heat on an engine could be generated cause other reasons. If u are running too hot of a plug for the fuel and engine compression then it could be preigniting or pre detonating. This can cause high temps and erratic idle. A drivetrain that is not free (gumed up clutch, bad bearings, ...) can also affect the engine temps.
Here is a link to some very good info. Check it out, re-tune your engine and let us know how it worked out. http://www.parisracing.com/engine_tu...coversheet.htm