135cc conversion

Sometime I'm going to need a rebore of my 125cc Cometa. It appears that oversized 125 pistons are scarce (I'm already on an oversize). What's entailed in a 135cc conversion? Are there any drawbacks. I don't really want more power it's just that in the future I will need a rebore.
Having said that I could get away with new rings for a while. Are 125 rings available? From memory I think I'm up to 57.6 already.

Paul

paul, rings will be no problem to get hold of, when i did a 125cc conversion years ago i was missing some rings, just used gp 150 items.
pistons for the 135 i think came from a kawasaki kh400 and from memory these are not only hard to find but expensive when you find them.
another option would be a tv175 piston and rebore as shown in ken herlingshaw lambretta tuning manual.
daz

Thanks Daz. I'll try some GP 150 rings first.

Paul.