So you’ve got an older Tomos(pre-1992) and have decided to put a kit on one. You’ve got a A3 engine and you’ll begin to notice that there’s a much bigger selection out there for the newer style A35/A55 engine. This stems from the Tomos A3 using a 10mm wrist pin with it’s piston and the A35/A55 and all of the Puch setups using a 12mm wrist pin.
The easiest thing to do is just press out the brass bushing in the connecting rod and push in a new one off a a stock Puch crank. One thing to note, the brass bushing setup is really only good up to 8500 rpms, if you’re gonna run faster then that you’ll need to have a new connecting rod pressed into your crank that can made use of a needle bearing.