Mcculloch sp125/101b kart saw build thread

[Lee H]

If i get a chance later i will gage the 797 i just rebuilt

 

[Lee H]

Ok here it is, Fella's don't ever ask me to do comp test on one of these efin saws.
What a mofo it was. Saw came out from under me twice and upside down i went
on my arse and back. That hurt.

 

[jacob j.]

I went ahead and did two of my SP saws just now - one is a chrome-bore 125c and the other is a .020" over steel-sleeve saw. The steel sleeve saw got to just over 170 psi on ten pulls.

The chrome-bore saw got to 177-178psi in ten pulls. This was using a Lang Tools tester that I bought from @Guido Salvage. I figured the chrome bore saw would have more snap, as
it's more aggressive in the cut.

With the steel-sleeve motors, one factor is if they've been bored/honed, if the person doing the work scraped the squish band with the boring/honing mechanism.

 

[Lee H]

And mine has only made a couple cuts. It still needs to be broke it. Terry Ives told me it
takes some to get the rings to seal. I pull my arse off to get it to where it stopped.

 

[Scott Kelsey]

Guys, I have a question for you all. I remember reading some info in years past regarding NOT to bore cut with a roller nose. I do not know specifically why because I am not experienced with them, but is it because of the chain/driver gap where the bar transitions to the roller allowing the chain to come off the bar, or?

 

[heimannm]

Others will know more, but my experience with roller nose bars is that it is very easy to get a chip or sawdust in that gap and stop the chain dead. It can happen if you have the bar buried in a log as well.

Mark

 

[sawfun]

My understanding is that it is very hard on the tip. I've had rollernose bars buried in big wood and never had an issue bucking, then again, I may be just lucky. I have had a sprocket nose locked up with dust & pitch. Having a longer bar than necessary seemed to help with that for me.

 

[Bigmac]

I think the main issue is the roller had less stability and can’t take much abuse. No reason to push a rare bar, unless you got spares. 2-7/8 tips are harder to come by, will only buck with mine

 

[Scott Kelsey]

Thanks for the insight guys.

 

[Bigmac]

Thanks for the insight guys.

I have probably f’ed up some holy grail parts for some. So take my advice with a grain of salt

 

[heimannm]

This appeared recently.



It has a few problems.





I am in need of a boost port cover if anyone knows where I can find one, I have gaskets on hand.



I may just try to find enough pieces to put it together and put it in the display as a kart engine representing the 101 models. I have a pair of MC 10's and a MC6 in there already.



Mark

 

[Lee H]

I may have a boost port cover for you Mark. I will look later when i get home.

 

[jacob j.]

I may have a boost port cover for you Mark. I will look later when i get home.

If you don't Lee, I'm pretty sure I do.

 

[Lee H]

This appeared recently.

View attachment 325293

It has a few problems.

View attachment 325294

View attachment 325295

I am in need of a boost port cover if anyone knows where I can find one, I have gaskets on hand.

View attachment 325296

I may just try to find enough pieces to put it together and put it in the display as a kart engine representing the 101 models. I have a pair of MC 10's and a MC6 in there already.

View attachment 325297

Mark

I found a boost port cover Mark. I will get it in the mail tomorrow.

 

[heimannm]

Thanks Lee. I'll post some photos of another McKart/saw project that has come across my bench. This one has lived a hard life.

Mark

 

[heimannm]

 

[heimannm]

This one started out with a 101 engine that suffered catastrophic failure when the wrist pin slid over. I had a MC40 on hand so I put that in instead.



I ran it a few times, had a few problems, and eventually traded it with AWOL. He made it run very well, right up to the point the connecting rod came apart and started the major modifications. He filled in the third port, made an internal transfer and modded the piston to accommodate the changes and patched the crankcase back together. New transfer on the left, exhaust on the right.



Piston mods to take advantage of the new internal transfer.



The crankcase was badly damaged, AWOL had patched it and I took it a step further.



At some point during the major failure, the insert on the PTO side was knocked loose in the crankcase. I made a plate to install over the insert to hold it in place, at the same time I sealed the insert with LocTite 290 to maintain the integrity of the crankcase...for a while anyway.



I will try to get this one back together this week just to hear it run again. I have no delusions of it holding up for long, but I would like to make a few cuts with it before it detonates for good.

By the way, the MC40 has been bored oversize from 2.165 to 2.250 currently...that's about as far as can possibly go...MC75 piston in there now.

Mark

 

[Hinerman]

This one started out with a 101 engine that suffered catastrophic failure when the wrist pin slid over. I had a MC40 on hand so I put that in instead.

View attachment 326015

I ran it a few times, had a few problems, and eventually traded it with AWOL. He made it run very well, right up to the point the connecting rod came apart and started the major modifications. He filled in the third port, made an internal transfer and modded the piston to accommodate the changes and patched the crankcase back together. New transfer on the left, exhaust on the right.

View attachment 326018

Piston mods to take advantage of the new internal transfer.

View attachment 326020

The crankcase was badly damaged, AWOL had patched it and I took it a step further.

View attachment 326024

At some point during the major failure, the insert on the PTO side was knocked loose in the crankcase. I made a plate to install over the insert to hold it in place, at the same time I sealed the insert with LocTite 290 to maintain the integrity of the crankcase...for a while anyway.

View attachment 326026

I will try to get this one back together this week just to hear it run again. I have no delusions of it holding up for long, but I would like to make a few cuts with it before it detonates for good.

By the way, the MC40 has been bored oversize from 2.165 to 2.250 currently...that's about as far as can possibly go...MC75 piston in there now.

Mark

That thing was fast as s-word, and even louder than it was fast!!!!

 

[qurotro]

Gentleman, an odd question.
Why does the transfer holes has scratch marks on them?? 3 out of 6 holes on mine has hair-like scratch. Can be felt by pencil tip, along with a polished surface around that area. Does not look like dust ingestion to me.

 

[Bigmac]

Gentleman, an odd question.
Why does the transfer holes has scratch marks on them?? 3 out of 6 holes on mine has hair-like scratch. Can be felt by pencil tip, along with a polished surface around that area. Does not look like dust ingestion to me.

Can you post a pic?