Jim,

I use a Raytek temp gun which some have said is not very accurate.
I tested it against a Exergen (Known to be Exact) and it consistantly showed to be about 1 degree off...Not bad.

I was expecting to see between 160 and 180 at idle as seen on previous MT engine break ins.
My last MT engine broke in at about 180 degrees with about 80 to 85 degrees ambient temperature. The piston and sleeve fit was so tight that I had to heat it up with a hair dryer several times because it would get stuck during break in. I always made sure at the end of a tank that the piston was at the bottom of the sleeve, but when starting it would sometimes get stuck.

The new engine was running 230 on same break in needle settings and around 50 degrees ambient temp. I did also notice that the piston and sleeve fit was not very tight.
It has about 15 tanks through it now and I can flop it over with my fingers, could never do that to any of my previous Nova Rossi engines.

I did go through all the normal troubleshooting when I observed that the engine was running hot. I installed brand new fuel lines, new tank, checked needles, and checked that everything was sealed and tight.
I am sending this one back to Mugen, hopefully they will replace the piston and sleeve or just send me a new engine.
I will update everyone on how it goes.

Dbow