McCulloch Chain Saws

[heimannm]

I was moving the 70 cc cylinder to the new shop today and thought I'd look into the apparent discrepancies of the cylinder/crankcase assemblies with the impulse nipple (anti-vibe saws) and the front handle mounts (rigid mount saws).

Look what I found in my photos.







I should have remembered that the CP models use the rigid handle mount as an anchor for the lower/front anti-vibe mounts.



I expect you could plug the impulse port and use these for a rigid mount saw as well...?

Mark

 

[vinnywv]

Thats really cool. Great clarification.

 

[Jethro 2t sniffer]

I was moving the 70 cc cylinder to the new shop today and thought I'd look into the apparent discrepancies of the cylinder/crankcase assemblies with the impulse nipple (anti-vibe saws) and the front handle mounts (rigid mount saws).

Look what I found in my photos.

View attachment 801831

View attachment 801832

View attachment 801834

I should have remembered that the CP models use the rigid handle mount as an anchor for the lower/front anti-vibe mounts.

View attachment 801833

I expect you could plug the impulse port and use these for a rigid mount saw as well...?

Mark

Mark somewhere I've seen a picture from you of a CP80 what was that about? I've never seen or read it mentioned anywhere else since. Was it setup the same as the cp70? And the Cp70L is that also the same?

Really starting to get my head around the AV saws after getting another 1.

Was talking to Vinny and noticed the strange oil pump from the SP saws so he learned me about those lol

 

[PogoInTheWoods]

So the frustration factor evidently follows this saw. I still think the theory is right..., just not the piston I thought would be the ticket. Back to the drawing board on the compatibility prospects for a full skirt solution. Maybe a 69030 would have been the right choice for this particular rod/pin combination? Maybe just a rod swap with a smaller small end and different stroke for the 69412 is a possibility? Gotta be a combination that'll work short of a whole later style piston and cylinder..., which would defeat the purpose entirely anyway, now wouldn't it? LOL
Back to the IPL's....

One thing I did discover after tearing it down were some excessively worn rings that would not have made much compression. The cylinder has seen better days too, but isn't nearly as rough as it looks in the pic. More streaks than gouging. Some Scotch-Brite Red should restore a real nice finish with some time and patience. A project for another day at this point. At least we now have a good pic of the three finger transfers, eh?

​

 

[Jethro 2t sniffer]

So the frustration factor evidently follows this saw. I still think the theory is right..., just not the piston I thought would be the ticket. Back to the drawing board on the compatibility prospects for a full skirt solution. Maybe a 69030 would have been the right choice for this particular rod/pin combination? Maybe just a rod swap with a smaller small end and different stroke for the 69412 is a possibility? Gotta be a combination that'll work short of a whole later style piston and cylinder..., which would defeat the purpose entirely anyway, now wouldn't it? LOL
Back to the IPL's....

One thing I did discover after tearing it down were some excessively worn rings that would not have made much compression. The cylinder has seen better days too, but isn't nearly as rough as it looks in the pic. More streaks than gouging. Some Scotch-Brite Red should restore a real nice finish with some time and patience. A project for another day at this point. At least we now have a good pic of the three finger transfers, eh?

View attachment 801888​

So it doesn't fit the rod? Hit Vinny up for that piston he pulled out of that 6-10 and re ring the basterd lol

What a nightmare saw

 

[vinnywv]

Good grief charlie brown!!! So what piston did you get for it? I tried to find that info but the pages add up very quickly.

 

[PogoInTheWoods]

69412 is what I was guessing would work in the three finger cylinder. Still may with a different rod. Would like to see a 69030 for comparison. I thought the differences in pins were the lengths. Didn't realize there were different diameters, too. Now I know.

 

[Jethro 2t sniffer]

69412 is what I was guessing would work in the three finger cylinder. Still may with a different rod. Would like to see a 69030 for comparison. I thought the differences in pins were the lengths. Didn't realize there were different diameters, too. Now I know.

Well you got a shiny new ashtray now lucky it wasn't crazy expensive off ebay

 

[Maintenance supervisor]

69412 is what I was guessing would work in the three finger cylinder. Still may with a different rod. Would like to see a 69030 for comparison. I thought the differences in pins were the lengths. Didn't realize there were different diameters, too. Now I know.

So it doesn't fit the rod small end?

 

[Jethro 2t sniffer]

Wait does this mean it's got a crank or rod from a later saw or is there a full skirt piston with the right pin to fit?

 

[PogoInTheWoods]

Wow. Sorry. I neglected to post the piston pic. The pin/small rod end requirements are pretty obvious with them side by side. Longer rod and smaller diameter pin required for the new piston on the right..., or a different full skirt piston with the larger pin boss configuration for the rod currently on the crank.

​

 

[heimannm]

The CP80 DX was, I am told, a "designated export" model. My CP80 DX can from Japan, the CP60 DX came from California. The are both essentially SP models but should have an extra brace on the front wrap handle.







Mark

 

[Jethro 2t sniffer]

The CP80 DX was, I am told, a "designated export" model. My CP80 DX can from Japan, the CP60 DX came from California. The are both essentially SP models but should have an extra brace on the front wrap handle.

View attachment 802044

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Mark

Cool thanks Mark. Never seen that brace before

 

[Jethro 2t sniffer]

Wow. Sorry. I neglected to post the piston pic. The pin/small rod end requirements are pretty obvious with them side by side. Longer rod and smaller diameter pin required for the new piston on the right..., or a different full skirt piston with the larger pin boss configuration for the rod currently on the crank.

View attachment 801923​

That's very different. Was thinking aww yup ok smaller pin but a whole different height rod and all far out this bloody saw

 

[vinnywv]

The CP80 DX was, I am told, a "designated export" model. My CP80 DX can from Japan, the CP60 DX came from California. The are both essentially SP models but should have an extra brace on the front wrap handle.

View attachment 802044

View attachment 802043

View attachment 802045

Mark

Does that extra brace make any difference felt while running? I have a sp81 with a screw in the tank at that spot and i always wondered what it was for, now i know! Thats cool.

 

[PogoInTheWoods]

I think I have this rod/pin/piston compatibility thing sorted out now. And while it looks like I could simply change to the correct rod for the smaller pin piston, after revisiting the IPL's and having a better grip on what I'm looking at, I called Bob J. to see if he might have the piston listed in the early 7-10 IPL (that I just should have ordered in the first place had I not been overthinking this whole thing so much). He did, so I bit the bullet and ordered it..., a 69030 which should be the large pin version of a full skirt 2" piston with thick rings for a cast iron bore three finger transfer cylinder. Thing is, the piston that supersedes that number is the latest 85239 universal 2" replacement that supposedly is the miracle service upgrade for all the 70cc saws..., except for the ones with incompatible connecting rods, of course. Guess what they get? Yup. 85240 LOL

So anyway, I found a pretty clear break point in a 1972 6-10 IPL that lists both large and small versions of the piston/connecting rod assemblies for what was obviously a transitional period toward the more beefy pin boss design. It also references the same crank and cylinder assembly for both large and small connecting rods, (at least in this particular IPL), so that question seems to have been answered to some extent as well. A side note there would be the possibility of using the common 85352 10 series connecting rod on the older 70cc saws for using large pin pistons where they might be applicable (or desired?). Just a thought.

(A and B Codes denote the smaller pin configuration.)​

​

 

[PogoInTheWoods]

Got to digging a little more and came up with this pic Mark posted last summer of the 85239 piston( listed as being the replacement for the 69030) compared to an oversized version of the 69030 (69031) which seems to indicate the 69030 itself is indeed a windowed piston, albeit a thick ringed one.

I'm now officially getting dizzy from chasing my tail.

​

 

[Maintenance supervisor]

I think I have this rod/pin/piston compatibility thing sorted out now. And while it looks like I could simply change to the correct rod for the smaller pin piston, after revisiting the IPL's and having a better grip on what I'm looking at, I called Bob J. to see if he might have the piston listed in the early 7-10 IPL (that I just should have ordered in the first place had I not been overthinking this whole thing so much). He did, so I bit the bullet and ordered it..., a 69030 which should be the large pin version of a full skirt 2" piston with thick rings for a cast iron bore three finger transfer cylinder. Thing is, the piston that supersedes that number is the latest 85239 universal 2" replacement that supposedly is the miracle service upgrade for all the 70cc saws..., except for the ones with incompatible connecting rods, of course. Guess what they get? Yup. 85240 LOL

So anyway, I found a pretty clear break point in a 1972 6-10 IPL that lists both large and small versions of the piston/connecting rod assemblies for what was obviously a transitional period toward the more beefy pin boss design. It also references the same crank and cylinder assembly for both large and small connecting rods, (at least in this particular IPL), so that question seems to have been answered to some extent as well. A side note there would be the possibility of using the common 85352 10 series connecting rod on the older 70cc saws for using large pin pistons where they might be applicable (or desired?). Just a thought.

(A and B Codes denote the smaller pin configuration.)​

View attachment 802142​

Ok I understand the piston thing now , but the center of that piston pin with the full skirt looks closer to the top of the piston which would move it down farther from the combustion ring , unless the picture just makes them look the same height?
If the crank throw and rod stay the same but you move the hole for the connecting rod up or down it changes the compression. Chevy guys buy special stroker pistons with the hole moved up.

 

[Maintenance supervisor]

Got to digging a little more and came up with this pic Mark posted last summer of the 85239 piston( listed as being the replacement for the 69030) compared to an oversized version of the 69030 (69031) which seems to indicate the 69030 itself is indeed a windowed piston, albeit a thick ringed one.

I'm now officially getting dizzy from chasing my tail.

View attachment 802148​

Piston height would effect the port timing , right?

 

[PogoInTheWoods]

Skirt length and shape would. The windowed and full skirt pistons pictured earlier each use a different connecting rod.