Mcculloch sp125/101b kart saw build thread

[Lee H]

The 2 pictured are the same except the one on the right is for a geardrive like an 890 895
and the left one is a direct drive saw 790 795

 

[sawfun]

The 2 pictured are the same except the one on the right is for a geardrive like an 890 895
and the left one is a direct drive saw 790 795

That's what I was thinking as well as a fair amount of metal has to be filed off a geardrive stuffer for it to fit A 125 or 797 crankcase. Yhis is probably due to larger counterweight on a 123cc vs 103.

 

[Lee H]

It's the stroke, The counter wieghts look about the same. When i did my 797 geardrives
i had to use the 895 stuffer. Grind in where the rod swings through to clear the rod and
rod bolts. One i added a double gasket between stuffer and block.

 

[jacob j.]

I started on the .068" over 101 today:

 

[jacob j.]

Also weighed out some oversize kart pistons (with rings but not a wrist pin):

First, Burris .068" over 101AA style "Quicktime" type piston and rings:

 

[jacob j.]

Second up: .050" over Wiseco Mc-101 "Classic" piston and rings:

 

[jacob j.]

Third up, just for comparison sake - Standard McCulloch SP-125 piston with new standard rings:

 

[Bigmac]

It's the stroke, The counter wieghts look about the same. When i did my 797 geardrives
i had to use the 895 stuffer. Grind in where the rod swings through to clear the rod and
rod bolts. One i added a double gasket between stuffer and block.

Thanks for the info. I know I mocked up the stuffer on a 101, and it cleared but I also had a thick gasket, maybe I will try it with two gaskets or clearance it a bit, and see what it dose to the powerband.

 

[Bigmac]

I started on the .068" over 101 today:

Also weighed out some oversize kart pistons (with rings but not a wrist pin):

First, Burris .068" over 101AA style "Quicktime" type piston and rings:

Second up: .050" over Wiseco Mc-101 "Classic" piston and rings:

Third up, just for comparison sake - Standard McCulloch SP-125 piston with new standard rings:

Awesome! That’s a lot of difference in weight, I noticed on my oversized Burris pistons that the the inside casting is the same dimensions as a stock bore and the piston skirts just get thinker for the oversized pistons, that weigh adds up. Weisco still dose the on some of there forged pistons.

 

[jacob j.]

Awesome! That’s a lot of difference in weight, I noticed on my oversized Burris pistons that the the inside casting is the same dimensions as a stock bore and the piston skirts just get thinker for the oversized pistons, that weigh adds up. Weisco still dose the on some of there forged pistons.

I still think the pistons made by McCulloch back in the day are some of the best looking pistons I've seen. Even the pistons for the smaller saws were manufactured to a very high degree of precision.

Years ago I mike-ed out some SP-80/81 pistons I got in a lot of NOS parts and there was virtually no variance among several pistons in the same letter sizing groups.

 

[Bigmac]

Played with the wb101 and 797 with some .404, 8pin and the 50” bar basically buried and it didn’t have a problem pulling it even though some huge knots. I don’t think it’s any faster thou. May even be slower than the 9 pin 3/8, the square .404 was smooth, and the carlton .404 round grind is super ruff. My YouTube account got suspended for the wb video, so pictures will have to do for now

 

[Bigmac]

I clearances the 795 stuffer, it now fits without any contact, without a gasket. It didn’t take much, a little of the top an bottom and radius the sides of the main throw.

 

[jacob j.]

A little full-circle crank action for the Mc-91b five.five cube hotsaw:

 

[Bigmac]

A little full-circle crank action for the Mc-91b five.five cube hotsaw:

Suweeet! Can’t wait to see that run!

 

[Lee H]

Jacob, I had one of those. I sold it in a 101 chainsaw. It was built the same way. I got it from
Rich Dugan in a saw i bought from him years ago. Not sure if it made much difference.

 

[jacob j.]

Jacob, I had one of those. I sold it in a 101 chainsaw. It was built the same way. I got it from
Rich Dugan in a saw i bought from him years ago. Not sure if it made much difference.

Lee - I think it takes a particular carb-intake-stuffer-porting combo to really see the benefits. My plan with this is a Reed 246 vertical intake, a Go-Power six petal reed cage,
and an HL methanol carb. I have a GEM super stuffer for it as well.

 

[Bigmac]

Lee - I think it takes a particular carb-intake-stuffer-porting combo to really see the benefits. My plan with this is a Reed 246 vertical intake, a Go-Power six petal reed cage,
and an HL methanol carb. I have a GEM super stuffer for it as well.

That’s how I see it as well, and I think the smaller motors gain more from it too. It’s interesting how the hybrid 440/460 gain a bunch of rpm from the smaller case volume of the 440.

 

[Bigmac]

Jacob, I had one of those. I sold it in a 101 chainsaw. It was built the same way. I got it from
Rich Dugan in a saw i bought from him years ago. Not sure if it made much difference.

That’s interesting, i want to test the stuffer on my saw next to see what happens, I think it will raise the peak rpm. I ordered up the wb37 too, want to test it after that.

Your 123cc gear drives seem like they turn more rpm with the stuffer, but maybe I an hearing things!

 

[Lee H]

The last geardrive 797 i did is actually a super 797 with the sdc carb, I runs so good and strong.

Lee - I think it takes a particular carb-intake-stuffer-porting combo to really see the benefits. My plan with this is a Reed 246 vertical intake, a Go-Power six petal reed cage,
and an HL methanol carb. I have a GEM super stuffer for it as well.

If i remember right, That 101 i sold with the full circle crank didn't seem to have the power
other 101's i have. Not sure why.

 

[Bigmac]

Got the WB 37 today, got it modded up to fit, fired it up and got it relatively tuned. It is 28 mm bore, and a 1 inch VenturiGot the WB 37 today, got it modded up to fit, fired it up and got it relatively tuned. It is 28 mm bore, and a 1 inch Venturi