Some of those came from e-Bay, some from various parts collections I've picked up. You don't see them on e-Bay all the time, and some times they are incorrectly identified as kart carburetor parts.
Mark
Mark
McCulloch Chain Saws
- Thread starter Bruce Hopf
- Start date
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Got another PM 700 question. After rebuilding the carb and trying it out at the Iowa GTG, it would run WOT ok but will not idle at all. No matter what adjustments I made it would not idle or for only a second or 2 then die. I was told it's leaking somewhere, any ideas? Thanks.
Where to you have the L adjust set? I generally start around 1 to 1-1/2 turn open.
Is the idle speed screw and mechanism properly adjusted to hold the throttle open just a bit? I don't remember specifically on the PM700 but many of those saws had an external idle adjust screw with a large tapered end that contact the arm on the throttle rod, sometimes I find it necessary to bend the arm a bit to achieve the proper contact with the idle adjust screw. If the idle speed screw is not holding the throttle open far enough the saw would die.
Could be an air leak, plug the intake and exhaust ports and try to pressure or vacuum test the crankcase to make sure it is holding. Look carefully at the PTO side seal, often they are damaged from grass, string, etc. that get wound up in the clutch or chain and eventually around the crankshaft at that point.
Check the compression as well, a lot of piston ported saws will start and run at higher speeds O.K. but can't be adjusted at idle due to low compression.
Mark
Is the idle speed screw and mechanism properly adjusted to hold the throttle open just a bit? I don't remember specifically on the PM700 but many of those saws had an external idle adjust screw with a large tapered end that contact the arm on the throttle rod, sometimes I find it necessary to bend the arm a bit to achieve the proper contact with the idle adjust screw. If the idle speed screw is not holding the throttle open far enough the saw would die.
Could be an air leak, plug the intake and exhaust ports and try to pressure or vacuum test the crankcase to make sure it is holding. Look carefully at the PTO side seal, often they are damaged from grass, string, etc. that get wound up in the clutch or chain and eventually around the crankshaft at that point.
Check the compression as well, a lot of piston ported saws will start and run at higher speeds O.K. but can't be adjusted at idle due to low compression.
Mark
Nickolas
Retired and messing around with old stuff...
You can try soaking the diaphragm in brake fluid. I have done many like this and have been able to use them again instead of having to buy another. I've been rebuilding carbs for over 30 years. One of my favorite things to do besides tearing motors apart. All I do these days is rebuild old saws and work on boat motors or anything else that moves. Try the brake fluid though it may get you back in action if it's not too far gone.
Nick
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I'll start with the carb adjustments you suggested, think I only had the L at 3/4 of a turn out. Haven't checked the idle speed screw either but I'll give it a look-see. Usually I leave that alone most of the time.
The saw appears to be a 1-86 geardrive. I cannot clearly make out the numbers on the crankcase pic, however it appears to have 1-76 stamped there as well as 1-86 underneath that? Another giveaway is the completely coated handle.
A nice saw - well done.
Chris
It may have been a 1-86 from the beginning, or may have started life as a 1-76 and the gearbox added later. I have a 1-76 and a 1-86, a couple of old work horses indeed. The 1-86 appears to have started out as a 1-76 and was converted to 1-86 and received a 0.030 over bore. Looks like a crude attempt to change the serial number as well.
The 1-86 after some TLC
I gave the 1-76 a good workout on some locust in 2011
Mark
The 1-86 after some TLC
I gave the 1-76 a good workout on some locust in 2011
Mark
The saw could use a muffler and a carb cover that is not missing pieces but other than that seems OK.
tpence2177
ArboristSite Operative
Got that Mac 110 running without a carb kit. Have one on the way just in case. Got that 12" bar and chain on the way as well and it will be good to go!
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I have a MM25 apart right now, seemed to have very low compression. I told him it would be at least $100 to make it right, he said go ahead...
McCulloch made quite a few variations in the MM series, chrome plated bore with an aluminum piston, aluminum bore with a chrome plated piston, and open as well as closed port designs.
This particular one is (was) closed port, aluminum bore, and chrome plated piston. Not much chrome left on the piston and the bore is pretty scratched up.
It doesn't take many tools to disassemble a MM.
It took me about 40 minutes from start to this point.
I have a few cylinder/crankcase kits and pistons in the attic, carb kits, seals, etc. on hand so just some time to clean it up and put it back together.
Mark
McCulloch made quite a few variations in the MM series, chrome plated bore with an aluminum piston, aluminum bore with a chrome plated piston, and open as well as closed port designs.
This particular one is (was) closed port, aluminum bore, and chrome plated piston. Not much chrome left on the piston and the bore is pretty scratched up.
It doesn't take many tools to disassemble a MM.
It took me about 40 minutes from start to this point.
I have a few cylinder/crankcase kits and pistons in the attic, carb kits, seals, etc. on hand so just some time to clean it up and put it back together.
Mark
tpence2177
ArboristSite Operative
I may need to rebuild the carb after all. It didn't seem to like to crank after it got warm yesterday cleaning up a downed tree. I have a kit here waiting, just thinking about running it some more and trying to dial in the tuning to see. No scoring or anything but the piston is a little brown lower down? Is that a bad sign?
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Not a bad sign. It's pretty common. I figured it was when people used to run higher ratio oil gas / mix. I think I'v seen pics of it on newer saws as well. Maybe from running too rich?
tpence2177
ArboristSite Operative
Ok thank you I have been running it rich just in case I run 40:1 opti 1synthetic oil with non ethanol gas. May just need to lean it out some didn't know how well the carb was working so I would rather it run rich than lean lol.
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ML12
ArboristSite Guru
Managed to get out over the long weekend and find some large wood to test the 795 in. Also milled up some nice 3" x 20" x 6' maple slabs, and some small red cedar.
tpence2177
ArboristSite Operative
So went to crank my mac 110 today and the crankcase was full of bar and chain oil. I thought I read a fix for it a few pages back, but I can't find it anymore. Any thoughts? Isn't there an o ring for the oiler or something like that, that I should replace?
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Item 12 is the o-ring in question, you can get by just taking the front cover off the saw to get at it. I don't know the standard size off the top of my head but you won't have any trouble finding a replacement. Easiest way is to measure it up, check out McMaster Carr for the standard size, buy a pack of 100, then send 5 or 10 to each of your Mini Mac enthusiast buddies.
Mark
tpence2177
ArboristSite Operative
Awesome thank you very much sir! I got the tank pulled off this morning and the tubing that connects from the pump to the bar chain oil tank has a weird bend in it. Is there a reason it presses up against the tank but has no opening? Was thinking about running a new line but wasnt sure about that bend.
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tpence2177
ArboristSite Operative
I don't see the oiler at all in my saw... I took some pictures just now to make sure I'm not missing anything? I know it's super dirty going to clean it up before I put it all back together.
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That saw appears to be the manual oiler only version without the automatic pump; your "110" must be a victim of a Frankensaw since all of the 110's would have been equipped with an automatic oil pump. Look carefully in the bottom of the automatic oiler base, there should be a hole into the crankcase (circled in red) for the impulse to operate the automatic oiler; if your saw run without the automatic oil pump in place there is no passage open between the base and inside of the crankcase. If that saw doesn't have the impulse passage open to the crankcase, the crankcase bottom or maybe the whole cylinder and crankcase have been replaced. I don't know any path for bar oil to get into the crankcase in the manual only oiler versions.
Mark
Mark
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