I have a lst with a stock mach .26 engine in it. I use 20% fuel. I was told 220 was a good temp but for me to have fun with it it runs around 240. Is it bad to run it hotter than 220 or no?

No, 240* is probably about right in all honesty. Lots of people run them at 280* or more and never have a problem. I dont even use a temperature gauge. If the engine is tuned good and has no air leaks the temperatures will fall in line.

ok thanks because I wasnt sure if it would weaken the metal inside and bend