Mcculloch sp125/101b kart saw build thread

[Bigmac]

Try to decide on the directions for this 101 with the wb, I have another 101b decal
But am thinking of going with the textured black recoil cover and that’s screaming mc101dI don’t have that decal but is it’s not expensive! Lol

any votes on this? I could go either way, the 101d is different and they cam from the factory with a black fan shroud, but it also wasn’t as common of a swap.

 

[Bigmac]

Did some more assembling and mock upI think I have the manifold close to where I want it, it’s a prototype and the likes 3 gasket under the intake, which means I can use 1/4 material for the base next time! That will be nice in the future, it’s manly to help clear the the chrome cover. I checked the line up with my mock up tank and it’s going to work out, I am considering making and adapting plate for the intake manifold junction into the air box, this would allow easier install and proper seal on the intake boot and better serviceability and it would be easier to make several.


I this block is ported, but surprisingly the port timing match’s my stock 101b motor with .004 bore, this is .060 over, so the angle on the port roof must have allowed for some port drop in the overbore! I was worried it would be radical, the transfers are squared on the roof but not raised, the opposite side is a perfect match and they kept the directional flow.They beveled the bottom of the transfer skirt and that will help this sloper breath a little better too!

 

[Bigmac]

I decided to put the tank off of my other saw to break in this 101 motor, Then I can have a direct comparison with the V4 reads and WB carburetor, also wanna make sure there’s no bugs in this motor before I hassle with a bunch of issues! LOL

So I’ve been doing some heat cycles today and getting the carburetor dialed in

 

[Bigmac]

Made a couple cuts, left it pretty rich for break-in, need to find some decent wood!

 

[Steve]

Made a couple cuts, left it pretty rich for break-in, need to find some decent wood!

Looks like you murdered a Christmas tree farm Nathan!

 

[Bigmac]

Looks like you murdered a Christmas tree farm Nathan!

Lmao! It dose! My dad had this super bushy odrimental tree, and half of it split off, so mac time! Lol I need to fine some decent wood!!

 

[jacob j.]

Nathan - I hope you're ok with me piggy-backing on your thread, but I wanted to post some interesting pictures of some kart stuff I got from a machinist years ago in Michigan.

It's an MC-6 engine, which he ran in the vintage class, 87cc. He made a full-circle crank, and it's a fully-welded, all metal full circle crank. I've not seen anything like this in any
Mac engine I've ever torn down -

 

[jacob j.]

He made his own "super stuffer," which is a cast and machined piece.

 

[jacob j.]

The block is where it really gets interesting - he filled a large part of the intake, all of the ninth port, and the rear transfer tunnels with Devcon.

He ran a BDC carb on methanol (on the sloper style intake manifold) through this engine and he said it was the fastest 87cc engine ever.

 

[jacob j.]

He made a home-made tri-channel boost port.

 

[jacob j.]

Even the flywheel is trick - the fins have been machined down about 3/8", and the back was shaved significantly. It's also been balanced - in the top of the first picture, you see where he drilled the
casting during balancing. In the second picture, you can see a broken area near the right center of the flywheel - he had a starter cup mounted there that broke off when he crashed his kart. This
flywheel weighs almost half of what a stock flywheel weighs.

 

[Frank bierce]

Some serious ingenuity in that MC-6 block!! Really cool stuff

 

[Bigmac]

That’s some cool stuff JJ! I like cool stuff and information! What are you going to do with it?

 

[jacob j.]

That’s some cool stuff JJ! I like cool stuff and information! What are you going to do with it?

I've got a Super 44 chassis that I'll put this in. I have a shot-peened & polished rod and an anodized Burris .020" over piston for this set-up. I have to send the
block in and get it bored. I'll run a Hovey dual-darb manifold on it. I haven't decided on carbs yet.

 

[Bigmac]

I've got a Super 44 chassis that I'll put this in. I have a shot-peened & polished rod and an anodized Burris .020" over piston for this set-up. I have to send the
block in and get it bored. I'll run a Hovey dual-darb manifold on it. I haven't decided on carbs yet.

Awesome! Can’t wait to see it!

 

[Bigmac]

I have made some progress on the wb, I am now happy with the carb mount and boot seal, just waiting now for my machinest to finish the adapter, I gave him a reminder text this weekend! Lol

Have the the motor running good with the sdc, starting and idling good, need to get some decent wood to test in, and eventually do the tank reed swap.

 

[Bigmac]

Got a teaser from my machinist today, says the adapters will be done tomorrow

 

[Bigmac]

So I got to look at the adapter, and it wasn’t perfect, I gave him my boot to finish it off, it needs a tiny bit more machining, and he only has a a 3 jaw, so he has to take it to work to finish it, I am super excited! It’s so close!

 

[sawfun]

So I got to look at the adapter, and it wasn’t perfect, I gave him my boot to finish it off, it needs a tiny bit more machining, and he only has a a 3 jaw, so he has to take it to work to finish it, I am super excited! It’s so close! View attachment 210580 View attachment 210581

I'm REALLY liking that work.

 

[Bigmac]

I'm REALLY liking that work.

Thanks, my machinest Is a good guy! I think version 2 on the manifold will be a little improvement over the prototype, but I am hoping the adapter is a winner! Getting excited to do some testing! Hoping it’s a good improvemen. The wb37 might be a decent compromise for the bdc, the bdc looks like about a 27mm venture and the wb37 is designed for a 150-200cc engine and has a 25 or 25.5 venture, I am going to test a smaller 24mm venture and see how it goes, will probably get a wb37 for testing too, there is a China knock off of the 37 now too so beware.