MCCULLOCH The official McCulloch thread

[Woodslasher]

I found a 90570A complete assembly but the IPL calls out the same number with a B. I wonder if they are interchangeable ?

The actual cover looks exactly like mine so I'd guess it's the same. Don't take my word for it though. Here's a sold ebay listing showing the cover, if that helps any.

 

[Mac131]

Yep, that's exactly what I have found. I'll order one up! Thanks everyone!

 

[Definitive Dave]

I have a few mac centric questions for the experts as I try to get back to my big boy saw projects.
Will an MC91 and 795 fan cover interchange?
Are there any tricks or preferred methods to removing the clutch and flywheel from a 795?
As I move forward on the MAC obsessive journey are there any tools I should grab for working on the larger saws?
I am currently completely tearing down the 795, I really like the looks of it over a 125 honestly.
I want to make sure I am familiar with what is involved before stripping down the NOS 101B on camera

Current build plan - mostly 795 chassis, full wrap, all custom powder coating with three inter-changeable air filter covers, bored, ported 125 cylinder at 61.5mm bore, nikasil platted with Wiseco 61.5mm CCCR piston, billet full circle turbo crank stroked 4mm, V12 intake with Tillotson billet race carb (model as yet undecided), lightened flywheel (no fins), leveling kickstand, dual decomps, no dogs , left hand start, clearanced clutch cover to fit 15 or 16 pin rim, CCC Racing by Cannon custom racing bar with 72DL square 3/8" .050 chain, upright spring mounted pipe, woven custom rear and recoil handles, and a few surprises

It won't be done quickly, but it should reach the finish line in no time flat.
Dave

 

[Mac131]

The actual cover looks exactly like mine so I'd guess it's the same. Don't take my word for it though. Here's a sold ebay listing showing the cover, if that helps any.
View attachment 289086

So, I received my chain brake assembly the other day and the bar adjuster is on the cover...the power mac 6 adjuster is part of the oil tank. Not sure where the outer bar spacer would go either. Am I missing something here?

 

[fossil]

Geez Dave, don't go all out or anything.

Sounds like it will be quite the machine.

 

[Mac131]

Well turns out my first ported 10-10 cylinder had an extra 10+ thousands sidewall to piston skirt clearance and would hardly run for more than 10 seconds at a time...I inherited it this way. Fuel and air spitting back out the carb...not good. Ported a different head and fired it up today...sounds good! Going to idle a tank through her and compare it to a couple of my other 10-10s in some wood soon!

 

[Mac131]

I have a few mac centric questions for the experts as I try to get back to my big boy saw projects.
Will an MC91 and 795 fan cover interchange?
Are there any tricks or preferred methods to removing the clutch and flywheel from a 795?
As I move forward on the MAC obsessive journey are there any tools I should grab for working on the larger saws?
I am currently completely tearing down the 795, I really like the looks of it over a 125 honestly.
I want to make sure I am familiar with what is involved before stripping down the NOS 101B on camera

Current build plan - mostly 795 chassis, full wrap, all custom powder coating with three inter-changeable air filter covers, bored, ported 125 cylinder at 61.5mm bore, nikasil platted with Wiseco 61.5mm CCCR piston, billet full circle turbo crank stroked 4mm, V12 intake with Tillotson billet race carb (model as yet undecided), lightened flywheel (no fins), leveling kickstand, dual decomps, no dogs , left hand start, clearanced clutch cover to fit 15 or 16 pin rim, CCC Racing by Cannon custom racing bar with 72DL square 3/8" .050 chain, upright spring mounted pipe, woven custom rear and recoil handles, and a few surprises

It won't be done quickly, but it should reach the finish line in no time flat.
Dave

Sounds serious! Is it strictly a cookie cutter saw?

 

[jacob j.]

Dave -

The Mc91 and 91b use a different fan housing/cylinder shroud than the 790/795/895. This is what the 795 fan housing looks like:



This is what the Mc91/91b cylinder shroud and fan housing look like




The clutch and flywheel can removed with a steering wheel puller, assorted long SAE bolts, and some Stihl bar nuts to keep the long bolts in place on the puller.

I think the threads on the flywheel are 1/4-20 and the threads on the clutch are 10-24. Mark Heimann can verify.

The 795 is an easier chassis to shoehorn a kart motor into because you don't have to modify the head. If you want to shoehorn a kart motor into the SP chassis,
you have to make a provision for the rear vibration mount to fasten to the head and you may have to do some shaping of the cooling fins, depending on which shroud you want to use.

 

[Lee H]

I have a few mac centric questions for the experts as I try to get back to my big boy saw projects.
Will an MC91 and 795 fan cover interchange?
Are there any tricks or preferred methods to removing the clutch and flywheel from a 795?
As I move forward on the MAC obsessive journey are there any tools I should grab for working on the larger saws?
I am currently completely tearing down the 795, I really like the looks of it over a 125 honestly.
I want to make sure I am familiar with what is involved before stripping down the NOS 101B on camera

Current build plan - mostly 795 chassis, full wrap, all custom powder coating with three inter-changeable air filter covers, bored, ported 125 cylinder at 61.5mm bore, nikasil platted with Wiseco 61.5mm CCCR piston, billet full circle turbo crank stroked 4mm, V12 intake with Tillotson billet race carb (model as yet undecided), lightened flywheel (no fins), leveling kickstand, dual decomps, no dogs , left hand start, clearanced clutch cover to fit 15 or 16 pin rim, CCC Racing by Cannon custom racing bar with 72DL square 3/8" .050 chain, upright spring mounted pipe, woven custom rear and recoil handles, and a few surprises

It won't be done quickly, but it should reach the finish line in no time flat.
Dave

As Jacob stated the MC91 fan housing will not fit. The 91 is not a super series motor like the 795, 797 and 125 are.
Why are you using a 125 block instead of the 101B block that has the removable head. As for tools i made my own
that works for Mac flywheels, Mac clutches and Homelite flywheels like the 2100 models.

And where did you find that crank.

Good luck on your build, Sounds impressive.

 

[merc_man]

My mini is alive again. Made a homemade starter assy for it this past week.

Sent from my SM-G950W using Tapatalk

 

[heimannm]

Dave - You may want to look for one of these - McCulloch used some special cap screws for the connecting rod bolts on many of the 123 cc engines.

CRANK CAP SCREW TOOL SOCKET McCULLOCH CHAINSAW 125 SP125 101 KART 85583 BOXUP649 | eBay

Some of the saws use a piston with a blind end so it takes a special puller to extract the wrist pin. I think Duke's kit could be made to work but you would have to make some kind clip to put on the blind end to pull the pin.

The bearings normally stay on the crankshaft so a bearing separator is handy to have.

14pcs Bearing Separator Puller Set 2" & 3" Splitters Bearing Remover Service Kit | eBay

As JJ noted, the threads in the flywheel are 1/4-20, it is a good idea to leave the nut on the crankshaft (backed off a few turns) with using a puller as the flywheels will occasionally become UFOs when they pop off. There are also two 1/4-20 tapped holes in the crankcase cover to facilitate opening the crankcase.



I was thinking the tapped holes in the clutch were 8-32 but I cannot confirm or deny that.

Mark

 

[Woodslasher]

So, I received my chain brake assembly the other day and the bar adjuster is on the cover...the power mac 6 adjuster is part of the oil tank. Not sure where the outer bar spacer would go either. Am I missing something here?

Hmm, I'd swear my tensioner is on the cover, and despite the fact that my saw is wearing a (the original?) Mac b/c it is completely devoid of any bar plates.

 

[heimannm]

The older PM6 saws had the adjuster in the oil tank. Later ones, with a brake, had the adjuster in the clutch cover. You can use either one (but only one) if you put the later clutch cover on an earlier saw.

In fact, the oil tank on the later saws could not even be modified to accept the adjusting screw as they changed the design of the casting.

Mark

 

[Mac131]

The older PM6 saws had the adjuster in the oil tank. Later ones, with a brake, had the adjuster in the clutch cover. You can use either one (but only one) if you put the later clutch cover on an earlier saw.

In fact, the oil tank on the later saws could not even be modified to accept the adjusting screw as they changed the design of the casting.

Mark

Thanks Mark! Good to know. I have a question about a 2-10. Would you happen to know the year serial number 12-138042 was built. I went to acres site and it gives a couple year range. I was just wondering if anyone can narrow it down further.

Thanks!

Jeff

 

[Bigmac]

I have a few mac centric questions for the experts as I try to get back to my big boy saw projects.
Will an MC91 and 795 fan cover interchange?
Are there any tricks or preferred methods to removing the clutch and flywheel from a 795?
As I move forward on the MAC obsessive journey are there any tools I should grab for working on the larger saws?
I am currently completely tearing down the 795, I really like the looks of it over a 125 honestly.
I want to make sure I am familiar with what is involved before stripping down the NOS 101B on camera

Current build plan - mostly 795 chassis, full wrap, all custom powder coating with three inter-changeable air filter covers, bored, ported 125 cylinder at 61.5mm bore, nikasil platted with Wiseco 61.5mm CCCR piston, billet full circle turbo crank stroked 4mm, V12 intake with Tillotson billet race carb (model as yet undecided), lightened flywheel (no fins), leveling kickstand, dual decomps, no dogs , left hand start, clearanced clutch cover to fit 15 or 16 pin rim, CCC Racing by Cannon custom racing bar with 72DL square 3/8" .050 chain, upright spring mounted pipe, woven custom rear and recoil handles, and a few surprises

It won't be done quickly, but it should reach the finish line in no time flat.
Dave

Cool build! 150cc! Nice, the Stroker crank Will really wake up the 125, and allow you to set up a good squish, like that! Where did you get the crank?

 

[Al Smith]

As JJ noted, the threads in the flywheel are 1/4-20, it is a good idea to leave the nut on the crankshaft (backed off a few turns) with using a puller as the flywheels will occasionally become UFOs when they pop off. There are also two 1/4-20 tapped holes in the crankcase cover to facilitate opening the crankcase.


Mark

They are supposed to be 1/4" 20 .However for whatever reason on one of mine they were #12 -24 I think .They obviously would not hold and I tapped them out to 5/16" -18 .Let me just say pulling a flywheel from a 125 is not all that easy . If I ever need to pull another I'll heat the flange first .
Those splined screws for the rod were somebodies really brilliant idea--not .Before I had a splined tool I had an old Mac dealer loosen them for me and I cut down the head size on grade 8 #10 -32 by 5/8" screws so they had the clearance for the stuffer . I left a flange on the screw head just like the splined screws . A low head cap screw will not work and a button head is one hex wrench smaller and you'll strip it out before you get it tight .
I might be incorrect but I figured a grade 8 is a grade 8 weather it's Hollow-Chrome brand or McCulloch .

 

[heimannm]

Jeff - Best I can do is between 1969 and 1974 with the 12- prefix. My guess is closer to 1974 based on the high serial number.

Mark

 

[Mac131]

Jeff - Best I can do is between 1969 and 1974 with the 12- prefix. My guess is closer to 1974 based on the high serial number.

Mark

Roger that. Thank you!

 

[fossil]

I am posting these publications guides up for McCulloch saws which can help narrow some production dates. Handy to have for reference.

The best one I've found is the 1979 version. I have a 1972 version and a 1998 version. The 1998 version has some errors.

The 1979 version would put a 12- 2-10A 6/67 to 6/68.

If anyone has other guides, it would be good to get copies of those.

 

[PogoInTheWoods]

And depending on the saw and carburetor, there are date stamps on carb bodies that can also assist in some cases. The problem there could be older shelf stock on newer saws, but it is yet another indicator for at least ballparking DOM.