McCulloch Super Pro 125c build thread

jacob j. · Sep 16, 2019

A few other pictures - Mike, this picture shows that Mac shoebox saw coil on an SP block - I know it's a non-limited, electronic coil. I'm not sure if my dad swapped
the laminates out or not, so I'll investigate that. I know McBob did something similar with a Poulan coil.

jacob j. · Sep 16, 2019

These two pictures show the CP engine in the SP frame - you can see the horizontal-leg coil and the DSP-style compression release port. It's a stock bore cylinder as far as I know. My dad bought the cylinder new as a replacement part - it has no ID numbers and is not a boost port block.

jacob j. · Sep 16, 2019

These three pictures show where Rich welded the vibration mounts into the 101 head. He also trimmed the 101 head fins to fit the curved SP style cylinder shroud.

p61 western · Sep 16, 2019

jacob j. said:
A few other pictures - Mike, this picture shows that Mac shoebox saw coil on an SP block - I know it's a non-limited, electronic coil. I'm not sure if my dad swapped
the laminates out or not, so I'll investigate that. I know McBob did something similar with a Poulan coil.

jacob j. said:
These two pictures show the CP engine in the SP frame - you can see the horizontal-leg coil and the DSP-style compression release port. It's a stock bore cylinder as far as I know.

Thank you for the pics Jacob. How soon do you think you will start on your dads saw?

jacob j. · Sep 16, 2019

A couple of SP engines I rebuilt years ago - both are steel-sleeve blocks. The one on the left is a stock bore and the one on the right is .030" over.

Bigmac · Sep 16, 2019

jacob j. said:
These three pictures show where Rich welded the vibration mounts into the 101 head. He also trimmed the 101 head fins to fit the curved SP style cylinder shroud.

That’s cool! And even has the 125 bolt on counterweight crank

Bigmac · Sep 16, 2019

jacob j. said:
That's what it is running now and it's doing pretty good so far, but I think I can get more out of it and keep it under the lid...

A couple more notes - I was able to get new O-rings (1 7/8" x 1/8") for the fuel cap from the hardware store. For a duckbill valve,
I used a valve from a Stihl brush cutter that goes inside the tank vent. I'll find the Stihl part number for it. The rim of the opening to
the tank is pretty rough from moisture damage, so I'll lightly block sand that later to make it even.

How much bigger are the other carbs? They look like 19mm venture

Bigmac · Sep 16, 2019

jacob j. said:
These two pictures show the CP engine in the SP frame - you can see the horizontal-leg coil and the DSP-style compression release port. It's a stock bore cylinder as far as I know. My dad bought the cylinder new as a replacement part - it has no ID numbers and is not a boost port block.

Dose that cp block have the 101 bumps for the boost port area?

jacob j. · Sep 16, 2019

p61 western said:
Thank you for the pics Jacob. How soon do you think you will start on your dads saw?

I have a 394, a 346, and a Dolmar 120si to build for members here and then I'll launch into my old man's three saws. I'll do that CP conversion saw first, so we can see how
that all goes together.

Bigmac said:
That’s cool! And even has the 125 bolt on counterweight crank

My dad said it was really smooth - it was his favorite saw of the all. I chipped off about five pounds of old-growth Douglas fir sawdust and pitch from the engine. He
ran a 60" bar on it.

Bigmac said:
How much bigger are the other carbs? They look like 19mm venture

I think so, probably not much of a gain over the SDC-20. I have some of the fixed high jet carbs here to try also.

jacob j. · Sep 16, 2019

Bigmac said:
Dose that cp block have the 101 bumps for the boost port area?

No sir, which leads me to believe it was just a generic replacement block purchased as a stand-alone.

Bigmac · Sep 16, 2019

jacob j. said:
I have a 394, a 346, and a Dolmar 120si to build for members here and then I'll launch into my old man's three saws. I'll do that CP conversion saw first, so we can see how
that all goes together.

My dad said it was really smooth - it was his favorite saw of the all. I chipped off about five pounds of old-growth Douglas fir sawdust and pitch from the engine. He
ran a 60" bar on it.

I think so, probably not much of a gain over the SDC-20. I have some of the fixed high jet carbs here to try also.

That’s cool history! I have 2 original 101b blocks that were original saw converted, both stock bore and covered in pitch chips and oil! They smelled amazing! Lol
Ya I don’t think there will be much gain in any bolt on carb, the tank and intake manifold are right about 20mm so it could gain a tad if you find I 20mm venture.
I am working on a 1” bore, 24mm conversion that will take some grinding but will fit, also trying to get the v4 reeds in, my buddy has been busy and doesn’t have the manifold welded yet

jacob j. · Sep 16, 2019

Bigmac said:
I am working on a 1” bore, 24mm conversion that will take some grinding but will fit, also trying to get the v4 reeds in, my buddy has been busy and doesn’t have the manifold welded yet.

Awesome - I'm really interested to see how that turns out. I have a tank that is heavily corroded in the air box area so I'm going to cut all that out and go with the Reed 458 sloper manifold with the
6 petal reed cage and probably an HL-360A or similar.

Jay Hansen · Sep 17, 2019

jacob j. said:
We can meet up in Roseburg soon if you like, Jay.

Well, the saw is complete and a runner, but needs a few things touched up: The current clutch is pretty well worn out, but I've got a new replacement (somewhere), and the
air filter needs replaced but is functional. I need to swap the handle out for a better one later (this one has been clobbered and has a saw cut in the top, but is working).

That'd be great JJ. I just got back from the midwest, stopped and saw Mark and he answered a few of my questions. Let me know what works for you. I've got a few handles that are not perfect but ok, want me to bring a couple along?

jacob j. · Sep 17, 2019

Jay Hansen said:
That'd be great JJ. I just got back from the midwest, stopped and saw Mark and he answered a few of my questions. Let me know what works for you. I've got a few handles that are not perfect but ok, want me to bring a couple along?

That sounds great Jay - I'll send you a text.

PogoInTheWoods · Sep 17, 2019

jacob j. said:
For a duckbill valve,
I used a valve from a Stihl brush cutter that goes inside the tank vent. I'll find the Stihl part number for it.

The common Stihl duckbill is 0747-313-6810 ($.99) for their cheap little saws but there may be a different one for brush cutter applications (or a housing with a hose around the same duckbill having a different part number for the 'assembly'). Whichever, it looks like a good fit in that cap.

Al Smith · Sep 17, 2019

The only comment I'll make is I've seen vid clips of supposed 101's in 125 dress .They didn't run any better than a stock 125 .Which leads me to believe they ran a saw carb on it which is not nearly large enough to get the full potential of that engine . It takes fuel to make power .

sawfun · Sep 17, 2019

Al Smith said:
The only comment I'll make is I've seen vid clips of supposed 101's in 125 dress .They didn't run any better than a stock 125 .Which leads me to believe they ran a saw carb on it which is not nearly large enough to get the full potential of that engine . It takes fuel to make power .

My small SDC20 101b is a ton stronger than my sp125c. I believe the small carb robs torque in bar lengths over 36", however 36" and under, the 101b IS much stronger.

Bigmac · Sep 17, 2019

sawfun said:
My small SDC20 101b is a ton stronger than my sp125c. I believe the small carb robs torque in bar lengths over 36", however 36" and under, the 101b IS much stronger.

I agree, my 101 wants to rev but it feels like a shot bar saw, it feels like it wants to make power power higher but is choked up, and in smaller wood the extra rpm cuts better, but it doesn’t have the torque to pull a long bar, it wants to drop out of the power curve. Where as the 125 chugs down better. The sdc20 is basically a 70cc carb, I wonder how much the 125 would gain with a bigger carb alone, and how much better reeds would gain on an otherwise stock 125, I remember reading mcbob had put a sloper and bigger carb on a stock 125c and it was a runner! I really want to do some testing in the future with the wb setup on a stock 125 and 101s, super curious to the results!

sawfun · Sep 18, 2019

Bigmac said:
I agree, my 101 wants to rev but it feels like a shot bar saw, it feels like it wants to make power power higher but is choked up, and in smaller wood the extra rpm cuts better, but it doesn’t have the torque to pull a long bar, it wants to drop out of the power curve. Where as the 125 chugs down better. The sdc20 is basically a 70cc carb, I wonder how much the 125 would gain with a bigger carb alone, and how much better reeds would gain on an otherwise stock 125, I remember reading mcbob had put a sloper and bigger carb on a stock 125c and it was a runner! I really want to do some testing in the future with the wb setup on a stock 125 and 101s, super curious to the results!

I'm curious as well as I have a new WB that was bought for just that purpose. I can tell you a BDC under the hood is somewhat problematic. I need to get the needle lever spring set correctly again. But doing anything on that carb requires taking half the saw apart.

Bigmac · Sep 18, 2019

sawfun said:
I'm curious as well as I have a new WB that was bought for just that purpose. I can tell you a BDC under the hood is somewhat problematic. I need to get the needle lever spring set correctly again. But doing anything on that carb requires taking half the saw apart.

Have heard the bdc is a pain, the wb should be easier to tune if nothing else! Is the bdc flange below the air box?

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