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Well fellas i need some help compiling a list of Mac piston pin part numbers and there sizes along with there various lengths and wether there closed or open. Steve your help is needed.

McBob.

Fellas i have a Wiseco .060 o/s piston for one of my rebored 101's and the pin length is 1.630 would any of you happy campers have one and if so i could pay you via paypal for the pin and postage to Australia.

McBob.

what diameter pin? if it's 1/2" I have some NOS saw pins that are 1.670"

Tom Smith wrote:what diameter pin? if it's 1/2" I have some NOS saw pins that are 1.670"

Well as truth be it the pin i need is .565 or close too and 1.325 long i just sized it with my dial caliphers.

McBob.

how about cutting down an SP-105 or SP-125C pn89204 pin? they both used the big pin only it's longer than you're looking for because they didn't use a backport style piston. I believe the actual pin you need is from an Mc-75, Mc-100, Mc-101, or else a 797/Super 797 powerhead which is basically what the Mc-101 is. The Mc-70 still had the 3rd port passage so I don't think they used a narrow pin. The 3rd port passage feature was to allow easy starting and a smooth idle which mostly went out the window the first time someone really 7, 8, or 9 ported a Mac for open racing.

Next question Tom i have another .060 O/S piston with the 1/2" pin now how the dicken's do i get the pin out after it's been fitted without destroying the closed needle cage ???

McBob.

Maybe you could push the pin and the closed end bearing cup thru a hole cut in the piston if it doesn't already have one. The bearing cups are brittle so I don't know, you might end up pushing the pin right thru the end of the cup. Heat the piston first. Usually I press the pin out right thru the piston wall in a hydraulic press instead of using a hokey pin puller tool. I don't save used bearings. I checked a used 9/16" x 1.325" pin that I removed from an earlier model 125 saw so it's a standard Mc pin. I'd switch it to the Mc-101 shorter 1/2" rod and piston combination myself, those parts are much more common. Piston in the photo was a new under cut and lightened 101 piston that the top ring pin backed out of so I did save this one to salvage the bearing cups from someday.

Now i am idead indebted to a friend i lost a few years back as i sorted again what he had left me that included standard sizes for the use in a SP125 as Chris raced them as well so i have 797 pistons and SP125 pistons to keep the Mac's roaring for a few more years yet so i'm grabbing what else is needed in the way of rods piston pins and pin bearings i have plenty of standard rings here as there's no reboring those chrome cylinders so again i collect what i can .....................

PS i cut and trimmed a piston pin this morning following your suggestion thanks Uncle Tom.

Mc Bob.

It's not pretty, but I wasted 3 old taps tapping the ID of a piston pin and pulling it out. Saved the rod & piston but junked the pin.