McCulloch Chain Saws

[heimannm]

ether - You cannot always take Acres information at face value, there are a few errors in his listings and even some of the saws with the same bore & stroke have very different port timing or other port variations which can make a big difference in performance.

Mark

 

[joeymt33]

I've ran a PM650 with a 24" 3/8 skip and it did ok but I'd much rather prefer my sp80 with a 24" 8 tooth full comp.


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[minosi]

Make sure you have the big end cap on the right way around it only fits one way

McBob

The rod cap is "cracked" and will only fit on one way as Bob and Lee describe...you can bolt in down wrong and maybe not notice.

There are "tabs" (little round castings) cast into the rod, they should go to the same side.

Make sure the crank bearings are seating perfectly as there should be no room (or very, very little) to move the crank side to side once the points box has been installed. It sounds like you have a lot of slop if the rod binds resting the saw on the side, forcing the rod to the edge of the journal. If you replaced the piston, did you install it on the rod the same way, with the same side of the rod facing the ex vs. intake? Little things like that can make a difference if the rod turned countless rev's oriented one way, then you turned it around.

Do a visual inspection on the sides of the rod itself, if it bound up while running, it will no doubt have left a rub mark on the rod. The "copper" appearance of the rod will be noticeably gone where it has rubbed....work that area with a flat file to fit.

My 797 had a little wear on the side of the rod, just removing the smallest fraction of material will gain you the clearance you need.

Nice project BTW

-Andy

 

[ozflea]

Homelitejim Considering they are basically the same saw probably not. Only difference I noticed between the 610 I had and a friends 650 was weight. You also have to remember at that time there where 4 or 5 saws badged differently but where essentially all the same innards. On e-bay I've seen a few montgomery ward (Sears), TYM and a few others all the same saw.

PM 650
ENGINE DISPLACEMENT:
3.7 cu. in. (60 cc)
CYLINDER BORE:
1.85 in. (47 mm)
PISTON STROKE:
1.38 in. (35 mm)
CYLINDER TYPE:
Aluminum with chrome plated bore
INTAKE METHOD:
Piston ported

PM 610
ENGINE DISPLACEMENT:
3.7 cu. in. (60 cc)
CYLINDER BORE:
47 mm
PISTON STROKE:
35 mm
CYLINDER TYPE:
Aluminum with chrome plated bore
INTAKE METHOD:
Piston ported

=================================================

There's a fair bit of difference between the PM610 and the PM650 Internally thin rings piston different exhaust port ............. the 610 was made to be a farm saw whereas the PM650 was meant to be the start of Mac's pro-saw range ..... so when the two saws are run side by side bar and chain being equal there's a fair bit of difference in performance

McBob

 

[joeymt33]

Another note, the PM610 with the flag brake handle had thin rings and the 610 with the wrap around brake handle had thick rings.

Like bob just said, those make a difference too.

I've had some of the early PM650 saws with the wrap around brake handle and they also had the thick rings.


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[Mo. Jim]

I found a rough looking PM 55 in my stash,would a 850 shortblock bolt in without a lot of modifications? This would be a sleeper rat rod GTG saw,this is a nos engine.I have three of them I have been hoarding along with a 700.

 

[Nogoingback]

Found the problem.

Think I found the problem with the crank binding issue I'm have with my kart saw. I pulled the saw apart planning to rotate the rod 180 on the piston to see if it made a difference. No visible wear on any parts so before pushing the wrist pin back in, I placed a straight edge across the flats on the rod with the bearing cap tightened back on and could see that the rod is bent. Don't think I did it but who knows. Kind of happy to at least find the likely cause of the problem.

Anybody have an extra usable 101 rod laying around that you wouldn't mind parting with?

Thanks for all the suggestions and info so far.

 

[cpr]

Think I found the problem with the crank binding issue I'm have with my kart saw. I pulled the saw apart planning to rotate the rod 180 on the piston to see if it made a difference. No visible wear on any parts so before pushing the wrist pin back in, I placed a straight edge across the flats on the rod with the bearing cap tightened back on and could see that the rod is bent. Don't think I did it but who knows. Kind of happy to at least find the likely cause of the problem.

Anybody have an extra usable 101 rod laying around that you wouldn't mind parting with?

Thanks for all the suggestions and info so far.

Glad you found it, now it gets tough. The rods are the scarcest part in the short blocks for these...

 

[ozflea]

Here are the pictures if the NOS 650 cylinder and a used 610 cylinder.

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That exhaust port on the PM650 was designed that way and called the "Q" port to soften the exhaust note

secondly the 650 had a larger ex port so tool steel rings were needed to stop rings becoming snagged

 

[joeymt33]

As you can see, the 610 also had it. As a matter if fact, all the 600 series saws I've ever ran across had it.


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[rwoods]

Think I found the problem with the crank binding issue I'm have with my kart saw. I pulled the saw apart planning to rotate the rod 180 on the piston to see if it made a difference. No visible wear on any parts so before pushing the wrist pin back in, I placed a straight edge across the flats on the rod with the bearing cap tightened back on and could see that the rod is bent. Don't think I did it but who knows. Kind of happy to at least find the likely cause of the problem.

Anybody have an extra usable 101 rod laying around that you wouldn't mind parting with?

Thanks for all the suggestions and info so far.

Just how bent is yours? I can't see a bend in mine but I can feel that the straightedge is not entirely flat on the wrist pin end of my rod - more noticeable on one side than the other. As to the cap being reversed - there is no way a reversal of mine could go unnoticed. Thanks, Ron

 

[Nogoingback]

The rod cap is "cracked" and will only fit on one way as Bob and Lee describe...you can bolt in down wrong and maybe not notice.

There are "tabs" (little round castings) cast into the rod, they should go to the same side.

Make sure the crank bearings are seating perfectly as there should be no room (or very, very little) to move the crank side to side once the points box has been installed. It sounds like you have a lot of slop if the rod binds resting the saw on the side, forcing the rod to the edge of the journal. If you replaced the piston, did you install it on the rod the same way, with the same side of the rod facing the ex vs. intake? Little things like that can make a difference if the rod turned countless rev's oriented one way, then you turned it around.

Do a visual inspection on the sides of the rod itself, if it bound up while running, it will no doubt have left a rub mark on the rod. The "copper" appearance of the rod will be noticeably gone where it has rubbed....work that area with a flat file to fit.

My 797 had a little wear on the side of the rod, just removing the smallest fraction of material will gain you the clearance you need.

Nice project BTW

-Andy

Think I have the problem figured, the rod is bent. The rod didn't actually contact the crank but the needles would start to slant downwards and then bind. Wouldn't do it while pushing the rod to the pto side. At least I got to here it run briefly.

 

[Nogoingback]

Just how bent is yours? I can't see a bend in mine but I can feel that the straightedge is not entirely flat on the wrist pin end of my rod - more noticeable on one side than the other. As to the cap being reversed - there is no way a reversal of mine could go unnoticed. Thanks, Ron

Didn't measure the gap under the straight edge but a lot of light can be seen through it. View attachment 306738

 

[promac850]

I bet if you got yourself a decent 1 or 2 ton arbor press, and an oxy/acetylene torch, you could warm it up enough to straighten it. I recommend that you then re heat treat it and shot peen it afterwards, though.

If it's a minor bend, someone out there can straighten it. A machine shop would be a good place to ask questions on straightening a connecting rod. Maybe it's something that they can tell you enough about, and something that you could do yourself.

Just talking out of my ass over here.

Edit: that is a real minor bend. Probably could be straightened without heat, which would remove the need for heat treating. Would still shot peen it afterwards, though.

 

[mactodd]

I got to play with this over the weekend in some 28" red oak that had been down a while.

 

[ethar]

Any one have a spare 600 series piston lying around or piston and rod. According to the pics I believe someone cut away the excess on my 610 at some point because it doesn't have the extra bit of metal on the port. I can see where the rings have snagged abit. Cylinder is smooth no burrs or scratches just on the piston itself. When you buy used saws unless you tear them down can never tell what has been done to them.

 

[promac850]

Any one have a spare 600 series piston lying around or piston and rod. According to the pics I believe someone cut away the excess on my 610 at some point because it doesn't have the extra bit of metal on the port. I can see where the rings have snagged abit. Cylinder is smooth no burrs or scratches just on the piston itself. When you buy used saws unless you tear them down can never tell what has been done to them.

I'll check with a source tomorrow.

 

[rwoods]

Didn't measure the gap under the straight edge but a lot of light can be seen through it. View attachment 306738

That gap looks parallel to me. Maybe the rod just needs to be flipped. My engine is in many pieces. If it still binds when I put it back together I am going to flip it to see if it makes any difference. Ron

 

[Busmech]

I bet if you got yourself a decent 1 or 2 ton arbor press, and an oxy/acetylene torch, you could warm it up enough to straighten it. I recommend that you then re heat treat it and shot peen it afterwards, though.

If it's a minor bend, someone out there can straighten it. A machine shop would be a good place to ask questions on straightening a connecting rod. Maybe it's something that they can tell you enough about, and something that you could do yourself.

Just talking out of my ass over here.

Edit: that is a real minor bend. Probably could be straightened without heat, which would remove the need for heat treating. Would still shot peen it afterwards, though.

I have had the same problem and successfully straightened it with a press without heat, it's still working a couple years later.

 

[promac850]

That gap looks parallel to me. Maybe the rod just needs to be flipped. My engine is in many pieces. If it still binds when I put it back together I am going to flip it to see if it makes any difference. Ron

Now that you mention it's parallel, that's probably why it's binding... needs to be flipped.

When I took the .020" over piston off of the connecting rod for my 790 build, I was anal about marking the rod and top of the piston as to which side faced where... no issues there.

Still got other issues to solve with that big monster Mac though...