Hello Scotty:

I have the similar problem with the OS 91FX on my UCD60. I found the dead stick was always due to the engine overheating. There are separate reasons and it can be corrected.
1. Cooling, make sure there is more area in the outlet of the cowling than the inlet to allow sufficient air flow.
2. Let the engine run a bit richer on the ground. It will lean out in the air. This will avoid overheating.
3. If you use an auto filler, make sure there is no leak or the plunger is fully released after fueling. This can cause the engine to run really lean on high throttle. Try bypassing the auto filler.
4. Check the head gasket screws to be sure that they are fully seated.
5. Check your propeller pitch. It runs well on 15-4W or 14-6, because the engine likes high rpm.
6. The OS engines require a long time to break in fully (may be several gallons). You may need to let it run rich for a while and have patience with it.


Hope these suggestions help. It did on mine.

IDM