McCulloch Super Pro 125c build thread

[p61 western]

Good deal - everything on mine looks the same. Do you have everything you need to finish your build? I should have some extras left over here.

I think so, but if I need anything I'll ask you first JJ. I didn't plan on going the hot rod route, but Terry talked me into it lol.

 

[Steve]

I think so, but if I need anything I'll ask you first JJ. I didn't plan on going the hot rod route, but Terry talked me into it lol.

I bet your arm still hurts!

 

[p61 western]

I bet your arm still hurts!

Lol yeah it didn't take much lol. He really likes that particular cp block.

 

[Bigmac]

I bet your arm still hurts!

Ya it got twisted hard! He is a victim!

 

[p61 western]

Ya it got twisted hard! He is a victim!

Lol and you might have had something to do with it as well. Oh and yes poor me!!!

 

[Bigmac]

Lol and you might have had something to do with it as well. Oh and yes poor me!!!

Me....what me? Ok, so I didn’t tell you no! I am excited to see yours run! Terry has some go0d ideas, I love the boost port!

 

[p61 western]

Me....what me? Ok, so I didn’t tell you no! I am excited to see yours run! Terry has some go0d ideas, I love the boost port!

I need to get over there and drop off the rest of the parts he needs. Thank you again for that early block.

 

[sawfun]

It sounds like it might be best to go stock with the 125 without hacking the saw up. Maybe in the future gather and do a 101 build. What do you guys think?

I have a stock tank SDC 101b and a hacked tank BDC. I'd suggest going with the stock tank SDC carb for your first 101. A hacked tank, custom linkage is a ton of work and trouble if you try to keep it under the hood.

 

[jacob j.]

The 101b an the sp125 have reverse thread pto and no keyway, but are not the same crank, the 797 and mc101/101a/101aa had standard thread/key way pto’s, all are of these are interchangeable otherwise

I think one main difference between the 101b crank and the SP125 cranks is the bolt-on weights on the SP cranks. One of the kart guys I was talking said he used the saw crank once and the weights came off during a race and obliterated his engine.

 

[p61 western]

I think one main difference between the 101b crank and the SP125 cranks is the bolt-on weights on the SP cranks. One of the kart guys I was talking said he used the saw crank once and the weights came off during a race and obliterated his engine.

Yep Terry mentioned over a certain rpm bad things happen to the saw cranks lol. He actually had a busted up block there from the very thing your talking about.

 

[Bigmac]

I think one main difference between the 101b crank and the SP125 cranks is the bolt-on weights on the SP cranks. One of the kart guys I was talking said he used the saw crank once and the weights came off during a race and obliterated his engine.

I have seen counterweight come off a lot of 101 cranks, the welded ones are prone to failure as well, lee had a welded crank come apart in a 797/101 I believe. He felt it was from tapping the crank in place, idk, I think it’s a weak point for all the cranks. And kart use is way harder life than saws!

On another note on the rod bold, I know it been said that a standard grade 8 cap head will work in saw use, and it might in stock saws, in the kart days the first mc101’s came with cap head bolts had a massive failure rate, Mcculloch came up with the splined bolts to fix the issue, in saw use only the 125 got the splined bolts, the 797 got cap head bolts, the rpms in my mind are the killer, the saws don’t turn the rpms as the karts, and especially modified kart motors.

 

[jacob j.]

I made quite a bit of progress today - we were without power for the first part of the day so I was working by spotlight. I lapped the intake manifold and hand-cut a new intake gasket.

I put a thin layer of Loctite 518 on both sides. I also ensured that the intake manifold sits flush and that the reeds fit flat and even on the manifold.

 

[jacob j.]

I got the starter fixed up - it's an old 101 starter from one of the 101AA red, white, & blue engines. After setting the tension on the spool, I lubed it with PB Blaster "Dry" aerosol.

I set the mounting nuts in the shroud with Shoe-Goo. I think originally they used some sort of epoxy.

 

[jacob j.]

Next up, I go for mounting the bottom strap. It's part of the vibration isolation on the 125s, and the mount that's circled is the one that usually falls apart.

I've seen some re-pops made of those but I don't know who is behind that. I found NOS on ebay a few months ago.

 

[jacob j.]

I went ahead and installed the manifold, 1/4 shroud, and rear vibration mount. I line everything up for the rear vibration mount first and start the screws, then go back and start
the screws for everything else to ensure it all lines up.

 

[jacob j.]

Bottom strap installed - I leave the mount screws a little loose until I get the strap hooked to the tank - it's another one of those "lining it up" scenarios.

 

[jacob j.]

It's starting to come together - this saw got clobbered at some point and the cylinder shroud was caved in at two areas and bent pretty good. I was
able to straighten it out quite a bit with a small ball-peen hammer on a Maple stump. It's still not totally lined up - two of the mounting holes for the
starter are a little off, so I'll rectify that tomorrow.

 

[jacob j.]

Tomorrow: go through the carb, fit a new duckbill valve and o-ring to the fuel cap, pressure test the fuel line, and test fire the saw.

 

[p61 western]

Next up, I go for mounting the bottom strap. It's part of the vibration isolation on the 125s, and the mount that's circled is the one that usually falls apart.

I've seen some re-pops made of those but I don't know who is behind that. I found NOS on ebay a few months ago.

That's a part I need to track down. Mine is pretty worn out. It's looking great Jacob.

 

[jacob j.]

That's a part I need to track down. Mine is pretty worn out. It's looking great Jacob.

They're usually on ebay. I think I was searching for parts for a Super Pro 81 when I spotted it. It may have been Bryce that did the re-pops and was selling
them for $18 apiece.

It's coming together - this build was more for me to get familiar with the Macs again so I can build up the two old kartsaws and CP-125 that were my old man's.