72 125 Alternate Piston

I have a 72 125 with some other brand piston. Not normal piston. Anyone know of piston of another brand conversion? Trying to find out if there was also a porting change to go with it.
Replace the piston with short style. Bike will only run if I prime the carb by hand with fuel. Runs perfect for 5 seconds and dies.
Did everything from carb and pressure test engine.
This is all beyond bizarre.

Rob

I know wiseco made a piston back in the day. If you still have a short rod in the bike you need the piston to match. Vintco sells long and short pistons. Sounds like you have fuel issues to me.

Have new carb coming. So bizarre. Everything checks on on one I have.

Thanks

Rob

Just curious...what type of "new carb" do you have coming????

I should say another carb. 935 L21
Seems like fuel issue, don’t see anything wrong with carb I have but easier then tearing down the engine.