Mcculloch sp125/101b kart saw build thread

[jacob j.]

Are those Terry's proprietary cap bolts? They look good.

 

[Bigmac]

Not going to lie, I was a little bummed when he said my rod was okay lol. Looks good glad to see you back at it.

Copy, he’s using the SP rod then, they are actually a pretty beefy rod, I have a few that are in really good shape! With the new rod, it must be a smidge taller than the stock rod that I had before, the piston is sitting up slightly out of the hole, which is fine for squish because of the head gasket that I use, and it will reduce some port timing, which I’m excited about I need to talk to him about that in the future if he can make the piston crown a little taller to give the saw more torque

 

[Bigmac]

Are those Terry's proprietary cap bolts? They look good.

Yes I believe so! I have been looking at then an they look nice! It’s the first time I’ve seen them, he has sent a few different rod bolts over the years but these look different

 

[Bigmac]

I use a degree wheel to check the points, they are set at 27 degrees btdc and that is .018 points gap, have seen some variations had one that was 22 degrees at .018!
Also check the port timing it was 94/118 or total duration numbers are 183/127 and this is stock port 101b block

 

[Bigmac]

Got the head and flywheel on, the nos Stars and Stripes recoil came with new stater paws and springs so I installed them on this

 

[jacob j.]

Does Terry have new copper ring head gaskets? I need to get a couple-three of those.

 

[Bigmac]

Does Terry have new copper ring head gaskets? I need to get a couple-three of those.

Yes sir, he makes them! He has some different thicknesses too

On Mac engine parts my rule is now ask Terry first!
I have only seen one head gasket on eBay in the last 5 years, I think they are about $20 each now from terry

 

[Bigmac]

For those who haven’t done the conversion the stock saw manifold needs to be trimmed
And a hole needs to be drilled and taped to mount the kart shroud along with spacers.

Here is a trimmed manifold next to a stocker, you can see the upper left threaded hole on the left manifold, that’s to mount the kart shroud, I radiused all the sharp edges inside the stock manifold for better flow, I might take a stock manifold and add a lager hole with the appropriate flange for the larger boot and wb swap to test against the v4 kart reeds.
Installed nos reeds and used red lock tight on the bolts

I made a little bit of a relief for the retainer in the block for the head bolt,

Here is some comparison pics, the stock manifold is 20.5 mm and the wb is 25 mm

 

[Willard]

Yes I believe so! I have been looking at then an they look nice! It’s the first time I’ve seen them, he has sent a few different rod bolts over the years but these look different

Those look like aerospace grade titanium tapered head bolts. Half the weight and stronger then most steel.
I'm using them in my bikesaw build.

 

[Willard]

I'm swapping out my crankcase bolts with these M6 titanium.
The button heads will hold the sideplates to the crankcase.

 

[Bigmac]

I'm swapping out my crankcase bolts with these M6 titanium.
The button heads will hold the sideplates to the crankcase.
View attachment 201760 View attachment 201761

That’s cool, I am not sure on these, I will have to ask Terry, I checked them with a magnet and it’s not as strong of a pull as the steel, is your ti magnetic? Ti isn’t suppose to be magnetic, so I am doubtful

 

[Willard]

Don't

That’s cool, I am not sure on these, I will have to ask Terry, I checked them with a magnet and it’s not as strong of a pull as the steel, is your ti magnetic? Ti isn’t suppose to be magnetic, so I am doubtful

I just went out to the shed and tried picking up one of the bolts with a 066 flywheel magnet. The magnet couldn't pick up the 6mm cap screw bolt but moved it a wee little bit.
Pure titanium is not magnetic but different alloys are needed to make it strong, some alloys like cobalt are magnetic.
Acer Racing where I bought mine from have a warning that not all titanium fasteners are the same. They say some of the Chinese fasteners are low grade around grade 2. They sell grade 5 to 6 what I got.
I'm sure yours are titanium even if weak magnetically.

 

[Al Smith]

FWIW those cut down cap screw rod bolt are similar to what I did with grade 8 Holo-chrome brand except I left a flange on the bottom .As a rule on a grade 8 the head portion is not as hard as the shaft ,use carbide though or ceramic because it's still harder than mild steel or grade 5's .I've drilled the heads off of 3/4" grade 8's on a brush chipper but it takes solid carbide .

 

[Al Smith]

This would not apply to most people .Firstly because not too many people will ever delve into Mac engines that used spline bolts .It might to a few others .If you rework say a grade 8 socket head because you can in essence deform the socket it would be my suggestion the replacement rod bolts only be used once .If they get deformed badly enough the only option left is to drill off the heads which would be a pain in the buttocks to put it lightly .

 

[Willard]

Reason why the tapered head cap bolts Bigmac has reminds me of some titanium ones I've found, captive washers included.

 

[drf256]

Amazing thread. Great reference for people doing this build.

Thank you for taking the time to chronicle this.

 

[Bigmac]

Put the oil tank and stuffer on, installed a nos oil line and pickup. I use bulk, ten pack stuffer gaskets for the 101, they are super cheap that way, but they don’t have a manual Oiler hole, so I cut that in, the oil tank gasket I cut out myself, they are available, but also aren’t hard to make
This is the manual Oiler piston, a light coat of oil before install
On the 101 block, you need to drill out the block for the av limiter, 5/16 drill bit

 

[Bigmac]

The 101 blocks don’t have a hole for the manual Oiler. I use the stuffer or gasket to locate, a 1/4 hole all the way through and a 15/64 is the drill size for the seal. Some blocks have different size “boss” for the pto side bearing, you can extend the 1/4 hole to relieve the area need for the manual Oiler pushrod or use a rotary file
Here is the factory 125
Here is a stock 101aa block
And the bottom of a cp125

 

[Bigmac]

Here is another 101aa block with a lager boss, it’s a much lager relief, I used the rotary file

 

[sawfun]

The 101 blocks don’t have a hole for the manual Oiler. I use the stuffer or gasket to locate, a 1/4 hole all the way through and a 15/64 is the drill size for the seal. Some blocks have different size “boss” for the pto side bearing, you can extend the 1/4 hole to relieve the area need for the manual Oiler pushrod or use a rotary file View attachment 202476
Here is the factory 125View attachment 202477
Here is a stock 101aa block View attachment 202478
And the bottom of a cp125View attachment 202479View attachment 202480

Been there, done that a couple of times. That was probably the only issue with the kart to saw conversion.