RE: Irvine 53
I have several Irvine .53's... I have one that will not shut down but runs great... I checked/swapped the carb, checked the back plate and everything else I could think of and nothing helped... Even replaced all the O rings and gaskets... ... Finally out of desperation I attached a length of fuel line to the inlet on the carb covered up the exaust and intake on the carb with my fingers, held the engine underwater and blew like h*ll. It was easy to see the only leak in the engine was out the front of it.. I lloked at the replacement bearings I had from Just Engines and no way are they going to seal the front of the engine... I can see daylight through them... It would seem that for some reason the clearance between the front of the crankshat and the block is a little too large for the oil to make a good enough seal there and thus leaks air... As soon as I have occasion to tear down a "good" .53 I will mic both and see what the differance is...
Like I said I have several of the .53's, 2 .46's, and 2 .25's... They all run great except for this one that doesn't want to shut down....