Mac I 86

[David Luciani]

thick rings  = more friction so the motor will be noticeably slower.
that said it will also last about forever as a runner.

you'll end up with a decent motor for historic untouched.

if you wanna go with less durable but faster here's three methods to get it done.

if you are mechanically handy you can replace the rings with a new set that you modify

• option 1 knife or chisel blade thinner.
  

basically you remove a large amount of side material from the rings leaving the back 1/4 of the rings uncut.
you also need to be absolutely sure not to cut the outer drag surface of the rings.
the idea is to reduce the contact surface of the ring
a delicate and tedious operation.

• option 2
  

step 1 de-tension low ring by heat to bright red bury in sand till cool to dis-temper ring and remove springiness.
step two with a dremel tool and a thin cut off wheel you will need to add a dividing slot in the top ring (ted j. method)
the finished idea is to have a single ring the has a grove all the way around so it looks like two stacked rings.
again no nicking drag surfaces or your ring becomes junk.

• option three
  

pony up and buy a new kart piston that fits
of course if you do that opening exhaust port a little and adding the nine port cuts will seriously wake that motor up.