McCulloch Chain Saws

[2broke2ride]

So whats the deal with condensers? Do I need to get one for this saw specifically or can I use any one and just splice wires? Sorry, electronics are not my strongest point.

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[brandonstc6]

Thanks for the help, I have never experienced a bad condenser so I have no idea how it would act. Might be worth swapping a known good one. But not looking forward to pulling the flywheel from another saw[emoji35]

In my experience a bad condenser will make an engine run like crap. One day I got my 1949 ford pickup out to drive it around the block and it ran horrible and barely made it 30 yards. I popped the distributor cap off, replaced the condenser and it then ran perfect.


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[heimannm]

Most any condenser for a small engine will work, all of the McCulloch ones I have tested are in the range of 0.22 micro farads.

While charging them to 400 volts may be more definitive, I think you will find the test Tim describes as being quite good for our purposes.

Mark

 

[2broke2ride]

Thank you gentlemen

 

[Brian Thacker]

I had one of my PM6's to not run reliably, it would fall on it's face when you tried to rev it up. I kept thinking it was the carb. I was working on it one night and took my drill and started turning the motor over and watching the plug for fire. It would fire at low RPMs and as I would speed the drill up it would start miss firing until it almost stopped firing at full speed on my drill. I replaced the coil thinking that was it but was not, then changed the cap and that was not it. I started looking at the points and the spring was almost against the base plate. What I found was the point spring was almost touching the base plate and I think what was happening was when the RPMs got up the spring would start touching the base plate more and more killing the fire. I think what I done was when I was installing the points as I tightened up the bolt that has the spring under it and has the cap and the wire going to the coil the spring cocked just enough to let it almost touch. I also took my meter and hooked between the point output and ground and removing the wire from the coil going to the points and on omes scale I turned the motor over by hand and you could see it make and break at several places as you turned the motor over instead of just once. I took a piece of mylar from I think a power transistor or maybe a triac and placed it between the spring and the base plate so it would not happen again and aligned the spring up a little better. The clearance on those small points was not much so the mylar will always keep it from touching again.

Brian

 

[2broke2ride]

I had one of my PM6's to not run reliably, it would fall on it's face when you tried to rev it up. I kept thinking it was the carb. I was working on it one night and took my drill and started turning the motor over and watching the plug for fire. It would fire at low RPMs and as I would speed the drill up it would start miss firing until it almost stopped firing at full speed on my drill. I replaced the coil thinking that was it but was not, then changed the cap and that was not it. I started looking at the points and the spring was almost against the base plate. What I found was the point spring was almost touching the base plate and I think what was happening was when the RPMs got up the spring would start touching the base plate more and more killing the fire. I think what I done was when I was installing the points as I tightened up the bolt that has the spring under it and has the cap and the wire going to the coil the spring cocked just enough to let it almost touch. I also took my meter and hooked between the point output and ground and removing the wire from the coil going to the points and on omes scale I turned the motor over by hand and you could see it make and break at several places as you turned the motor over instead of just once. I took a piece of mylar from I think a power transistor or maybe a triac and placed it between the spring and the base plate so it would not happen again and aligned the spring up a little better. The clearance on those small points was not much so the mylar will always keep it from touching again.

Brian

I think I have something similar happening here. Gonna grab my fluke from work today and check it out.

 

[Brian Thacker]

This one had me scratching my head until I finally decided to look at the fire and it told the story.
Brian

 

[PogoInTheWoods]

So on a slightly different note..., I'm about to put my PM8200 back together with the original piston. Not much choice. Soaked it in Berryman's for two days hoping to loosen up the impregnated gunk and that worked well. Since there wasn't actually any transfer damage (just abrasive damage) it was a matter of knocking down high spots and smoothing without getting overly aggressive and removing too much material. A kind member from another forum sent me some various sized rolls of lapping paper measured in micron grit for the smoothing. I wet sanded with kerosene using the 20 grit (finest of the lot) and it slowly began to come around. Needed some very delicate filing at the top ring land and edge of the crown but everything else was done with the super fine lapping paper. (Thanks, Al.)

Biggest issue of the whole process was getting the piston off the rod. As most know, this saw used Mac's later three piece crank design with circlip captive wrist pin for the small end. And when I say captive, I mean captive. No ears on the circlips and no notch in the pin boss to pop them out. After several attempts at getting under the ends of the clips using pics without success I went ahead and notched the bosses. Didn't want to damage the clips since I figured I'd need to re-use them. Made it easy. Getting the wrist pin out was a whole other story. Seems as though it was pressed in and didn't even need the clips. Had to heat up the bosses pretty good and still use my arbor press to get it out. Will definitely need to chill the pin and heat the piston to get it back in.

Anyway, the pics...

The damage.



The likely cause.



Before / After








​

Still enough in the way of machine marks to keep me from worrying too much about excessive slap though the exhaust side is a little more suspect. We'll see.

​

I may also flatten the crown a hair to get the edge back. Got slightly rounded over working the top ring land area. Not sure if it makes any difference either way at this point.

​

So there ya have it. I'm convinced the lousy sealing job and possibly the type of sealant(s) caused the piston damage..., almost like two types of sealants were used. One was more of a silicone type and the other more like a varnish or shellac. This last pic is of another PM8200 with a damaged piston. Looks all too familiar and I'll bet more failures occurred than didn't with these saws due to atrociously sloppy short block assembly and the weird sealant combination. BTW, my cylinder will clean up like new. At least they had the plating right.

​

​

 

[PogoInTheWoods]

And a short follow up...

After some Berryman's Dip and a little brushing the combustion chamber cleaned up nicely. I didn't soak the whole cylinder for fear of the Berryman's eating the impulse barb seal. The streaking is from the sealant and should clean right up anyway, though. Some on the intake side as well.

And the notch in the pin boss...

​

 

[heimannm]

The barb for the impulse is basically a press fit, I suppose the sealant helps keep in in place but it is mostly mechanical. I had one bad SP 105 or 125 cylinder soaking for weeks and the impulse barb was still quite secure, not so much for some of the old paint...

Mark

 

[PogoInTheWoods]

Was a bit gun shy from my recent SP81 'loose barb' experience, though that wasn't a terribly difficult fix. Think I just used red Loctite.

 

[heimannm]

I have even used Indian Head with good results, just takes a long time to cure.

Mark

 

[2broke2ride]

Well it's official....... the monster lives!!!!!! The 440 now runs and cuts wood. The thing really rips with the 3/8" Stihl skip tooth I put on that monster bar plus I'm running an 8 pin rim. It still needs a bit of fine tuning but all in all it was a success!!!! I am not 100% sure what fixed it, I think in was a combination of things but the most recent ignition problem was the points not reliably making good contact. I am super stoked!!!! Now I gotta put the 380 back together that I was robbing parts from[emoji53]

 

[Brian Thacker]

Well it's official....... the monster lives!!!!!! The 440 now runs and cuts wood. The thing really rips with the 3/8" Stihl skip tooth I put on that monster bar plus I'm running an 8 pin rim. It still needs a bit of fine tuning but all in all it was a success!!!! I am not 100% sure what fixed it, I think in was a combination of things but the most recent ignition problem was the points not reliably making good contact. I am super stoked!!!! Now I gotta put the 380 back together that I was robbing parts from[emoji53]

Congratulations!!!

Brian

 

[fossil]

Need some advice PM700

I'm getting a few saws in good working order for the NY GTG.
I have a fuel tank leak. That's easy to fix. The rear part of the tank cover which covers the carb box was sealed with something that looked like silicone or some other caulking material. It came off in pieces so there's no chance of using it again.

Suggestions as to what would be suitable as a sealer for this area would be appreciated.

 

[Brian Thacker]

On ebay I see the seals for sale. Myself I just use a piece of cork gasket material that you can get at any auto parts store and silicone sealant and don't ever have a problem. I did learn the hard way to use the cork gasket material. I cracked a tank. It needs something in their to take up the space.
Brian

 

[PogoInTheWoods]

Assuming you're using a gasket for the tank, I'd use a bead of any rubberized and easily removable sealer for the rear just in case it has to come apart again.

I 'd certainly stay away from goo that hardens and adhesive stuff.

 

[heimannm]

If I can find your address Tim I can send some of the original sticky caulk they used if you think Canadian Customs will let it past the border.

I also have some double sided sticky foam tape ones in the attic that came in a large collection of parts I picked up, I can toss those in as well and let you be the guinea pig.

Mark

 

[fossil]

On ebay I see the seals for sale. Myself I just use a piece of cork gasket material that you can get at any auto parts store and silicone sealant and don't ever have a problem. I did learn the hard way to use the cork gasket material. I cracked a tank. It needs something in their to take up the space.
Brian

Thanks Brian.
I was meaning the rear part that surrounds the carb box. The gap was filled with some type of RTV type caulk keep dust out of the carb box.
My older 10 series saws seem to have a tight fit there. This 700 is a late one.

I think I solved it though. I found some yellow felt and cut some pieces to fill that gap. It should work well.
The tank gasket was in pretty good shape but really dry. I coated both sides with Motoseal which has worked well for me in the past.

 

[heimannm]

I will still send some sticky stuff just in case you decide to make it like the original...

Mark