Gentlemen,
I suppose if Jaran had asked, "Should I change to 9:1?" instead of, "Can I do it and
what is the part that I have to replace?" I would have kept out of it and left the issue to more experienced folks, as yourselves.
Honestly, I appreciate your comments and must now choose for myself if I want to stay with 9:1 in my own current rebuild. MY '55 A10 has thick flange and alloy head, as I believe Jaran's must. (Jaran, how about commenting here regarding your bike's head and barrels. Thick flange in 12.2 mm.) The reason for my rebuild is a thrashed left-side big-end bearing with signs of oil starvation, so I don't think it was a matter of being at 9:1 vs. 8:1. It seems to me that the crank might have been bouncing left and right from a too-loose cush nut, leading to enough shift in the bearing shell to cover the little oil hole. Another possibility is that the piston was so loose in the barrel that it caused the shift. So you ask, "Okay Richard, why did you let your piston be so loose in the barrel? Answer - I was being cheap and I wasn't confident in the beginning that I would get the engine running. So, I just honed away rust until I had a cylinder wall, figuring that a top-end rebuild was in the offing and doable, if necessary. When the finished engine started on the second or third kick, with no obvious slap, I figured I was in the clear. However, to hedge my bets, I bought a set of 9:1 pistons in the next size up in order to be ready for the rebuild, when necessary. I guess I'll give some more thought as to whether or not to use them.
Regarding valve seats, Dave, that was very interesting information. Are you recommending against lead substitute for any particular reason? My riding miles are not enough ot make it a cost or inconvenience factor.
Well, that's enough for now. I think my insomnia is subsiding.
Regards,
Richard