rule 0f thumb on a cast piston is about +-.003 as optimal, Forged pistons require a bit more as they expand more when heated up
This is the first time I've had this issue with one going bad instantly. And was curious what the clearances were supposed to be. I spent some time lastnight cleaning up the p/c, and the piston slides right in. The only spot that concerns me is on the sides of the piston skirt is alot tighter to the bore then the middle of the skirt. Gonna go around the ports with a diamond ball quick to make sure that isn't an issue. Then will try again if all looks good.
Given the circumstances, you could flat file and sand those tight areas until a .002 or .003 feeler gauge goes in. I've sanded high spots off a rough piston before, but just to remove light scoring in an otherwise good piston. If it's smooth and the right size it'll work. All a piston has to do is fit smoothly and fill the hole. There's a whole lot uglier pistons running in everyday saws than what yours is
Thank you. You just answered the next question I was thinking about asking. [emoji2] [emoji2]
If it's the right size, that piston will perform just fine
hard to get a good pic. But there is some lines running up it. Took 220 grit emery cloth , diamond ball around ports, then scotch brite.
It sure doesn't look like there's any in there. If you have feeler gauges, I'd still try to make the gap more similar all the way around the piston. Gotta have a couple thou for oil
That's what it looked like before this all hapoened. But has a couple more score lines in it now. They are mostly all on the bottom half , so shouldn't hurt compression.
When checking with a feeler gauge, I had .0016 clearance around piston skirt. I put a feeler on each side at the same time. That's with the piston in the cylinder with top against squish band. When I bring the bottom of skirt even with the bottom of the jug it's a little tighter yet. Have to really push them in.
Sooo....0016 each side for a total of .0032? Or .0016 on one side while the other is tight?
I put one on each side. .0016 if I tried to slide a .002 with a .0016 it wouldn't fit. But when the skirt was even with the bottom of jug they wouldn't fit.
I used 2 of these
