McCulloch Super Pro 125C motor

[Bubba Stump]

I bought a SP125C a while back with the intention to rebuild it and use for some large tree work and Slabbing. I have always wanted one and found one on ebay that was complete but had no spark. The saw looked in great shape and I wanted it bad enough, that I won the bidding at $320. When I got it it was in real nice cosmetic shape and felt like it had real good compression. I installed an electronic ignition module and got good spark. The saw would try to start with a prime but the fuel tank was pretty gummed up with varnish so I decided to rebuild the entire saw. Upon teardown I found everything except the piston and bore to be in awsome shape. The seal on the clutch side had gone out and was packed with redwood sawdust. When I got the motor apart I found the bore to have alot of the chrome plating missing and alot of scratches, the piston and rings also. I thought that I could hone the bore and put a new piston and rings in it but wanted to have a saw mechanic look at it to see what he thought about it. The mechanic said that honing it would not help it because the bore needed rechromed. He said that it would be a waste of time and would not last. I found a site on the net from Australia that said you could not rebore the SP125C cylinder. It also said that you would have to sleeve the motor or find a 101B Kart block for it. I can not find a good SP125C shortblock anywhere that is in decent shape and can't find a NOS or a 101B block either. Anybody ever sleeve one or know where I could get this done? Does anybody have a good one or a NOS or 101B that is in great shape that they would sell or does anybody have any suggestions on what else I could do for this saw to get it back to its former glory without spending a boatload of money on it? Remember, I plan to use the saw for real work so I need it to be able to last.

 

[leeha]

If your going to work the saw i would just go with an original
SP125C block like you have. If you go the 101 block you will
need at least the block and head. You would also have to trim
quite a few fins on the head to clear the cylinder shroud. And
the cost of a 101 block will be pricy.
I would try sending emails to ebay sellers like axeman to try
to find a cylinder. He sells a ton of 125 parts as well as others.
You can also use the early 125 block with iron bore. Just need
the correct piston to go with it. And those blocks can be bored
over size so if you find one thats not that great it can be saved.
Be patient, One will find you.




Lee

 

[Nitroman]

US Chrome can rebore and rechrome the cylinder as long as it has a removable head.

Cylinder Plating | Honing | Repair | Re-Plating | Big Bore Kit | US Chrome Inc Cylinder Repair Company

 

[Bubba Stump]

I have already contacted Axman but have not heard anything. The block that I have does not have a removable head so I guess having it sleeved is out of the question. I was looking at the bore a little more and was wondering if the bore is steel underneath the chrome and how thick is it if it is steel. Why couldn't you just bore it out past the chrome and put a oversized piston and rings in it? Is this not a possibility? I still would like to revive this saw because everything else is in really nice shape. I will keep looking for another block but the last time I saw one come up it looked pretty bad and went for quite a bit of money. I also whent to a local lawn equipment shop and small engine repair to se what they thought of the bore. The mechanic said it was shot and there was not much you could do with it. He also said that he used to have a bunch of old stock mcculloch parts upstairs in the storage room and he thought he had seen a brand new short block for a 125 in a box up there. He said he would go look and if he had one he would just give it to me, no charge. He returned a couple minutes later and said that the owner must have thrown all their old stock parts away because the boxes were all gone. He said he would keep an eye out if the parts were still there somewhere else. What a bummer, a brand new short block for free would have been a very nice find to return the saw to its former glory.

 

[nmurph]

US Chrome can rebore and rechrome the cylinder as long as it has a removable head.

Cylinder Plating | Honing | Repair | Re-Plating | Big Bore Kit | US Chrome Inc Cylinder Repair Company

They will plate blind bores. I have had quite a few done by them. The cost is around $200 unless you have a bunch of the same cylinders done at once.

 

[Jacob J.]

They will plate blind bores. I have had quite a few done by them. The cost is around $200 unless you have a bunch of the same cylinders done at once.

They won't do cylinders that have the integral crankcase like a Mac 125. I've already asked.

 

[Bubba Stump]

Is there anybody else that you can think of, besides Axman from ebay, that is a SP125 buff that might have another good block that they would sell or maybe a Kart builder that might have a 101 B series block and head in good shape?

 

[IEL]

Sorry, the only mac block I have is a s55a that needs reboring. Iron lined.

It would fit, but its only 87cc, so kind of pointless in a 125...

 

[manostihl]

I'm in the same boat man 125c motors are hard to come by as well as the 101b motors

 

[zogger]

copy and paste this into google, good luck

mcculloch 125 site:craigslist.org

 

[Bubba Stump]

Does anybody know if there where any other model McCulloch's that had the same 123cc bore besides the CP125, SP125 and SP125C. I read somewhere that a 895 had the same motor. Is this true or was it 123cc but a different style block? Are there any other Mac's that have a 123cc block that would fit a SP125C?

 

[Bubba Stump]

I forgot, I was going to ask if anybody has ever heard of anybody boring out a SP125C block and sleeving it. I would think that there would be a machine shop or a machinist somewhere who could figure out a way of lining the non removable head block from the bottom. If this could be executed it would save alot of people like myself alot of grief trying to find a good block. I would guess that somebody with some enginuity could figure out a way and make some money if it could be done. I wish that I had the mills, lathes and know how to to try and make this a posibility but I don't. If there is someone out there who thinks they could sleeve one or knows someone who could or thinks they could let me know and we can experiment with the block I have.

 

[blsnelling]

No sleaving or re-plating is required if you get one with an iron bore. They can be bored and fitted with an oversized piston.

 

[Bubba Stump]

I have the Chrome lined aluminum bore block and everybody tells me that you can't rebore it because of the Chrome plating and the fact that it is aluminum. I thought that this was wrong so I took a rare earth metals magnet and put it to the bore and it would not stick, so I quess it really is all aluminum. This is why I wanted to know if anybody had ever tried to sleeve one. I know that the 101B series blocks could be sleeved easily because they have a removable head and the head holds the sleeve in place along with the tight tolerances and the use of hot and cold expansion and contraction methods. I would think that there would be a way to do a solid non removable head block as well. As the saying goes "Where theres a will, theres a way".

 

[OREGONLOGGER]

I have the Chrome lined aluminum bore block and everybody tells me that you can't rebore it because of the Chrome plating and the fact that it is aluminum. I thought that this was wrong so I took a rare earth metals magnet and put it to the bore and it would not stick, so I quess it really is all aluminum. This is why I wanted to know if anybody had ever tried to sleeve one. I know that the 101B series blocks could be sleeved easily because they have a removable head and the head holds the sleeve in place along with the tight tolerances and the use of hot and cold expansion and contraction methods. I would think that there would be a way to do a solid non removable head block as well. As the saying goes "Where theres a will, theres a way".

PM me and I'll let you know what blocks I have...I have a few

 

[nmurph]

Does anybody know if there where any other model McCulloch's that had the same 123cc bore besides the CP125, SP125 and SP125C. I read somewhere that a 895 had the same motor. Is this true or was it 123cc but a different style block? Are there any other Mac's that have a 123cc block that would fit a SP125C?

895's are gear drives at 103cc's.

 

[leeha]

As for the 123cc blocks, You really need to stick with the SP125 block.
The 797 and CP125 blocks have different style decomps that would
need to be plugged and have the older style coil and mount.
Your block with chrome plating is all aluminum. No steel sleeve. If
you were to have it sleeved i bet the cost would out weigh a whole
used saw. Like i already said, Be patient. Mcculloch made a gazzilion
SP125's.





Lee

 

[Bubba Stump]

What would I have to change or modify if I find a 101B block? Could I use most of my sp125c parts or would the crank, piston, crankcase half etc. all have to be changed to make it work? As far as sleeving it, I have sent pics and a description of my dillema to a custome sleeve shop and they have responded saying they have looked at my photos and are conversing between techs to see if this type of block could in fact be sleeved. they would contact me again once they form a plan of attack because they think they can do it. I contacted US Chrome and they have not even responded to my inquiry. Here are some pics of the bore and block that I have. You will see the Chrome is almost all missing except by the ports, other than that it is in good shape and it would be a shame to toss it or use it as a paperwheight if there is a way to fix it. As far as price to actually sleeve it, if it even costs $400 or $500 that would be fine by me because a good big bore saw that can pull a 60" bar with .404 063 gauge ful comp ripping chain would easily cost $1200 or more to buy. Pluss I just love the sound of a sp125 mac with no emissions filling the logwoods with that good old fashioned two stroke noise polution. Anyhow, the rest of the saw all looks almost like it was barely used. I would guess that the crank seal went bad because the saw sat unused most of its life and was only pulled out for that tree that was a dandy. The seals probably dried up and cracked and when the saw was used for the biguns it sucked in a ton of redwood/cedar dust and dirt and sandblasted the chrome plating right off the cylinder bore, not to mention it was running way to lean because of the loss of ring seal. the air filter and carb compartment looked like it did the day it rolled off the assembly line. The fins on the block look dirty because the sawdust and sap was cooked to it. I will wait around to see if another block presents itself but ussually they goView attachment 308508View attachment 308510View attachment 308516View attachment 308522View attachment 308533 for a premium and there are a hundred other people wanting it besides me. I wish that a aftermarket company would start producing replacement cylinders and pistons for this popular saw like they do the Stihl 090's. If I were a machinist I would mill me some custome blocks to fill the demand for chainsaw guys and Karters alike.

 

[leeha]

That block is toast. And why would you spend 400 to 500 to have it
fixed is beyond me. You could buy another saw thats a great runner
for that price.
As for using a 101, Like i already said, You will need the block, head,
piston and coil. Your crank should work although it carries a different
part number. I think the difference is the 125 has bolt on weights and
the 101 has welded weights like a 797.
Finding parts at the right price takes a bit of time sometimes. Sounds
like your a bit impatient. Remember, Rome wasn't built in a day.
I've had projects in pieces for months looking for the correct parts.
But once done it was well worth the effort.





Lee

 

[blsnelling]

I'm not overly blessed with patience either. But I wouldn't think a block like you need would be too hard to come by. You've just got to find the right contact. You might try Terry Ives. He might have connections with a stock saw cylinder.