Mcculloch sp125/101b kart saw build thread

[jacob j.]

Now you guys get two -

 

[Frank bierce]

Now you guys get two -

Such sweet music!!

 

[Woodslasher]

Now you guys get two -

Yer a brave man for leaving the clutch cover off....

 

[jacob j.]

Yer a brave man for leaving the clutch cover off....

Not really. The Mac clutches have an external retaining nut.

I use those large Homelite and Stihl clutch washers though in case the clutch comes apart, it won't wipe out the clutch cover.

There's a couple of Homelite washers that work the best because they're a close fit to the Mac clutch drum.

 

[northwest saws]

Now you guys get two -

For a second there I thought I heard the intro to "Hot for Teacher" by VanHalen.

Sent from my SM-N970U using Tapatalk

 

[Lee H]

Has anyone tried the Little Red Barn 125 piston, Mac part # 85539 i see them on ebay.
Not that i'm looking just curious.

 

[Steve]

Has anyone tried the Little Red Barn 125 piston, Mac part # 85539 i see them on ebay.
Not that i'm looking just curious.

If it's like the piston I got for my 4200 I would not unless it was my last resort. The casting was bulky and the machining was sloppy.

 

[Bigmac]

Has anyone tried the Little Red Barn 125 piston, Mac part # 85539 i see them on ebay.
Not that i'm looking just curious.

We had a discussion on the 125C thread, I don’t think it will run, or if it does it won’t run well, it doesn’t have a keeper for the SP Circlip, It also has a hole that would flow transfer port volume out the exhaust port, it also looks like it’s set up for needle bearings in the piston, I’m not sure what the story is on it!

 

[Lee H]

Good answers and a piston to stay away from.

 

[Bigmac]

Going to start playing again

 

[Lee H]

Holy 101 and one SP, Very nice

 

[Lee H]

Actually, i'm thinking the block on the right is a CP block. Looks like the
coil mount is for the 3 leg coil. Correct me if my eyes are wrong.

 

[Bigmac]

Actually, i'm thinking the block on the right is a CP block. Looks like the
coil mount is for the 3 leg coil. Correct me if my eyes are wrong.

You are correct, cp block. Did the boost port mod to that block, hopefully she is a runner!

 

[Scott Kelsey]

Guys correct me if I am wrong, but the SP125's do not have boost ports right? Why do you think Mcculloch got away from them?

 

[Bigmac]

Guys correct me if I am wrong, but the SP125's do not have boost ports right? Why do you think Mcculloch got away from them?

The standard 797 is the only boost port saw, maybe a few super 797 as well. The super 797 and early cp125 had the boss for the boost port. I think they deleted it just because it was just one less part to fail, and the small gain in a saw wasn’t worth the trouble. Just a guess. And with a fixed head they couldn’t machine them in like the kart 101. The mc101 had the same boost port window as the 797, and could easily machined in the fixed head saws, but once they switched to the double hump boost port, they changed the casting entirely for the sp125.

 

[Bigmac]

One of these days I would like to find an early mc101, I think it should have the lowest port timing, should be a good saw motor.

 

[Lee H]

One of these days I would like to find an early mc101, I think it should have the lowest port timing, should be a good saw motor.

I sold one last year. I have a few 101B, MC saws and didn't really need it.

 

[Al Smith]

I may be mistaken on this but from my perspective the " boost " ports were just an attempt of better scavenging on the area about the intake side .Others might be sweeps, secondaries , finger ports or externals .Which might be a better option I really don't know .
My only attempt on the subject so far has been sweeped transfers using a raised dome piston but it seems to have worked out well .However that was on a Stihl 038 Mag ,I've never done anything like that on a McCulloch --so far .
It gets rather confusing at times .You've got a raising pressure following a decreasing pressure happening in milliseconds .You've got to let it out while you stuff it in at the same time and you don't have much time to do it .

 

[Bigmac]

Got the new transverse creek intake boots the the 125 today! Thanks @Duke Thieroff
The rubber quality seems excellent and is soft and elastic, have a few nos boots in the stash, and these seem to be much better!

 

[jacob j.]

I got mine today as well - I have two older SPs that I rebuilt a couple years that are getting new boots.