MCCULLOCH The official McCulloch thread

[the 28inch mac man]

Looking for a little advice. Got the SP81 back together. Think its burning a little bar oil, but nothing serious.
Just cleaned the carb. 2 hours in NAPA brand carb cleaner, then 30 minutes in the ultrasonic with water temp about 40C/110°F.
New carb kit.
Metering lever is level with housing.
Tab is hooked in metering lever.
Black gasket to pump side, then teflon.
Thick gasket used with stamped steel cover.
Fixed hi jet carb.
Saw idles and accellerates fine.
Wont open up in the cut. Bogs if you dog in at all. Stalls the chain. Seems WAY too rich.
Blew through a tank of fuel.
Seemed to open up as it was running out of fuel.
Anything i can do to fix?

I would say the problem is the fixed man jet carb. Those things run great or they don't. The carb from the pm 700 should work fine. Btw you have a great saw if it is bulding close to 200 psi! I would call 160 psi good!

 

[the 28inch mac man]

McCulloch small spline drum to fit the 10/600 Series saws is 86948, Oregon PN 18459.

McCulloch large spline drum to fit the 10/600 Series saws is 86947.

I don't know of any small spline 3/8-8T but large spline 3/8-8T are readily available. I have a bunch...

Mark

Thanks again Mark for the info. The 8 tooth sprocket made a huge difference on the 7-10. That thing now cuts much more like a modern 70cc saw and I love it!

 

[Dream]

Hmm. Didnt think about the hi speed check valve.
How much pressure on the needle?

 

[Dream]

I would say the problem is the fixed man jet carb. Those things run great or they don't. The carb from the pm 700 should work fine. Btw you have a great saw if it is bulding close to 200 psi! I would call 160 psi good!

Yeah the piston/rings and cylinder are mint.
I might come back later and check the hi speed check valve if the PM700 carb doesnt work right.
I removed it and cleaned it, but didnt replace the disc and clip.
My dexterity with tiny parts isnt as great as it used to be.

 

[Steve]

Hmm. Didnt think about the hi speed check valve.
How much pressure on the needle?

7psi and it should hold steady. If it doesn't spray the carb with soapy water to make sure it isn't a gasket leaking.

 

[heimannm]

The high speed check valve doesn't really come into play at high speeds, it is there to prevent pressure in the carburetor from pushing fuel out the idle ports at low speeds flooding the engine. It is referred to as a high speed check valve since it actually closes the high jet (port)

I have several saws with the fixed H carburetors and they all do quite well when they operate with a load. The 10 Series saws in particular (PM55, SP80) do very well.

Sorry if I missed it, which carburetor on the SP81? I have had problems with the Tillotson models with the high speed governor that run excessively rich regardless of the H adjustment.

Mark

 

[the 28inch mac man]

The high speed check valve doesn't really come into play at high speeds, it is there to prevent pressure in the carburetor from pushing fuel out the idle ports at low speeds flooding the engine. It is referred to as a high speed check valve since it actually closes the high jet (port)

I have several saws with the fixed H carburetors and they all do quite well when they operate with a load. The 10 Series saws in particular (PM55, SP80) do very well.

Sorry if I missed it, which carburetor on the SP81? I have had problems with the Tillotson models with the high speed governor that run excessively rich regardless of the H adjustment.

Mark

Those tillotson carbs are brutal!

 

[JIMG]

I was running my 800 out in the woods recently, tuned it in the cut and worked all day. When I got home I realized the high jet was only about a 1/4 turn out. I assumed it should be in the vicinity of one turn out on both. Went out to my testing log and made a couple cuts with the high at 1 out. It would not clean up in the cut until it was back where I had it at 1/4 out on the high jet.
Took carb apart, nothing was amiss that I could see, metering arm height was set right with my Z setter thingy.
What to do?

 

[the 28inch mac man]

I was running my 800 out in the woods recently, tuned it in the cut and worked all day. When I got home I realized the high jet was only about a 1/4 turn out. I assumed it should be in the vicinity of one turn out on both. Went out to my testing log and made a couple cuts with the high at 1 out. It would not clean up in the cut until it was back where I had it at 1/4 out on the high jet.
Took carb apart, nothing was amiss that I could see, metering arm height was set right with my Z setter thingy.
What to do?

Is it a zama carb? If so, I would put a walbro sdc on it.

 

[hacskaroly]

I am working on a Mac 10-10, the saw had been sitting for a while and fuel, oil and carbon solidified the piston in the cylinder. After spraying penetrating oil, picking out what I could and some selective whacking for about 2 hours, I was able to free the piston from the cylinder. It looks like a chunk of the top ring broke off and wreaked some havoc. Luckily the cylinder is not scorred, just has some carbon crud at the top and some light surface rust in the transfers. What is the best way to get rid of the rust or should I just go ahead and run the saw and the gas/oil and heat will take care of it?


Also, how do you line up the rings in this piston, I didn't see any pins anywhere to align to. Also, there are no cir-clips I could see holding the wrist pin in, is it just tapped into place? This is much different configuration that what I have seen before.



Also, has anyone purchased the McCulloch 10-10 piston 1 3/4", Gasket Set, Crankshaft Seals and Bearings on eBay by Lil' Red Barn Power Equipment Supply, if so, what did you think of it, did it work for you?

Duke's has a kit too, but without the piston.

​

 

[nbbt]

Picked up a PM700 today. Seems to have good compression. It will need a good cleaning and few items attended to b-4 it will be put into service.

.


The easy to see attention items so far include, but I'm sure not limited to are,
1) Needs a new air filter.
2) repair or replace the filter cover
3) very possible that the plug wire could use replacement.
4) The black plastic sawdust guard on the flywheel side in the starter cover is missing a section.
5) And some of the usual suspects for a saw that may have been sitting for a while.
6 And a general cleanup.

 

[Dream]

The high speed check valve doesn't really come into play at high speeds, it is there to prevent pressure in the carburetor from pushing fuel out the idle ports at low speeds flooding the engine. It is referred to as a high speed check valve since it actually closes the high jet (port)

I have several saws with the fixed H carburetors and they all do quite well when they operate with a load. The 10 Series saws in particular (PM55, SP80) do very well.

Sorry if I missed it, which carburetor on the SP81? I have had problems with the Tillotson models with the high speed governor that run excessively rich regardless of the H adjustment.

Mark

Mark, it is a Walbro SDC51.

 

[the 28inch mac man]

I am working on a Mac 10-10, the saw had been sitting for a while and fuel, oil and carbon solidified the piston in the cylinder. After spraying penetrating oil, picking out what I could and some selective whacking for about 2 hours, I was able to free the piston from the cylinder. It looks like a chunk of the top ring broke off and wreaked some havoc. Luckily the cylinder is not scorred, just has some carbon crud at the top and some light surface rust in the transfers. What is the best way to get rid of the rust or should I just go ahead and run the saw and the gas/oil and heat will take care of it?
View attachment 434384

Also, how do you line up the rings in this piston, I didn't see any pins anywhere to align to. Also, there are no cir-clips I could see holding the wrist pin in, is it just tapped into place? This is much different configuration that what I have seen before.

View attachment 434385

Also, has anyone purchased the McCulloch 10-10 piston 1 3/4", Gasket Set, Crankshaft Seals and Bearings on eBay by Lil' Red Barn Power Equipment Supply, if so, what did you think of it, did it work for you?

Duke's has a kit too, but without the piston.

​

You could clean those transfers out with a small wire wheel on a die grinder. My under standing is that the wrist pin is pressed into the rod with the bearings pressed into the piston. I would buy a good used piston and rod rather than go for a after market piston. That cylinder looks good.

 

[the 28inch mac man]

Picked up a PM700 today. Seems to have good compression. It will need a good cleaning and few items attended to b-4 it will be put into service.

View attachment 434387.
View attachment 434388
View attachment 434389
The easy to see attention items so far include, but I'm sure not limited to are,
1) Needs a new air filter.
2) repair or replace the filter cover
3) very possible that the plug wire could use replacement.
4) The black plastic sawdust guard on the flywheel side in the starter cover is missing a section.
5) And some of the usual suspects for a saw that may have been sitting for a while.
6 And a general cleanup.

Not a bad looking pm700!

 

[heimannm]

hacskaroly - The early 10 Series saws had round exhaust ports and did not use pinned rings. I try to locate the ring ends away from the ports and transfers and 90-120° apart but I don't think it really matters too much as they rings will likely migrate when the engine is running anyway. The LRB pistons have been hit or miss, in any case don't use their wrist pin as they are too small and won't fit the rod correctly. The wrist pin is a pressed fit in the rod and that's the only thing to keep it in place. I've found an overnight soak in some of the commercial cleaners (Mean Green, Purple Power, Super Clean, etc.) does wonders at removing accumulations from the cylinders.

Dream - the 51 is a fixed H jet carburetor, but there were different jets available depending on your altitude. It is possible you need to change the jet which theoretically involves pressing the old one out and the new one in. I thought I had some around at one time but I'd really have to do some searching to find them again. There's probably a service bulletin that describes the various options but I don't think I could find that again very easily either.

nbbt - I probably have all the bits you need if you can't find them elsewhere. I certainly will have the AF, AF cover (may not have the PM700 decal), and sawdust screen. The plug wire should unscrew from the coil but sometimes they twist off in the socket. Some careful work with a hollow "screw extractor" bit can remove the remnants of the wire if needed.





Mark

 

[hacskaroly]

You could clean those transfers out with a small wire wheel on a die grinder. My under standing is that the wrist pin is pressed into the rod with the bearings pressed into the piston. I would buy a good used piston and rod rather than go for a after market piston. That cylinder looks good.

Thanks, I will give it a try. I don't have a die grinder, but I do have a Dremmel so I will give that a shot. I found a pin/bearing extraction/installation tool on Duke's Saw Shop website that is used for these, found it after posting, now I understand why these have two roller bearings and no clips! Why would you go with a used vs. aftermarket piston (honest curiosity here). The top of the piston is beat to crap, I expected more damage in the cylinder, pleasantly surprised at the good condition it is in.

The plug wire should unscrew from the coil but sometimes they twist off in the socket. Some careful work with a hollow "screw extractor" bit can remove the remnants of the wire if needed.

This is good to know, I forgot to mention that my coil wire is broken off below the lip. I will have to look at getting a hollow screw extractor!

Does it take any special lead? I have seen a few on eBay for about $25 (NOS McCulloch I believe).

 

[the 28inch mac man]

Thanks, I will give it a try. I don't have a die grinder, but I do have a Dremmel so I will give that a shot. I found a pin/bearing extraction/installation tool on Duke's Saw Shop website that is used for these, found it after posting, now I understand why these have two roller bearings and no clips! Why would you go with a used vs. aftermarket piston (honest curiosity here). The top of the piston is beat to crap, I expected more damage in the cylinder, pleasantly surprised at the good condition it is in.


This is good to know, I forgot to mention that my coil wire is broken off below the lip. I will have to look at getting a hollow screw extractor!

Does it take any special lead? I have seen a few on eBay for about $25 (NOS McCulloch I believe).

A dremmel should work. The reason I would go for a used piston(and rod) is for 2 reasons. First oem mcculloch parts will be much higher quality than the best aftermarket stuff. Second people who sell used pistons usaly sell them as piston rod assembles so you don't have to worry about pressing out/in the pin and bearings. There are some really nice used piston/rods on ebay for a good price.

 

[Dream]

Picked up a PM700 today. Seems to have good compression. It will need a good cleaning and few items attended to b-4 it will be put into service.

View attachment 434387.
View attachment 434388
View attachment 434389
The easy to see attention items so far include, but I'm sure not limited to are,
1) Needs a new air filter.
2) repair or replace the filter cover
3) very possible that the plug wire could use replacement.
4) The black plastic sawdust guard on the flywheel side in the starter cover is missing a section.
5) And some of the usual suspects for a saw that may have been sitting for a while.
6 And a general cleanup.

On the coil wire, if its just the insulation and the wire isnt broken, ive repaired several with Scotch brand high voltage insulating tape.
Ill have to get the info on it, but its something ive used for many years as an electrician.
One wrap is good for 10,000 volts, so it works well where the insulation has gotten pinched or worn going thru covers etc.
can be covered with heat shrink. I usually just cover with a wrap of Scotch super 33 electrical tape.

 

[hacskaroly]

The reason I would go for a used piston(and rod) is for 2 reasons. First oem mcculloch parts will be much higher quality than the best aftermarket stuff. Second people who sell used pistons usaly sell them as piston rod assembles so you don't have to worry about pressing out/in the pin and bearings. There are some really nice used piston/rods on ebay for a good price.

Sound solid to me. I was looking at the eBay listings...some of them have fuzzy photos...hard to tell if there is any scorring or not. I did notice that most of the pistons come with the rod, I can see how that would be easier to sell than trying to punch out the pin. Thanks for the info!

 

[hacskaroly]

One wrap is good for 10,000 volts, so it works well where the insulation has gotten pinched or worn going thru covers etc.
can be covered with heat shrink. I usually just cover with a wrap of Scotch super 33 electrical tape.

Sounds like something I need to add to my bench, sometimes its impossible to get some heat shrink on the line, but sounds like this tape will do the trick!