This engine has 368 hours and the high CHT just began late last summer. It has no thermostat, no oil/coolant exchanger, system flushed (water only - no additives). I have repeatedly tried to eliminate air pockets by running it up to operating temperatures then shutting it down and removing heat exchanger & radiator caps, opening radiator bleed ports (screws) and tying the tail down (it's a trike) for several minutes.
It idles and cruises smoothly and develops 5500rpm at WOT. If I had a vacuum leak on #3 bank, wouldn't my EGT increase as well due to the lean condition? Also, do you recommend a coolant system flush additive and does back flushing the system pose any problems?
Thanks - Mike