McCulloch Chain Saws

[homelitejim]

I was going to point out the operator presence lever but I didn't want to sound like a purist.

 

[Eccentric]

Is the DSP valve and the compression relief the same thing? I see a lot of talk about them and am curious.

Ray

Same thung Ray. DSP was just McCulloch's name for it.

I was going to point out the operator presence lever but I didn't want to sound like a purist.

Talking about the SP-81 Jim? I've seen an SP-81 with the op-pres/throttle lock instead of the button throttle lock. May have been an SP-81E.

 

[rwoods]

Is the DSP valve and the compression relief the same thing? I see a lot of talk about them and am curious.

Ray

Yes.

I was going to point out the operator presence lever but I didn't want to sound like a purist.

Now now. You should know by now not to be too dogmatic about MACs as they made lots of versions. The SP81E has the operator presence lever. Not sure about the original SP81 as I don't have an IPL but they made this model into 1977 and I believe the OPL was standard at that time. I am guessing that they were like the 125C - the later models have it and the earlier models don't. Ron

I see Aaron is quicker at the draw than I.

 

[heimannm]

DSP = De Stroking Port; the original McCulloch design on the 795/795 and CP70 type saws had the valve located somewhat down from the top of the combustion chamber so it would vent some of the compression up to the point the piston "closed" the port. The DSP was manually operated, with a lever and a latching mechanism to keep it closed when the engine was running. The 3-10, 5-10, 6-10, and 10 Series Electric Start models all had a similar DSP valve that was spring loaded so there was no need to latch it closed.

Later on, the Pro Mac 805 and 850 had the pop up type compression release located on the cylinder below the top of the combustion chamber, as did the 600 series (650, 655). The PM800 had the "Q" port, a notch in the top of the exhaust port that eased the starting since the 800 did not have the pop up type valve. The service bulletin on the "Q" port says it eased starting, reduced noise, and increase power; sounds like the McCulloch engineers were reading the J.C. Whitney catalog.

Other 10 Series saws (7-10, 10-10S, PM55/555/570, PM60, SP60, SP70) had the compression release valve in the "head" as did the large SP models, SP105 and SP125.

More than you ever really wanted to know...

Mark

 

[rwoods]

To clarify: The Sp80, SP81 and original PM850 had the DSP in the head similiar to the later models of the smaller ten series; there is a cleanout in the side of the cylinder. The remaining 82cc MACs (PM800, PM805, Super PM850, PM8200 and DE80) had the q port design. In addition some of these had the DSP as well; it was located at or about the same place as the clean out in the earlier models. Disclaimer: other than pictures I have never seen a Super PM850 but I have seen cross references to its cylinder with the 800 and 805. Ron

 

[heimannm]

I don't have an 805, 850, 8200, or DE80 (yet) but the IPL's that I have show the DSP valve used in the 805 and DE80 in the cylinder (clean out position) not in the head. The 850 and 8200 both show "clean out hole" plugged, the 850 with a 10-24 screw and the 8200 with a 3/8 special which would match the pop up type DSP valve. Other 850 IPL's show a DSP valve, or plug, or both. One 850 IPL from KTOutdoors shows the DSP valve in the head like the SP80/81/81E. The Super 850 IPL shows a 3/8 special plug like the 8200.

I have several different PM800 IPL's, some are without DSP valve, some show both the valve and the plug, but all are in the cylinder (clean out) position, none in the head.

Mark

 

[bob15]

My PM800, PM805(parts saw) and the DE80 are all in the same in regards to DSP location. My PM8200 would be in the same spot, but isn't drilled, ignore the bar cover in the picture as it isn't original. I have another saw PM800 that was drilled for the DSP, but was plugged. The DSP or plug is used to hold the muffler brace on.

The PM800, PM805, PM8200 & DE80 all have the impossible to find coarse thread DSP. I am not sure on the PM850, but I believe it is the same as the SP60, SP70, SP80, SP81, SP105, SP125 & PM570, which is the fine thread, readily available DSP.

 

[rwoods]

My PM800, PM805(parts saw) and the DE80 are all in the same in regards to DSP location. My PM8200 would be in the same spot, but isn't drilled, ignore the bar cover in the picture as it isn't original. I have another saw PM800 that was drilled for the DSP, but was plugged. The DSP or plug is used to hold the muffler brace on.

The PM800, PM805, PM8200 & DE80 all have the impossible to find coarse thread DSP. I am not sure on the PM850, but I believe it is the same as the SP60, SP70, SP80, SP81, SP105, SP125 & PM570, which is the fine thread, readily available DSP.

The original PM850 is the same as the SP81 - fine thread - small flat plastic button. The coarse thread PM800 etc. DSPs have a plastic cap/button similiar to the SP125. The intake port is also bigger on these saws than the SP80, SP81 & the original PM850. Same basic casting but with a slot cut out. Here are some pictures I have posted before; you can see the early model cleanout (small hole) and late model DSP location (big hole) to the upper left of the intakes in the second picture:

Close up of intake "slot":

Comparison of intakes - SP81/PM850 on left PM800, 805, DE80, 8200 & Super 850 on right:

Ron

Comparison of exhaust ports - SP81/PM850 on left PM800, 805, DE80, 8200 & Super 850 on right:

 

[mactodd]

DSP = De Stroking Port; the original McCulloch design on the 795/795 and CP70 type saws had the valve located somewhat down from the top of the combustion chamber so it would vent some of the compression up to the point the piston "closed" the port. The DSP was manually operated, with a lever and a latching mechanism to keep it closed when the engine was running. The 3-10, 5-10, 6-10, and 10 Series Electric Start models all had a similar DSP valve that was spring loaded so there was no need to latch it closed.

Later on, the Pro Mac 805 and 850 had the pop up type compression release located on the cylinder below the top of the combustion chamber, as did the 600 series (650, 655). The PM800 had the "Q" port, a notch in the top of the exhaust port that eased the starting since the 800 did not have the pop up type valve. The service bulletin on the "Q" port says it eased starting, reduced noise, and increase power; sounds like the McCulloch engineers were reading the J.C. Whitney catalog.

Other 10 Series saws (7-10, 10-10S, PM55/555/570, PM60, SP60, SP70) had the compression release valve in the "head" as did the large SP models, SP105 and SP125.

More than you ever really wanted to know...

Mark

In addition to those, the Super 2-10 Automatics also had the spring loaded DSP.

 

[rheima]

DSP valve

Thanks guys for all the information. That is what I like about this site----all the info and sometimes so much more! Thanks little brother Mark too!

 

[Eccentric]

A quick McGeardrive queston...

Can an auto oiler pump for/from a later gear drive McCulloch such as a 640, 890, or 895 be swapped onto an earlier gear drive such as a 1-60 series? If so, what parts are needed?

 

[leeha]

Can an auto oiler pump for/from a later gear drive McCulloch such as a 640, 890, or 895 be swapped onto an earlier gear drive such as a 1-60 series? If so, what parts are needed?

My first thought was yes you can. But i gave it some
thought and i don't think you can. If the cover where
the pump goe's is a 3 bolt cover then the gearcases
will not be drilled for the oil passages. If the cover is
a 4 bolt then they might be drilled but not all of the
4 bolt styles i have seen were drilled. If drilled then
you will need the pump and the shaft that drives it.



Lee

 

[Eccentric]

Thanks for the info Lee. Just what I neded.

 

[heimannm]

The boss where the cover or oil pump would mount is different on the earlier (non-automatic oil pump) versions compared to the later models with the oil pump. The oil pump would not have any place to mount on the older versions. No doubt with McCulloch there were probably some "transition" saws built with the boss and hole locations for the automatic oil pump but fit with the simple cover, but I don't think I have any like that.

Mark

 

[DFK]

Can a chain break be installed on McCulloch 10-10 Automatic???

I know almost nothing about repairing / working on chainsaws.
Think I am going to buy a running 10-10 for $25.00 but would like a chainbreak on it.

Have seen some with and some without chainbreaks.

Thanks
David

 

[Warped5]

Can a chain break be installed on McCulloch 10-10 Automatic???

I know almost nothing about repairing / working on chainsaws.
Think I am going to buy a running 10-10 for $25.00 but would like a chainbreak on it.

Have seen some with and some without chainbreaks.

Thanks
David

Yes, they can.

Many of the later saws in the Mac 10-series were equipped with brakes. All you need to do is locate a parts saw or a parts hoarder to get one. I have seen them on eBay, but they are priced a bit high IMHO.

I'd go the parts saw route and keep the spare parts for future Mac projects. Yes, there will be more. :hmm3grin2orange:

 

[DFK]

Thanks Warped5:

I am wanting to learn to " work on chainsaws ". My wife thinks I am nuts.
10 years from retirment. Need to find something to keep me busy after I retire.
I know 10 years is a long time.... But, I learn slow...:msp_tongue:

As I understand it the 10-10 saws are simple to work on and lots of parts are still around.
So, I figured a 10-10 would be a good first saw to learn the basics on.

Plus, Now that I have found AS, I got all you guys to help.

Wish I had not parted with the old Homie XL when it messed up.
I show-nuff wish I had not parted with my Partner 500 when it fried it's piston.
I could just kick my on butt for that.

David

 

[Overtrained]

As I understand it the 10-10 saws are simple to work on and lots of parts are still around.

Yes this is true, most of the 10 series saw parts are all interchangeable. I went nuts on a 2-10 about 20 pages back and it has parts from a bunch of different saws. Good luck with your projects.

 

[ChainsawmanXX]

D36 block in a 250 chasis, working some carb issues. Only stays running for alittle, but its pullong fuel? Also has a good carb kit in it? Ill have to work on it. I also polished the ports up alittle on the cylinder.

 

[Eccentric]

Loose/leaking fuel line in the tank, or maybe the pump section carb diaphragm/gasket installed in wrong order.