I have been struggling with this 6-10 for a few weeks (off and on), it will start and run, runs very strong in the cut, but frequently acts very lean when coming out of the cut, occasionally adjusting the carburetor would help but it just would not tune. Then suddenly it would either flood out or run so lean it would stop.
I've had it back down to the short block 3 or 4 times, pressure and vacuum test are great with the pulse pump (automatic oiler) blocked off, very slow leaks with the pulse pump in place...I finally replaced the pulse pump with one fully rebuilt and it slowed the leak fairly well. Did I mention that the crankcase and seals pass pressure and vacuum with flying colors???
I've had 4 different carburetors on it with very little difference in performance.
I finally started pressure testing as the rest of the intake was going together...the insulator (next to the cylinder) was fine, but when I pressure tested with the tank and spacer installed there was a noticeable leak.
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I tried scraping the surface to get it flat but just couldn't get it to where I wanted it, so I secured it on the mill/drill and machined the boss flat.
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I really hope this will take care of it, I'm sure the owner of the saw is beginning to wonder...
If anyone has additional suggestions/recommendations, I welcome all input.
Way back in the beginning of the process, new piston installed.
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FYI, it has the three screw aluminum body pulse pump so make sure you remove the block after pressure vacuum testing or you get to do it all over again.
Mark