Mcculloch SP125 teardown questions.

[NWCS]

hey all, in the process of tearing down my personal Mcculloch Super Pro 125c that had very high compression.. now i see things i i never expected.. bottom side of the cyl has some nasty scores (dont have the piston out yet) crank bearings are a bit sloppy and the crank seals look bad. the big question is how much can a 125c be honed? or can it be bored out and an oversize piston used? (the 125 IPL lists oversized pistons) and i see a few 101 kart pistons out there in oversize.. the overall plan is a monster mac hotsaw using a kart intake and possibly a kart large bore carb instead of the walbro SDC or tillotson HS124A/B carbs i have. been planning this project for the last 4 years, rather glad i didnt start before now.. wouldnt know what to do without you guys.
how many of the 101 kart engine parts fit? engine bearings for the 101 are alot easier to find than saw engine ones.

 

[Al Smith]

125/101 parts

While the sp 125 and the 101 kart engine seem to be the same,there are slight differences.The cp 125,is more like the 101 ,with regards to the rod bearings etc.Wisco made a 100 thou overbore piston,but they are rare as a hens tooth.If you have a 125C[chrome liner],you are stuck with a stock bore,unless you install a cast liner or rebore and rechrome.Both are costly.The bearings and seals should not be a big deal,as they are SAE size,and not the OEM,used by the orange and white saws.There are several sellers of old Mac parts on this site.I have dealt with them all and can say,they are all good people.Most likely the ultimate carb setup is a Tillotson HR,with a 6 or 12 petal reed set up.If you do this,however,it will not fit under the air box cover,and will look more like a Kart engine,than a saw.There are and were a zillion setups for the kart engines,such as quarter timed pistons,etc etc ,most of which I know nothing about.The big old Macs still got the stuff,but it would be a needle in a hay stack search to find the parts.

 

[NWCS]

i just looked it up and now im confused, the SP125C specs claim cyl spec: alum with cast iron bore. found at: http://www.acresinternet.com/cscc.n...8f3f282a75b10ab688256c2f00198ba9?OpenDocument
so if this is true, i can get a 101 piston.. but how do i truly confirm it has a sleeve in it? any easy way to tell?

 

[Al Smith]

And that picture,of that saw,belongs to me.Mike has done so much on his website,he is constantly upgrading and making corrections to it.That one,however ,slipped by him.I forget the dates,but the sp-125[iron liner] was before the sp-125C,which was 1977.Oz had the dates on a thread,somewhere.That saw on Mikes site had a chrome liner,that was damaged.I,in fact,turned one of cast iron ,to repair that saw.On your saw,it should be easy to tell by looking through the exhaust port,or by looking at the bottom of the cylinder with the saw apart.If it has an iron liner you will be able to tell it,the iron will be darker than the aluminum .

 

[MacDaddy]

I have seen both the sp and the cp with cast and chrome liners the only real way is to look if it has good compression only replace the bearings and enjoy the saw but if you have to have a new piston brace yourself for the cost of one I know I own 40 101 kart motors and about 20 125 mac's I also have about 30 extra pistons I wont part with

 

[galde]

one quick way to check whether the bore is chromed aluminum or cast iron in to stick a magnetized pick-up tool through the plug hole or exhaust port.

 

[100 cc plus saw]

Can I get 6 or 12 reed valve stack that tank and airfilter houseing can bolt up to