D I've been pouring through the various spec sheets and noticed a few bikes that are close but haven't really found anything. Several months ago I think I found some Honda bike pistons but the price was more than just ordering what I needed.

If you have detail on what Honda crank I'd be curious as to the details, not that I would do anything with it.

I also looked at Mazda GLC pistons, Rockauto had some that were 78.75mm that worked out to $45 for a set with rings. Some minor machine was needed but the total would be around $250 for parts and labor.

The pin height on RB20 piston seems to be way off for an A15, it seems like milling 2mm off the top of the piston wouldn't be fesaable.

All said and done the larger bore isn't a huge boost, probably no more than 10hp but realistically more like 5-7.

Tom