sleeve and I bet you find some insight. If I am out to lunch here I owe you $5.43.
MJD