MCCULLOCH The official McCulloch thread

[Steve]

Very interesting. Do you possibly have a PN reference? I plan on using the head, so I am trying to figure out my best option. I do worry about losing compression unless I plug the hole all the way to the inner wall or else find the appropriate valve and throw it in. Any ideas?

Thanks for the quick replies.

Give me a few hours to get home. I have what you need/want.

 

[Mac131]

Looks like a 54cc saw. Piston measurement is slightly under 1 3/4". Also has a one piece bearing and seal on the flywheel side.... interesting.

 

[Mac131]

Give me a few hours to get home. I have what you need/want.

Awesome, thanks!

 

[Steve]

Looks like a 54cc saw. Piston measurement is slightly under 1 3/4". Also has a one piece bearing and seal on the flywheel side.... interesting.

That is the best bearing/seal combination in my opinion because the seal is still available. National 471551 is the number.

 

[heimannm]

It is not a one piece bearing and seal, the bearing has a wider outer race and the seal is pressed into it.

You will need to identify the model and serial number of the saw in order to correctly identify the part number for the DSP piston, then you will need to find the other components like the bracket, spring, and lever that operate the valve. There were several different part numbers for the DSP pistons and the dimensions are all different.

Another option would be to turn a screw down to the correct length and diameter to plug the hole, tap the boss to accept the threads, and just plug it.

This is a 7-10 with the same type of DSP (De Stroking Port) or compression release. If your saw is 1.75" bore with this kind of compression release is may be a 3-10 DSP, or perhaps the cylinder came from one of the electric start saws that had the same DSP arrangement.



I expect to tear down another 7-10 this week with the same DSP arrangement, I will try put up some photos for a better explanation.

Mark

 

[heimannm]

Steve - the larger O.D. seals are also available, the McCulloch part number is 67095 and is the same (bearing and) seal as used on the 600 Series saws. I don't remember the dimensions off the top of my head but I think it is .562" shaft and 1.5" bore.

Mark

 

[Steve]

Steve - the larger O.D. seals are also available, the McCulloch part number is 67095 and is the same (bearing and) seal as used on the 600 Series saws. I don't remember the dimensions off the top of my head but I think it is .562" shaft and 1.5" bore.

Mark

Didn't know that. Is it an aftermarket seal or a NOS deal?

 

[Mac131]

It is not a one piece bearing and seal, the bearing has a wider outer race and the seal is pressed into it.

You will need to identify the model and serial number of the saw in order to correctly identify the part number for the DSP piston, then you will need to find the other components like the bracket, spring, and lever that operate the valve. There were several different part numbers for the DSP pistons and the dimensions are all different.

Another option would be to turn a screw down to the correct length and diameter to plug the hole, tap the boss to accept the threads, and just plug it.

This is a 7-10 with the same type of DSP (De Stroking Port) or compression release. If your saw is 1.75" bore with this kind of compression release is may be a 3-10 DSP, or perhaps the cylinder came from one of the electric start saws that had the same DSP arrangement.

View attachment 286545

I expect to tear down another 7-10 this week with the same DSP arrangement, I will try put up some photos for a better explanation.

Mark

Unfortunately I received that engine all by itself. Not sure I can trace it back. Thank you for all the info you provided. I will probably just tap it and plug it shut. I wonder if it is in fact a 3-10. The piston and cylinder are in great shape, so I may port it and build a 10-10 around it to see how she runs. Always nice to have a spare motor as well.

I have found the bearings and seals for the 10-10s. Good to know this design is around too. I wonder why Mcculloch abandoned this design? Also interesting the clutch side is keyed too. Again, I appreciate all the info.

Jeff

 

[Mac131]

Steve - the larger O.D. seals are also available, the McCulloch part number is 67095 and is the same (bearing and) seal as used on the 600 Series saws. I don't remember the dimensions off the top of my head but I think it is .562" shaft and 1.5" bore.

Mark

Do you mean 67905 for the bearing ?

 

[Mac131]

Didn't know that. Is it an aftermarket seal or a NOS deal?

67906 is a Mac P/N. I have ordered a couple recently. Also ordered the bearing, 67905.

 

[Al Smith]

I tried to cross reference the Mac seal number to CR but had no luck with it or National seal .

 

[Al Smith]

Here's what I found on two 10 series crank shafts . One the seal was internal to the bearing another was the same exterior size as the outer race of the bearing . The internal seal I could read the numbers which are McCulloch 61618 or CR number 5480 You can find them on flea bay .The larger seal I could not see any numbers except JAPAN inside the seal .Both crankshafts have a cam ground into them for a points system assumed to be a 10-10 or 6-10 righty or a lefty start 10-10 .That said remember it's a McCulloch and other numbers might work .
I didn't get out the micrometers to measure them and my verniers are metric .That plus I don't trust verniers .I'll do some more research

 

[Mac131]

Here's what I found on two 10 series crank shafts . One the seal was internal to the bearing another was the same exterior size as the outer race of the bearing . The internal seal I could read the numbers which are McCulloch 61618 or CR number 5480 You can find them on flea bay .The larger seal I could not see any numbers except JAPAN inside the seal .Both crankshafts have a cam ground into them for a points system assumed to be a 10-10 or 6-10 righty or a lefty start 10-10 .That said remember it's a McCulloch and other numbers might work .
I didn't get out the micrometers to measure them and my verniers are metric .That plus I don't trust verniers .I'll do some more research

Very interesting. I wonder if you can get the bearing (inner seal one) on eBay as well. So far I have found the bearing and seal (that are the same OD) and just the seal of the other one. Good information to know!

 

[Mac131]

Ported my first saw today....power mac 6. Just worked the lower transfers and polished the exhaust.

Stock one on top

 

[heimannm]

The other bearing with the wide outer race is hard to find. On the plus side, the flywheel side bearing is usually O.K. unless the saw was allowed to get wet.

Mark

 

[Definitive Dave]

This is my favorite thread on OPE right now, always good readin' and learnin'.
At this point I have a runner 795, two more large frame macs that aren't in my possession yet, a pair of CP125 cylinders, a pair of SP125 cylinders, a handful of crazy modified kart pistons, a NOS intake for dual reed cages, and a NOS 101B motor and carb. Previously sold every Mac I ever owned with disdain (they weren't Stihls LOL).
You guys have been super helpful in my research into these big ol' classics.
I replacement race model light piston for the SP125 is likely the first project that will head to Wiseco for production, but I am not there yet, still lots of reading and research to go.
Dave

 

[jacob j.]

This is my favorite thread on OPE right now, always good readin' and learnin'.
At this point I have a runner 795, two more large frame macs that aren't in my possession yet, a pair of CP125 cylinders, a pair of SP125 cylinders, a handful of crazy modified kart pistons, a NOS intake for dual reed cages, and a NOS 101B motor and carb. Previously sold every Mac I ever owned with disdain (they weren't Stihls LOL).
You guys have been super helpful in my research into these big ol' classics.
I replacement race model light piston for the SP125 is likely the first project that will head to Wiseco for production, but I am not there yet, still lots of reading and research to go.
Dave

I'll be finishing your box this weekend Dave with a bunch of Mac stuff and some other modern saw cylinders for bore + re-plate. Let me know if there's something you specific you're after.

 

[heimannm]

This is a 7-10 but the principle of the De Stroking Port or DSP is the same.

With the muffler off you can see the working parts as well as the port from the DSP valve to the muffler where the compression is redirected when the valve is open.



With the tank off you can see the top of the valve.



And the valve removed.



You will need to make some careful measurements down the bore of the DSP valve in order to come up with a suitable plug. If I make it to the other shop today and remember, I will try to get some photos of a plus someone else made for a similar saw.

Mark

 

[PogoInTheWoods]

There were several along the way. Interesting that there is no reference in the chart to this style DSP for early 7-10's. Perhaps just another indicator that early 7-10's were simply LH start 6-10A's. 84221 is indeed listed in the 1970 7-10 IPL.

​

 

[Mac131]

This is my favorite thread on OPE right now, always good readin' and learnin'.
At this point I have a runner 795, two more large frame macs that aren't in my possession yet, a pair of CP125 cylinders, a pair of SP125 cylinders, a handful of crazy modified kart pistons, a NOS intake for dual reed cages, and a NOS 101B motor and carb. Previously sold every Mac I ever owned with disdain (they weren't Stihls LOL).
You guys have been super helpful in my research into these big ol' classics.
I replacement race model light piston for the SP125 is likely the first project that will head to Wiseco for production, but I am not there yet, still lots of reading and research to go.
Dave

I would love to have a SP125! that's awesome you are collecting all these parts. Post pictures when you get started on it. It would be fun to see.