honda gx390 rusty cylinder

[Az Shadeguy]

Thanks I ordered a caliper.
Since I have a mill which I hardly know how to use I am going to attempt to over bore the cylinder.
If 88 mm is standard I am going to try for a .25mm oversized piston so that would make it 88.25mm right?

[KE4AVB]

That right about sizing but I would wait until you are finish on the cylinder clean up as you might need a size larger. This something I have learn on the small engines as I have a few that didn't straighten out until it was beyond repair and I had already ordered the parts. The last engine I did the taper didn't clear up until at .019" over and only a .020" over was available. On top that I ran into inclusion air pocket in the liner but was lucky that on was only the skirt area and not the ring travel area.

[Az Shadeguy]

Yes I will wait until I am done before ordering the piston
I will shoot for .25mm but I can go to .50 or .75mm

[Az Shadeguy]

Ended up going to .50 seems to work fine