I think the Force 25 is more or less the same as the Force 26. The Force 26 does run hot. 260F is a delicate tune on the Force engine. It can easily go over 300F. At 325, I could hear detonation (sizzling sound at idle after a high speed run).After much experimenting, the end result was it needed an extra head shim to handle 20% nitro.

I agree 100% with Fuelman's post, however the extra shim wasn't addressed...perhaps this could be one of those "mechanical" issues he mentioned.

It will run cooler with a shorty OS A5 glowplug. Also, the carb should be sealed to the engine block with RTV.

Also, make sure you don't have the HSN set to lean trying to compensate for a rich LSN. Tune the best you can, richen the HSN 1/4 turn, then adjust the LSN for best take off after about a 5 to 10 second wait at idle. Then retune the HSN, and finally set the HSN back at least 1/8 richer for reliable running.

Do all this at about 1/2 tank of fuel, or even 1/4 tank to allow for leaning as the tank empties.