McCulloch Chain Saws

[vinnywv]

I started a cp125 one time and forgot to put that compression release lever back off...lol. it took a couple moments of me scratching my head as to why it sounded so weird. It would even rev up ok. Just hard to tune. Once i figured that out it really sounded loud and started dancing on the floor.sometimes the excitement blinds me.

 

[PogoInTheWoods]

Any loose fitting in the cylinder is BAD even for a short run time.

I tend to agree and probably shouldn't have made the suggestion..., especially since I'll be fixing this later this morning! 'Course this didn't happen just by starting the saw with a loose plug to see if it would run. Takes quite awhile for one to get this bad. (Threads are basically gone.)

​

 

[Marvin Booysen]

Hi guys, I finally got around to my 7-10/PM700 frankensaw yesterday. It's got three ignition mounting holes on the cylinder (like the second cylinder in Mark's post #39,565), and there appear to be no points provisions behind the flywheel, so seems to be a 700 powerhead indeed. The fuel tank leaked like a sieve, it's now better after sitting overnight, but still leaks into the carb compartment.



Unfortunately, I'm having no luck gettting it started, not a pop. To me, the compression doesn't feel great (I don't have a gauge), though I remember thinking the same of my 10-10A when I got it, and now it feels good and runs very well. I dripped some fuel down the carb throat, but nothing. The previous owner said he apparently rebuilt the carb recently; I set the H & L needles to 1 1/4 turns out (they were close as I recall), with the idle just touching, but also turned the latter in a bit more later. The saw doesn't have a throttle lock like my 10-10A, I also tried holding the trottle open a bit while pulling, to no avail.

I checked the spark plug a couple times, it has spark every time (ground to cylinder, the spark seems nice and bright blue colour). It needs a spark plug boot, and I thought (hoped) maybe it's getting robbed somewhere, but I don't see any obvious breaks in the cable insulation.
So now I don't know, guess I'll pull the carb and muffler to check the piston/cylinder? I've only ever done basic maintenance on my 10-10A, never even rebuilt the carb, so any advice, perhaps stuff to try before starting to tear it down, would be very much appreciated!

 

[vinnywv]

Does it have good compression with the button out? It should hold itself by the rope for sure.

Rebuilding a carb for a beginner...my advice is to take pictures for yourself of each step. Each side of gasket and diaphragm so it goes back together right. Have the rebuild kit on hand and lay each part per side together so you dont get confused. Ive found that a product called goof off will eat old varnish away very very well. I also use a sharp pocket knife or a flat razor blade to get the old gaskets off the carb body. As anything take your time and look at each thing to see where they go. If you get stuck ask away. We all were in your shoes at one point. Theres a lot of guys who are very willing to help.

 

[Marvin Booysen]

Thanks Vinny, that’s a negative on the staying up by the cord though, even with button in out position. The saw flops all the way down, but slower than with button in

 

[edju1958]

That's not a good sign.I'd have to say the compression is too low for your saw to fire.You might want to get yourself a compression tester.You can pick them up fairly cheap at Auto Zone for around $20.That was one of my first "specialty" tools I bought when I started working on saws.
There's another possibility that the rings could be stuck if the saw hasn't been run a long time.Try filling the cylinder with a good penetrating lubricant,work the piston up & down a couple times,refill with more lubricant & let it set for a couple days.If your compression doesn't come up more than 5-10 lbs.,then I'd say your rings need replacing.

 

[edju1958]

Back to my 5-10 woes.I went to put the points back in & set the gap yesterday & that's when it started going downhill.I always put the nut on the crank to turn the engine over with a socket to see when the points break.I could only get the flywheel to turn 1/4 turn after I put the flywheel back on.It dawned on me that one of those stinking little washers had fallen off one of the needle extensions & it must've fallen into the open throat of the carb & went down into the cylinder.Now it looks like I'll have to pull the saw apart to get that little stinking washer out of the engine if I can.I guess it'd be an opportune time to put new rings in the saw.

 

[Marvin Booysen]

Thanks edju, I'm going to try it!
So I'd work the piston up to above the transfers, spray lots of WD40 through the sparkplug hole, let it sit a bit and work it up and down. Then move it above the transfers again and spray more and let it sit closed for a few days?

 

[PogoInTheWoods]

Pull the muffler and inspect your piston before wasting time on anything else. If it's scored, you'll find your problem and a course of action can be established. If it's clean, more diagnosis is obviously in order. But you've at least accomplished something instead of spraying WD-40 at the problem with a hope and a prayer that it miraculously fixes it. My guess is it'll just make a mess.

 

[Marvin Booysen]

Ok, thanks Poge. So I'd first inspect the piston through the exhaust port (would I be able to establish if the rings are stuck too?), then if it looks good, try other options like the lubricant.
I'd have to remove the cylinder shroud to get at the muffler right? I have a Mac workshop manual, and I think I remember them saying that once the airbox and handle brace bolts are removed, the shroud can be slid off to the side somehow, or will I have to remove the whole tank/handle/carb?

 

[PogoInTheWoods]

There is access to the bottom muffler bolts through the shroud, but I would still remove it to get a better visual on what you have. Here's an IPL if you don't have one already. It covers most iterations of the 7-10. Removing the shroud is simple and pretty much as you described it. Remove a few fasteners and that should be it.

 

[Maintenance supervisor]

Ok, thanks Poge. So I'd first inspect the piston through the exhaust port (would I be able to establish if the rings are stuck too?), then if it looks good, try other options like the lubricant.
I'd have to remove the cylinder shroud to get at the muffler right? I have a Mac workshop manual, and I think I remember them saying that once the airbox and handle brace bolts are removed, the shroud can be slid off to the side somehow, or will I have to remove the whole tank/handle/carb?

I've snuck the shroud off without removing the whole tank. Just fyi theres a tiny allen head bolt in the oil tank going into the fuel tank, dont break your fuel tank.
Like Poge stated put eyes on your piston and cylinder, I would also pull the carburetor off and look at your intake side (flashlight helps) and when you pull the muffler be mindful that carbon deposits will fall into the cylinder if your not careful.
Most McCullochs can tolerate a pretty terrible piston and run , I've got a lefty 10-10 that needs rebuilt and the piston looks like a pitbull has been chewing on it, but it will run stuck rings and all.

 

[Marvin Booysen]

Thanks for all the advice guys!
@Maintenance supervisor: thanks for the heads-up with that bolt from the oil tank; so I'd remove the oil tank lid, and then it's there in the top going through to the fuel tank. I think I see it in Poge's IPL, part 56 in Fig 1 Also, did you just wiggle the shroud out between the cylinder and tank/handle? I saw that the shroud is kind of "raised"/irregular around the hole for that bolt that goes throught the back the carb compartment (has a lockplate), through the shroud and into the cylinder. I'm thinking of trying this first, just to get a peek at the piston, but probably also good to get the tank off for a good cleaning.

 

[Maintenance supervisor]

Thanks for all the advice guys!
@Maintenance supervisor: thanks for the heads-up with that bolt from the oil tank; so I'd remove the oil tank lid, and then it's there in the top going through to the fuel tank. I think I see it in Poge's IPL, part 56 in Fig 1 Also, did you just wiggle the shroud out between the cylinder and tank/handle? I saw that the shroud is kind of "raised"/irregular around the hole for that bolt that goes throught the back the carb compartment (has a lockplate), through the shroud and into the cylinder. I'm thinking of trying this first, just to get a peek at the piston, but probably also good to get the tank off for a good cleaning.

Well you gotta pull pretty hard to get it out after removing the bolt in the air box , I also loosen the carburetor bolts, it went back in alot easier.
And yes remove the oil tank cover to access the bolt.

 

[vinnywv]

So i was asked several weeks ago if not longer if id be willing to work on a sp81 chainsaw. Of course i said yes. I was asked by a pal from new zealand for a gentleman who lives in new york state. The saw was shipped to my house from iowa. It arrived as most do a very dirty saw. But it was complete. I got the chance to start on it and took it apart. There was a large score on the piston i could see so the engine was torn down. Turned out it was just the piston. Shweeeew. So the cylinder is in good shape. Very lucky there. So i gathered a list of parts and called the ol mac guy bob j. He sent me a new piston for the B cylinder(lucky there too). A new bottom brace cause this one was missing a lot of it, new seals, exhaust gasket, and a couple other little things. Waiting on parts, its time to clean this mess up. Likely took 1/2 pound of oily sawdust out of it and gave it a good scrubbing. Every ounce of it!! Cleaned and waiting parts. It had a spur sprocket on it, cant have that. So a new old rim drum i had went on it. Got a few new allen screws for the engine block, a few other fasteners from my hoard and waited......fast forward to a week ago and the parts showed up. I was excited for this cause it was in really good shape. I had to work all week but was off friday. I got home thursday evening and got started. Took my time but 2.5 hrs later i had a complete engine sitting on the bench. Including flywheel and points, av mounts, and rear shroud. Carb boot as well. The next morning (friday) i got busy again. My goal was a running saw by lunch. My goal was met. After a few more hours i had a complete, clean, sp81 to look at and put fuel in. The owner sent me a nos sdc37 carb for it. Original was the 51a(fixed jet). They are good but the 37 is a snappy carb. Outside i go to add fuel. Put in some 32:1 fuel....no leaks!! Great so lets set it on the ground and see how we did i thought. 8 pulls later its running!!!!! And idling on its own but wont rev up??? Someone forgot t attach the linkage to the trigger!! Guilty. After a short fix i tried it again and boy oh boy we have a runner!!!! I mean a good runner. I was happy with that. Fast forward the owner says to try it out....but its soooo clean. So today i try it out. What a great runner and with a 20" bar a very strong cutter. So now a guy whos been wanting one for awhile im told now has a great classic strong running mcculloch muscle saw. I was very glad to be asked and trusted. Ive yet to even speak to the owner. Just emails and texting. So, Edju1958....thankyou for the opportunity. And mr. Boorer of course. Heres some pictures. I hope you enjoy your new saw!!!

 

[Jethro 2t sniffer]

So i was asked several weeks ago if not longer if id be willing to work on a sp81 chainsaw. Of course i said yes. I was asked by a pal from new zealand for a gentleman who lives in new york state. The saw was shipped to my house from iowa. It arrived as most do a very dirty saw. But it was complete. I got the chance to start on it and took it apart. There was a large score on the piston i could see so the engine was torn down. Turned out it was just the piston. Shweeeew. So the cylinder is in good shape. Very lucky there. So i gathered a list of parts and called the ol mac guy bob j. He sent me a new piston for the B cylinder(lucky there too). A new bottom brace cause this one was missing a lot of it, new seals, exhaust gasket, and a couple other little things. Waiting on parts, its time to clean this mess up. Likely took 1/2 pound of oily sawdust out of it and gave it a good scrubbing. Every ounce of it!! Cleaned and waiting parts. It had a spur sprocket on it, cant have that. So a new old rim drum i had went on it. Got a few new allen screws for the engine block, a few other fasteners from my hoard and waited......fast forward to a week ago and the parts showed up. I was excited for this cause it was in really good shape. I had to work all week but was off friday. I got home thursday evening and got started. Took my time but 2.5 hrs later i had a complete engine sitting on the bench. Including flywheel and points, av mounts, and rear shroud. Carb boot as well. The next morning (friday) i got busy again. My goal was a running saw by lunch. My goal was met. After a few more hours i had a complete, clean, sp81 to look at and put fuel in. The owner sent me a nos sdc37 carb for it. Original was the 51a(fixed jet). They are good but the 37 is a snappy carb. Outside i go to add fuel. Put in some 32:1 fuel....no leaks!! Great so lets set it on the ground and see how we did i thought. 8 pulls later its running!!!!! And idling on its own but wont rev up??? Someone forgot t attach the linkage to the trigger!! Guilty. After a short fix i tried it again and boy oh boy we have a runner!!!! I mean a good runner. I was happy with that. Fast forward the owner says to try it out....but its soooo clean. So today i try it out. What a great runner and with a 20" bar a very strong cutter. So now a guy whos been wanting one for awhile im told now has a great classic strong running mcculloch muscle saw. I was very glad to be asked and trusted. Ive yet to even speak to the owner. Just emails and texting. So, Edju1958....thankyou for the opportunity. And mr. Boorer of course. Heres some pictures. I hope you enjoy your new saw!!! View attachment 882907View attachment 882914View attachment 882916View attachment 882917View attachment 882918

Great job vinny

 

[Jethro 2t sniffer]

I did a little project.

Was jealous of you guys and fairlead type starters

So.....


Was a fiddly we job but I'm stoked as

 

[heimannm]

This is an earlier version of the 10 Series anti-vibe saws (CP70), notice the three piece starter screen. These were also found on some early 7-10 saws.



Mark

 

[Brushswamper523]

Alright. The PM 850 is finished. I had some gas leak out of the fuel tank and mess my new paint up on the tank. (I plan to fix the paint once I fix the lid or find a replacement). Started it up and pulled it through some wood today. It chewed through the softwood awesome.. I need a better chain it came with one of those 3/8 low kickback chains (awesome not). But here it is. Be gentle first one.

 

[2broke2ride]

Hello saw friends, I haven't had much time to work on Macs lately, been overun with snowblowers, finally got caught up last weekend so I got some saw time today. I got a customers SP70 back together and running good today and also got some time to work on my scrap heap SP81. It is going together well, just need to clean up the fuel tank and rebuild the carb. This one has a LRB piston in it, hopefully it is a good runner.

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