Mac I 86

[ken northside]

i picked an I 86 that had been cruelly made into Kart engine for $5. at an estate sale the other day. this one looks to be a 100CC engine like a 45. Popped it apart and it looks good  crank looks good, bores good, Piston is a thick ring one do the thick ring pistons make that much less power than a thin ring piston. I was think I would just put seals and gaskets and manaifold  on it tomake a cheap runner out of it.  Ken

[Terry Sullivan]

i picked an I 86 that had been cruelly made into Kart engine for $5. at an estate sale the other day. this one looks to be a 100CC engine like a 45. Popped it apart and it looks good  crank looks good, bores good, Piston is a thick ring one do the thick ring pistons make that much less power than a thin ring piston. I was think I would just put seals and gaskets and manaifold  on it tomake a cheap runner out of it.  Ken

Good deal!
The thick rings do create a little more friction, but I think you are right - do the seals and manifold and hit the track!

terry

[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.

[ted johnson]

When the thin ring Mc6 came out, McCulloch was very distressed by the feedback they got. The ?100 Mc6 was eating their $125 Mc10's for lunch. The difference was amazing. Same displacement, both similar engines, but the Mc10 had the thick ring piston. McCulloch did some scrambling, and the last production runs of Mc10 came with a thin ring piston, as did the new Mc20. Of course, just before the Mc20 came out, Mac released the Mc10 stroker kit, and the smart guys installed that into their Mc10's instead of buying the new more expensive Mc20. Lo and behold! The stroked Mc10's had no trouble beating the new, wonderful Mc20-but that's another story! Ted