McCulloch Chain Saws

[rwoods]

Well all this chain brake business got me in the mood to look at my two PM800s that keep firing prematurely. One has a sloppy fit due to the pivot pin backing out. I was unable to tighten it enough to work, but fossil's photo got me thinking about how to improve these models where the stem of the spring lever rides on the trigger rather than the lever's nipple as it always seemed strange to me that the trigger would be shaped for the nipple but actually bore down on the stem. I thought about modifying the trigger either by grinding a vertical groove to accept the stem or welding a tab on the trigger. Since I can't weld and time was short, I remedied the problem by putting two washers behind the trigger so now the stem is behind the trigger and the nipple rides on the trigger. Results in a slight misalignment of the band but does not interfere with its function. I am concerned however that with lessening of the inserted length of the pivot pin shank it may fall out after the brake is activated. May need to readdress it. See pictures below.



Locked and loaded.



Fired position.


Better view showing stem behind the trigger.


I determined that the other chain brake's issue was the opposite end of the trigger. The spring stays in place but the trigger does not hold the handle very securely. Just takes a little touch and it fires. a project for another day.

Ron

 

[rwoods]

Sorry about the upside down pictures. Ron

 

[rwoods]

I'll have to look a the others to see if I have anything different. Regardless, pretty good brake systems compared to the early stuff the other manufacturers had

What model saw was that? The spring and trigger might work as a replacement for me. Any ideas of the part numbers? Ron

 

[fossil]

Not sure Ron. It came to me on an SP80 so I don't think it's original to the saw.

Have a look at the brake diagram on this SP81 IPL It seems to be similar. If you need me to pull it apart or verify anything, let me know.

 

[rwoods]

Thanks. I just happen to have one of those in inventory. The trigger is thinner with a welded pivot pin that rotates in the housing. It was much harder to set off than my others - could be the design or the fact it is unused. Nonetheless I'm not sure what MAC was thinking with the change to the wider trigger shaped for the new style spring but without actually fitting the new spring. Ron

 

[Nickolas]

McCulloch bar pics. It's a pretty cool bar. I would actually like to keep it as a keepsake, but another part of me say it should be on a 3-25 where it belongs. If you don't have a 3-25, please don't ask me to sell it to you. If anyone is going to hang this on a wall, it will be me lol. Notice the logo is upside-down when you spin the bar around to the opposite side.

I'm not seeing any pics on my end . What kind of bar is it? All I collect are the early McCulloch saws...3-25, 4-30, 49, 73, 77, etc... I find these old saws most easy to work on, run and maintain. Plus the design features and changes along the way are interesting to see. Anyway I'm guessing the old goose bar. Would love to find an early perforated on but you just don't see those at all...

Sent from my SM-T330NU using Tapatalk

 

[Sepia]

Yes bar has the McCulloch name within an oval, with 3 geese flying in the background. Not sure why you can't see the pics??
Just PM me if you are interested and I can send the pics to your email if you like.

 

[fossil]

Thanks. I just happen to have one of those in inventory. The trigger is thinner with a welded pivot pin that rotates in the housing. It was much harder to set off than my others - could be the design or the fact it is unused. Nonetheless I'm not sure what MAC was thinking with the change to the wider trigger shaped for the new style spring but without actually fitting the new spring. Ron

View attachment 570096 View attachment 570099 View attachment 570100

That one I have is a little harder to trip but not much difference. It's likely very "experienced".

It's quite a while since I tripped a brake cutting. Not much chance of doing it bucking wood.

 

[rwoods]

That one I have is a little harder to trip but not much difference. It's likely very "experienced".

It's quite a while since I tripped a brake cutting. Not much chance of doing it bucking wood.

That is what is so aggravating with mine. One fires at will. The other with the slightest touch - making bucking at the dogs impossible unless you hold the handle back with your hand. I have tied both back with two wraps of CAUTION ribbon which works until it stretches. Untested theory in using the tape is that it would still allow the brake to work in a kickback situation.

Ron

 

[fossil]

That is what is so aggravating with mine. One fires at will. The other with the slightest touch - making bucking at the dogs impossible unless you hold the handle back with your hand. I have tied both back with two wraps of CAUTION ribbon which works until it stretches. Untested theory in using the tape is that it would still allow the brake to work in a kickback situation.

Ron

Have you tried stretching the spring a bit to get more tension? I would suggest cutting the groove in the pawl a little deeper so it doesn't trip so easily. You have to be carerful that you don't cut it too deep or the brake band may drag on the drum. If you like making little parts, you might try making a pawl with a higher trip trip ledge which would give it a deeper groove in the off position.
Something is worn or the spring is too weak.

I have come across a number of Poulan 3400 - 4000 series where the paw is worn and the brake band drags. I made some new pawls and they work great now.
The nice thing about those brakes is you can adjust the amount of force it takes to trip them.

 

[rwoods]

Too problems - one is design and the other is wear related to the design. The newer generation "trigger" / pawl is wider - I assume to make the release of the handle easier with the larger bearing surface. The pawl fits the spring perfectly if the spring is behind the pawl but MAC didn't built them that way (at least none of mine). The pawl lays flat against the side of the brake as does the trigger end of the spring. This basically defeats the spring notch in the pawl. So when the pivot pin get loose the pawl will twist allowing the spring to slip off of it which in turn allows an easy fire and in some cases (mine) the inability to re-lock the pawl. I tore into my other brake tonight and discovered that it had the same problem - contrary to what I said last night. I took the one I worked on last night and ground some of the backside of the pawl so now I have only one washer. But nevertheless the pivot pin in neither will stay in, with or without the washers. Any thoughts? JB Weld? If I could make a new pawl it would be offset the thickness of the spring wire from the spring notch to the bottom so that the pawl would be stabilized against the brake housing while letting the spring do the same and sit behind the tip of the pawl. This could be done easily with a thin pawl like the originals, but its over my pay grade with the thick pawl and countersunk pivot pin.

The springs aren't weak. I have several dog and screwdriver holes in my hand tonight to prove it.

Ron

 

[rwoods]

I re-read fossil's post. We are talking about opposite ends of the pawl. I am talking about the spring end and he was talking about the handle / brake band end. Nothing on the spring end will affect the brake band until fired. Fiddling with the other end could.

Ron

 

[2broke2ride]

Anyone have the top half of the fuel tank for a Mac 440? Mine had a home in it that was sorta patched when I bought it. Wouldn't mind replacing it while it's apart if I can find it. Pic of the saw in question

 

[2broke2ride]

I am getting really frustrated with this saw[emoji35]. This is the above mentioned 440. If you've been following along it was acting weird. Not responding to throttle idling strange, unable to rev. But if I played with it I could get it to rev out and it would run and cut well. So I pressure tested the crankcase and found a leak at the reed plate. Though I had it. So I just got it back together. Made all new gaskets for it, re pressure tested and all good. It still acting the same!!!!! It will idle forever although rough and doesn't sound right. But when you hit the throttle there is no change!!!! No bog, no rev, there maybe is a slight change in pitch at the carb throats but that is it. And to make matters worse, I can't even feather it to rev anymore. I got it to rev out once and when it did it sounded great, had a nice burble unloaded and cleaned up and pulled good in the wood. I don't know I'm stumped. Crank seals are new, been through the carb three times although still waiting on a kit from sugar creek. Resealed the reed plate.
It almost acts like the reeds are acting as sort of a throttle plate and not opening of that makes any sense. Sorry for the novel. Hoping someone can help.

 

[happysaws]

I am getting really frustrated with this saw[emoji35]. This is the above mentioned 440. If you've been following along it was acting weird. Not responding to throttle idling strange, unable to rev. But if I played with it I could get it to rev out and it would run and cut well. So I pressure tested the crankcase and found a leak at the reed plate. Though I had it. So I just got it back together. Made all new gaskets for it, re pressure tested and all good. It still acting the same!!!!! It will idle forever although rough and doesn't sound right. But when you hit the throttle there is no change!!!! No bog, no rev, there maybe is a slight change in pitch at the carb throats but that is it. And to make matters worse, I can't even feather it to rev anymore. I got it to rev out once and when it did it sounded great, had a nice burble unloaded and cleaned up and pulled good in the wood. I don't know I'm stumped. Crank seals are new, been through the carb three times although still waiting on a kit from sugar creek. Resealed the reed plate.
It almost acts like the reeds are acting as sort of a throttle plate and not opening of that makes any sense. Sorry for the novel. Hoping someone can help.

Is the timing off?
I would check to see if the flywheel key is sheared or missing...

 

[2broke2ride]

I can't figure out how to post video for some reason. It used to be super easy. Something changed.

 

[2broke2ride]

Let's try this

 

[2broke2ride]

There that worked!!!! You can see what I got going on here. Not sure where to go with it.

 

[happysaws]

Let's try this

Wow... That's really weird.
Is the chain too tight?
Timing?
Is something rubbing on the sprocket, and preventing it from turning?
Take the clutch cover off, and try running it again.

 

[2broke2ride]

Unfortunately I've tried all that obvious simple stuff.....thank you for the suggestion though.
Cant run without the clutch cover, thats the recoil lol.