Mcculloch sp125/101b kart saw build thread

[jacob j.]

I had to mike-out some cylinders and pistons today as well.

 

[Bigmac]

I've got a similar one - a version that was popular in the 70's on the Super Series engines.

I have seen a few of those for sale, an a few others, I honestly have know idea what works the best, I am super curious how they end up working out! Mine is going it need port work to match up.


Dang JJ! That’s a lot of cylinders! All yours?

I had to mike-out some cylinders and pistons today as well.

 

[jacob j.]

I have seen a few of those for sale, an a few others, I honestly have know idea what works the best, I am super curious how they end up working out! Mine is going it need port work to match up.View attachment 236876


Dang JJ! That’s a lot of cylinders! All yours?

Interesting - the opening on your muffler is a lot smaller than others I've seen. I don't think it'll be too much work to port match it though - is there enough meat on the flange to do that?

Yep - all cylinders for builds I'm doing this spring/summer. .030" over 125 x 2, .010" over 125 x 1, stock bore 797 x 2, stock bore 101b x2, stock bore 125c x 1, and .020" over 125 x 2.

It's ironic - a couple guys on Facebook told me the other day that I don't know anything about McCulloch engines after I told the one guy that his 795 crank won't directly swap over to a 125 engine.

 

[Bigmac]

Interesting - the opening on your muffler is a lot smaller than others I've seen. I don't think it'll be too much work to port match it though - is there enough meat on the flange to do that?

Yep - all cylinders for builds I'm doing this spring/summer. .030" over 125 x 2, .010" over 125 x 1, stock bore 797 x 2, stock bore 101b x2, stock bore 125c x 1, and .020" over 125 x 2.

It's ironic - a couple guys on Facebook told me the other day that I don't know anything about McCulloch engines after I told the one guy that his 795 crank won't directly swap over to a 125 engine.

Ya there is plenty of material to port match, it’s not a big deal, kinda wanted to post it so people knew it wasn’t a bolt on! It’s actually a pretty thick casting in general, the out let is larger, I might end up making an outlet cover to adjust the opening to see what works the best.
That’s a lot of Big Macs Jacob! Will be cool to see them running again!

That’s funny, got to love it when someone is wrong and try’s to say you don’t know what your doing, their loss! There are a lot of internet experts out there! Lol

 

[jacob j.]

Ya there is plenty of material to port match, it’s not a big deal, kinda wanted to post it so people knew it wasn’t a bolt on! It’s actually a pretty thick casting in general, the out let is larger, I might end up making an outlet cover to adjust the opening to see what works the best.
That’s a lot of Big Macs Jacob! Will be cool to see them running again!

That’s funny, got to love it when someone is wrong and try’s to say you don’t know what your doing, their loss! There are a lot of internet experts out there! Lol

Randy's right - there's just too many knuckleheads on Facebook.

Yeah, these GEM mufflers I think are too free-flowing for a long-bar saw application. They're made for wide-open high revs on the track. I know the hydroplace racers
used to baffle their pipes in the 80's with some funky configurations to get off-the-line power.

I've got some unusual plans for some of these rigs - a couple will be given away as gifts to old-school retired loggers who put 40+ years in the woods. Three or four others
are getting custom paint jobs. One of my dad's saws will end up in a metallic candy purple - his favorite color. A couple will be ported hotsaw/GTG rigs with two or three carbs
on custom intakes. I might try designing and gas-welding a pipe this summer.

 

[Bigmac]

Randy's right - there's just too many knuckleheads on Facebook.

Yeah, these GEM mufflers I think are too free-flowing for a long-bar saw application. They're made for wide-open high revs on the track. I know the hydroplace racers
used to baffle their pipes in the 80's with some funky configurations to get off-the-line power.

I've got some unusual plans for some of these rigs - a couple will be given away as gifts to old-school retired loggers who put 40+ years in the woods. Three or four others
are getting custom paint jobs. One of my dad's saws will end up in a metallic candy purple - his favorite color. A couple will be ported hotsaw/GTG rigs with two or three carbs
on custom intakes. I might try designing and gas-welding a pipe this summer.

Ya I am a little worried about long bar applications, but I am optimistic. The overall volume is similar to the Mac box muffler and the opening is a little larger exit. Lee’s dual port would have more open area on the exit I think, so looking at it it’s kinda in between, that’s what’s making me optimistic, even a spark screen would help potential. Testing will tell, and worse case it might work for short bar fun saws! The wb saw was turning 10k-11.5k in the wood according to the acoustic rpm tac. So I don’t think I want tons more rpm! Lol
here are some comparison pics

I am excited to see all those builds! That’s going to be awesome!

 

[Lee H]

It's ironic - a couple guys on Facebook told me the other day that I don't know anything about McCulloch engines after I told the one guy that his 795 crank won't directly swap over to a 125 engine.

I hear ya there JJ, I got into it with a Ahole about his Homelite Super 2100 with the 7/8 clutch, he had the wrong
guard on his saw. It's that part that goes over the clutch and bar studs. His was for a 3/4 clutch. He argued and
didn't want to listen to me. Told me i know nothing about chainsaws. His grand daddy bought his saw new. Like he
knew what his grand daddy did with the saw before he was even born.

 

[jacob j.]

I hear ya there JJ, I got into it with a Ahole about his Homelite Super 2100 with the 7/8 clutch, he had the wrong
guard on his saw. It's that part that goes over the clutch and bar studs. His was for a 3/4 clutch. He argued and
didn't want to listen to me. Told me i know nothing about chainsaws. His grand daddy bought his saw new. Like he
knew what his grand daddy did with the saw before he was even born.

Yeah Lee - just because you've rebuilt a few hundred classic muscle saws doesn't mean you know anything...

I thought I'd point this out to you guys - the seller indicates the bore is 2.371" which means it would be about .090" over (huge!)

The liner looks pretty thin from what I can see:

https://www.ebay.com/itm/VINTAGE-KART-GO-CART-MCCULLOCH-MC101AA-BLOCK-2-371-DIAMETER/254574339863

 

[Scott Kelsey]

I am hoping I can jump into this thread and ask you guys a question. Do you feel the 125 series/797/CP125 saws would do at running bars in the 40 inch plus range with 1/2" pitch chain? Considering watching raker height, type of wood, etc. Would it be to hard on those saws and their clutches? Thanks for any insight and hope Bigmac does not mind me asking.

 

[Bigmac]

I am hoping I can jump into this thread and ask you guys a question. Do you feel the 125 series/797/CP125 saws would do at running bars in the 40 inch plus range with 1/2" pitch chain? Considering watching raker height, type of wood, etc. Would it be to hard on those saws and their clutches? Thanks for any insight and hope Bigmac does not mind me asking.

I don’t have any experience with 1/2 chain, but a stock 125 will pull .404 on a 42” bar with 8 pin in softwood, so i think you could pull a 6 pin 1/2. That’s all I seem to see for 1/2. Do you have a particular setup you want to try? I didn’t have any clutch slipping issues with 9 pin 3/8 on a 50” bar on the wb, my stock 125 would probably prefer 7 pin with .404 over 36” bars. 50” bar on the stock 125 liked 8 pin 3/8, saw felt perfect with that setup to me.

 

[Scott Kelsey]

Bigmac,

I have a few NOS McCulloch 6 tooth spur sprockets for 1/2" pitch and a couple rolls of NOS 1/2" pitch chipper chain. Wasn't sure if I would try it on either of my 797s/sp125 or part ways with it. I have a 42" bar it would work with. Was just curious on your guys experience as you have just that, more experience.

 

[Bigmac]

Bigmac,

I have a few NOS McCulloch 6 tooth spur sprockets for 1/2" pitch and a couple rolls of NOS 1/2" pitch chipper chain. Wasn't sure if I would try it on either of my 797s/sp125 or part ways with it. I have a 42" bar it would work with. Was just curious on your guys experience as you have just that, more experience.

It’s up to you, the chipper isn’t going to be super fast, I don’t think, but it could be interesting to test, and I am sure you could easily sell the loop if you don’t like it. I am going to do a test in the future with 9 pin 3/8 and 8 pin .404 both on 50” bars also have a 64” bar to throw in there, that will probably be best on the 090g, will see! I will have a 60” test log available soon, just been too busy at work, and this virus shut down isn’t helping!

 

[Lee H]

I personally didn't like the 1/2 inch pitch chain on any of the 123cc Mac's. Ok on the geardrives.
I had a couple saws that were set up with half so i tried it. Had a couple of Homelite 2000 or 2100's
with 1/2 as well. I converted back to 404. Homelite offered 1/2 in in the 2000 and 2100 saws
but i think it is just a bit much and the chipper chain isn't fast at all. 1/2 chisel might not be to
bad. I save all my 1/2 chain for the geardrive saws i have.

 

[sawfun]

I got a barn find PNW loggers regular 797 that came with a 36" bar, 1/2 chisel, and a 7 pin. The saw runs fine but the bar had an issue and the chain is dull so I never tried it.

I have ran a 2100 with a 60" bar and 1/2" chisel. The rakers were down .020 which worked great on the 3100, but horribly on the super 2100 with 7/8 clutch.

1/2" chisel on a 101b with a 36" bar or less and big carb should work well, but a 125 ain't a gonna like it at all.

I agree with Lee that the 1/2 stuff works best on big gear drives. The 1/2" chipper is slow, but clears chips better then .404 full skip chisel on some geardrives. Some of the big Mac & Homie stuff had 9/16 and even massive 5/8 chain, albeit on 30" length (proudly max length) bars for the 5/8. The 7-29 is the only one man saw I know of that is factory rated to pull a 72" bar with either 1/2" or 9/16" chipper or chisel. Others may pull that length, however most are only rated for 60". Though some Titan twins are rated to pull 144" bars with 3/4" chain. I only have the smaller 132" for my little ER.

 

[Bigmac]

So I’m getting ready to send some stuff off to Terry, and was checking to see if I had the right dsp valve for my CP. It was supposed to be for a 797, but I think it’s for a 795. I pulled the DSP valve out of my 797 and it’s quite a bit shorter, and works perfectly in the CP block. Looking at it, all I have to do is drill a new hole and shorten the 795DSP valve. Could probably also have my machinist friend make me a couple of copies of the 797 valve out of stainless steel, I don’t see them for sale often!
I have been talking to Terry for a little while about this build, and we’re going to do some pretty fun things! Just hoping it all works out! LOL

If anybody has any cart or 797/CP 125 or kart 101 cranks laying around let me know!

 

[jacob j.]

I'm pretty sure I got an extra crank Mr. N.

 

[Bigmac]

Port match the gem muffler and installed it,
It has a nice sound to it, and it seemed really open it up, throttle response is much better!

And even with the 50 inch bar and chain it’s really snappy, it seems quite a bit snappier than it did with the puck muffler

 

[Bigmac]

Got a chance to test the gym muffler, and as predicted it lost Touque, going to fab up some kind of restrictor/spark screen and see what happens

 

[Bigmac]

The adjustments I made to the chain definitely worked out, the chain feels really good, just the right amount a bite and chips size. But I’m gonna have to do something about the Oiler, it just isn’t up to it, It oils fine with an 8 pin or a shorter bar. Have the chain soaking wet here at the house, and in 4 cuts it was pretty dry.

 

[Lee H]

Sounds pretty good, What WB carb did you end up using.