McCulloch Pro Mac 700

[half_full]

and without earplugs, you will be happy once it stops running. After listening to those saws in the early 80s it is a wonder we can hear at all.
Huh? What was that?

First time I ran my PM700 I had no ear protection with me. I actually purchased the saw from CL on my way to help a friend cut.
After a few minutes I had to switch to one of the other saws I had with me.

 

[rheima]

Unfortunately, I haven't been able to spend any time on the PM700. I had three saws apart on my workbench and thought maybe I should get them put back together before the parts start getting mixed up. I decided to start with the easiest (new ring and carb) and work toward the PM700 since it's in about as many pieces as it can possibly be. I finished one and got it dialed in, then I got tripped up by my "Girl saw" (electronic ignition conversion) project. I just finished it last night and now I can start on the Mac. Only problem is I'm having carpal tunnel surgery today, so it'll be at least another two weeks before I get started putting the yellow saw back together.

Ray,
I'll probably be branded a sissy, but I like the way that 031 sounds. I don't understand what Mark means by "that sound like a chain saw should", it sounded like a chain saw to me.

That makes two of us--------------------------------------I like the sound of my 031 and it makes me a very proud owner!!

Ray

 

[rheima]

Shouldn't run any saws without earplugs or muffs. Old loggers are always hard of hearing, no matter what saws they ran. Even those saws that sound like a vacuum cleaner or oven timer will do hearing damage. My old Macs, Homelites, and Poulans sound great with ear protection.

When I cut with my buds who all run modern saws, everybody turns and looks when I fire up one of my old workhorses. Without fail, one of my friends (including the fellow that I've quoted in my sig line) always tells me how good my saws sound afterwards. Makes me smile.:cool2:

Yes, once you shut them off!!


Ray

 

[2Twannabe]

Well, the doc said I'm supposed to take it easy for a few days and not lift anything over 5 pounds for two weeks. The problem is I'm not very good at taking it easy. So after I got a couple wheel barrows full of firewood up to the house, I decided to dig in to the PM700.

A loooong time ago, I put some pics on here of the p/c showing it had been seized pretty good. (I know... I'm an oxymoron). I always like to try to determine the cause of the failure. In this case, I think I've discovered two possibilities. The first is, it appears the saw was run for some time without a muffler gasket in place. The cylinder and cover are both scorched from hot exhaust gas. Is it possible? probable? that debris was drawn into the combustion chamber through this gap? The other is, it appears the crankshaft seal was either installed improperly or damaged using the old "pry under the flywheel with a screwdriver and tap the crankshaft with a hammer" method of flywheel removal.

Obviously, I'll replace both crank seals while I have it apart and put it back together with a new exhaust gasket, but do you think the exhaust could have contributed to this seizure?

Regards,
Jeff

 

[Eccentric]

My money's on a leaking crank seal being the culprit. Muffler gasket wouldn't do that.

 

[heimannm]

If it was carboned up badly in the muffler, then the muffler started to work loose it would certainly have broken loose bit of carbon, some of which got into the cylinder and scratched it up.

Mark

 

[2Twannabe]

The cylinder was certainly scratched up. Way more so than any lean seizure I've ever seen. I also have a very deep groove in the piston right about the location of the compression release hole. Are they prone to stick open on these saws?

Jeff

 

[2Twannabe]

I started putting the PM700 back together yesterday. I ended up using the used piston that came with the cylinder I bought off ebay instead of the NOS piston I bought. The NOS piston didn't come with a pin and the used pin I had was a really snug fit in the bearings. They didn't seem to want to turn at all with the pin installed. When I measured everything up, the used piston was actually a little better fit too. I don't have a manual for this saw, but I assume that .006 clearance between piston and cylinder is acceptable (measured about 5mm from the bottom of the skirt).

I used the new rings that came with the NOS piston, but this is the part that really concerns me - I had .060 ring end gap. I'll admit, I've not worked on old saws much, but that seems like too much ring end gap.

I'm not sure what the manual recommends for a sealer between the cylinder and crankcase, but I had Yamabond so that's what I used. I had to over torque the fasteners to get the gap to close up and squeeze out a little sealer and even then I'm not convinced I won't have a leak. I definitely want to do a leak down test before I go much further. I stopped there.

Feel free to comment and don't be shy about telling me if I really screwed something up.

Thanks for the help.

Jeff

 

[heimannm]

If you measured the end gap by pushing the ring into the bore, you are missing the fact that there is locating pin on the piston that will fill up a good portion of that gap. I have not really come up with a precise way to check the ring end gap on saws with locating pins.

0.006" is clearance between the piston skirt and cylinder is not too bad, depending on which set of numbers you believe in the original piston and cylinder chart, the min/max difference on the 7-10 was 0.0055" (top of piston to largest bore). The smallest bore to largest skirt dimensions listed work out to 0.0017" clearance which would be a little snug for my tastes.

Be sure to pressure and vacuum test the crankcase before you to too far along. I had one leaker last year that was fixed by a second attempt with a repeat coat of 1194.

Mark

 

[2Twannabe]

I've long since got over being a perfectionist, but I really didn't like the way the cylinder and crankcase went together last night. I took them apart and cleaned all the sealer off both sides and them put them back together without the crankshaft. When I held it up to the light, I could see a sliver of light on both sides of the clutch side bearing journal. When I put the bearing in the clutch side and torqued down the big screws inside the bar oil resevoir, it got disturbing...

I measured the gap on this side at .006. Probably could live with that.

This side measured .011.

Is gasket sealer going to be enough to take care of this or should I be thinking about some machine work?

Jeff

 

[half_full]

Just a thought. Is there supposed to be a gasket there?

 

[2Twannabe]

Just a thought. Is there supposed to be a gasket there?

No, it just fits together with gasket sealer. Or at least it's supposed to. Just for curiosity sake, I fitted up the original cylinder an torqued to specs and there is no gap at all. The cylinder and crankcase are machined as a set, or at least I think I read that somewhere. I was concerned about this when I decided to replace the cylinder, and I guess rightfully so.

 

[heimannm]

It appears you have no screws holding it together???

What happen if you use all 8 screws (4 x 12-24 and 4 x 8-32) and tighten everything up?

I have at least one (PM55) where I swapped cylinders, kept the original crank case bottom and everything bolted up and sealed up just as it should. I am guessing with all of the screws installed and tightened the gaps will dissappear.

Mark

 

[2Twannabe]

In the pictures, I have the four big screws inside the oil tank torqued to the high end of the range specified. The smaller screws didn't make enough difference to even notice when I put them in.

I'm going to measure the used piston I bought against the original cylinder. If it's not too sloppy, I'm going to put it together that way and see what I get. I'm just looking for a runner. As you said before, it doesn't have to be perfect.

Jeff

 

[Gearhead1]

The cylinder and crankcase were indeed machined as a matched set. McCulloch factory advice was never to mix and match. That being said, I know of several guys who have swapped used parts and had success.

 

[2Twannabe]

If the saw I have is the pinnacle of McCulloch engineering, then I can certainly understand why they're not still in business. They obviously didn't have a grasp of the concept of mass production or serviceability. My 031AV may be a girl saw, but I'll bet I can take the cylinder off it and it'll fit on any other 013AV ever made. Sorry, but I'm just not sold on the whole McCulloch thing at this point. Somebody make me a believer, or pm me an offer.

Hoping, but not optimistic,

Jeff

 

[jughead500]

Comparing the 031 to the Clamshell Mccullochs is like comparing apples to Oranges.Not to Argue or anything but some Motorcycle manufactures in the early 70's machined the Bottom cases (Suzuki and Kawasaki on the Twin and triple two Strokes) as matching sets.The 031 had a Flat Surface mating to a Flat Surface without the Crankshaft being in the Equation.
A better comparison would be the Stihl Clamshells to the Mccullochs.They have about the same fit as the Mccullochs as I have found when mismatching cylinder bottoms to new (OEM) cylinder kits.One Being to mismatching an 025 top and Bottom and Second a MS390 Bottom to a New MS310 top.BUT with a Little Lapping on Glass with sandpaper and final lapping with compound on the bottoms they fit Quite Snuggly.

Did you take your Cylinder top and bottom apart in a sequence?Looks to be warpage.

 

[heimannm]

If the saw I have is the pinnacle of McCulloch engineering, then I can certainly understand why they're not still in business. They obviously didn't have a grasp of the concept of mass production or serviceability. My 031AV may be a girl saw, but I'll bet I can take the cylinder off it and it'll fit on any other 013AV ever made. Sorry, but I'm just not sold on the whole McCulloch thing at this point. Somebody make me a believer, or pm me an offer.

Hoping, but not optimistic,

Jeff

NO SOUP FOR YOU!!

If you're ready to give up on it shoot me a price, I am making a trip back and forth across IL next week and may be able to take the problem child off your hands...

Mark

 

[roberte]

If the saw I have is the pinnacle of McCulloch engineering, then I can certainly understand why they're not still in business. They obviously didn't have a grasp of the concept of mass production or serviceability. My 031AV may be a girl saw, but I'll bet I can take the cylinder off it and it'll fit on any other 013AV ever made. Sorry, but I'm just not sold on the whole McCulloch thing at this point. Somebody make me a believer, or pm me an offer.

Hoping, but not optimistic,

Jeff

Too bad its not working out for you. The 700s are good saws.
All things being equal, If I had to choose right now, Mac 700 vs Insert equal model brand here,
Mac 700.

 

[2Twannabe]

NO SOUP FOR YOU!!

If you're ready to give up on it shoot me a price, I am making a trip back and forth across IL next week and may be able to take the problem child off your hands...

Mark
Mark

I know! I know! And I was hungry too.

I owe all of you guys that have been so generous helping me with this saw a huge apology. I spoke out of frustration more than anything. This saw has been sitting on my workbench in pieces since the middle of December waiting to get a decent used cylinder for a reasonable price so I can put it back together. I finally found a decent deal on a cylinder and... well if you've been following this thread you already know.

Last night I started putting the saw back together and everything I touched turned to crap. I made more work for myself than I did progress. I finally had to walk away from it before I did something really stupid.

I'm not ready to give up just yet, but I do apologize for talking bad about your beloved yellow brand.



Mark,

I tried to PM you, but your inbox is full. Where do you want me to send all the parts I'm not going to use?