Mcculloch sp125/101b kart saw build thread

[dik650]

I read .750, but mine are more like .818 from one end to the other.
The rest of the measurements. Not using my favorite measuring tools at the moment..

Piston 2.2750"
bore 2.2814" with some variance
Rod 0.822"
Journal 0.630"
Needles 0.194

Not sure about the P2W clearance.

 

[jacob j.]

If your measurements are fairly accurate, then your piston may be on the loose side in the bore. I traditionally run mine .005-.0055",
depending on how far oversized the motor is. The kart guys run their motors a little looser mostly to get the higher RPM out of them,
but then they have much shorter service lives.

 

[dik650]

I've had it all the way apart. I trust my micrometers, but I've never been too sure about the dial bore gauge I'm using..
I believe someone's done a DIY hone job.
The bore wonders from 2.2814"- 2.2824" up & down & goes out of round about half as much.

There are some jagged edges around the upper transfers which would indicate a ball hone?



Little less excited than I was before, as this isn't congruent with the listing description.
I is not believing that to be el bore de factory..

 

[jacob j.]

I've never heard of anyone running a ball hone through an iron-liner bore, but anything is possible.

The marks look rougher than what I've seen a ball hone produce. They've scratched it up with something though.

It'd be easy enough to get that honed out for an oversize piston. I think Terry Ives has over sizes as small as .004".

 

[dik650]

Other non factory looking things, perhaps?
Some grinding, & some pecking on the roof of the transfers.

 

[dik650]

this is the best carb I recommend the hl324a with the shallow fuel inlet. It’s a good cheap upgrade

View attachment 374735


View attachment 374736View attachment 374737I ran into space issues with the 790 air box. The fuel inlet on my Chinese hl324 off of my Chinese 070.

I definitely need the low profile fuel inlet. Most of what I see is newer stuff without such inlet.

 

[dik650]

Little update.
The seller agreed to give $200 back for a rebore & piston assembly. Sounds good to me! Off go the pieces to California so Terry Ives can do his work.

What an awesome seller
I still can't get over how much work he put into packing the saw engine.