McCulloch Chain Saws

[super44]

Anyone get pictures of the racing? We were unable to be there Saturday to see it.

 

[heimannm]

Kris always takes a lot of photos, I will see if I can get them from him and post a few.

I didn't take any except for Eric's Super 7-10 cover and the time sheets...

Mark

 

[fossil]

How did you do?

 

[bbrown549]

Anybody happen to know what idle and max rpm specs are on a Pro Mac 800?
Thanks,
Britt

 

[heimannm]

Anybody happen to know what idle and max rpm specs are on a Pro Mac 800?
Thanks,
Britt

Idle speed is slow enough to keep the chain from spinning, maximum RPM is just a little burble (4 stroke) WOT out of the wood. Read a few pages back and you will find some recent details in a post by Ron Woods I think, some saws were happy between 10,000 and 11,000 RPM.

How did you do?

All the McCullochs and the Poulan 4900 were running well, chains were sharp, I collected a few more plaques to hang in the museum.

Mark

 

[heimannm]

I receive a package from Kevin (2broke2ride) today with the brown Timber Bear. I thought I'd give it a thorough examination and a good cleaning.



After supper I wanted to check on one of the threaded holes for the coil mount, screw came out hard with some aluminum attached. I ended up drilling it out and installing a helicoil. One thing led to another and low and behold...





Thanks again Kevin for working with me on adding one more interesting model to the collection. I will get yours sent out tomorrow.

Mark

P.S. Here are the two latest 600 Series models, I think I will leave the Total bar on the 3720 for now to compliment the Total bar on 3420.

 

[2broke2ride]

Wow Mark, looks great. I guess you really did take her down for cleaning lol. Im proud to be able to contribute to the collection!!!
What was your overall assessment? I thought it seemed like a relatively low hour saw, and it didnt get much use while it was in my care.
I got it from my old boss, and my understanding was that he bought it new to clear the lot where he built the shop and never used it again after that.

 

[heimannm]

There was one screw missing, the grommet for the choke was damaged, and there was a fair bit of oily sawdust built up. Compression is still over 160 PSI and everything seems to be in very good condition including the chain catcher...first saw I have worked on lately that the chain catcher was not badly mangled. The paint looks good, I really like the color of the clutch cover.

Mark

 

[2broke2ride]

BTW Mark, keep that 4-30 on mothballs for me [emoji12] wink wink nudge nudge lol.

 

[PogoInTheWoods]

Anybody happen to know what idle and max rpm specs are on a Pro Mac 800?
Thanks,
Britt

Been wondering that for a long time myself and kept getting the "tune by ear" advice..., which is hardly a specification. And I generally do tune by ear, but also like to know what the recommended limits are when it comes to the top end so I can occasionally put a tach on things to keep me honest (and out of trouble sometimes). Most Mac service manuals even suggest tuning for "best performance" rather than by the sound of the saw. Guess they coulda been a little more vague, but it's pretty hard to miss the 4 stroking and pretty easy to hear when you're past it. You want to be a hair rich with these saws to get the max out of the power band vs. running a little leaner for the chain speed anyway. If you tune in the wood for "best performance" you'll likely be just a hair rich -- same as you would tuning a hair rich by ear after becoming familiar with a particular saw. On the other hand, just tuning a saw by whatever given method and calling it "tuned" is technically a fallacy by any means except when "tuned for the particular operating conditions" within the manufacturer's suggested recommendations unless modified to perform otherwise. Folks can argue that all day long, but there's a reason manufacturer's publish such specifications..., which is SO WE KNOW WHAT THEY ARE! Some 2 cycle tuning procedures even rely on specific adjustments in a particular sequence using a tach to properly set up the jet interaction for optimum performance. Smaller displacement machines like weedeaters, blowers, and other homeowner OPE come to mind there.

But long winded post longer, and to get as close as possible to answering the question, I've yet to find a published specification for idle speed and max allowable RPM for any 82cc Mac except the PM8200 at the bottom of the attached file. Considering the similarities among the 82cc 10 series Macs, one could presumably surmise that the 2800rpm idle spec and the 12,000rpm top end spec would apply across all models. It would be worth noting that heat dissipation rather than mechanical limitation would be the likely factor in determining their comfort level with the 12,000rpm number considering 11,500rpm seems to be the norm for other 10 series saws. Maybe they felt the larger canister muffler allowed another 500rpm's worth of heat dissipation? Who knows. Also of note is the rather curious 32:1 mix ratio for the PM8200 which may play into it, though that's not the only oddity found in the publication and could be a misprint.

Another possible reason for the non-existent top end specs could have been the public relations angle of not providing specifications which could have been viewed by competitors as negative limitations on the overall performance potential of the McCulloch brand in general. After all, some pretty crazy rpm's were being cranked out of McCulloch engines back in the day for both kart and saw racing (and still are in some circles), but certainly wouldn't have applied to or have been recommended for actual chainsaw use.

All the above rambling aside, bottom line for a stock saw doing typical work with reasonable performance expectations is tune for the general conditions according to its published factory recommendations and limitations..., except Macs, of course. LOL

BTW, I tuned my PM800 by ear out of wood and it tached at just under 12K..., and it's right on the top edge of 4 stroking running 91octane E-free with Stihl HP Ultra at 40:1. Very strong in red oak just as it is running a 24" full comp chisel b/c setup.

 

[heimannm]

McCulloch issued a Service Bulletin recommending the use of 32:1 in the 82cc models. I think they were so close to the edge with the porting on those saws, and the way people found they could lean them out and really get them to scream that adding some oil to the mix was needed to prevent scored cylinders and pistons.

Curious point but if you simply change the fuel mixture from 40:1 to 32:1 without adjusting the carburetor, you are actually running a leaner mixture (less fuel per unit of air).

Many of the SP and PM models came with a fixed "H" jet in the carburetor to prevent overzealous tuners from running them too lean. In my experience, those saw all have a lot of 4 stroke and require pretty substantial loading to get them to clean up in the cut. For saw that I take out to harvest wood, I don't mind the fixed H jet at all since they significantly reduce the chances of me running the saw too lean.

Sorry Poge, I guess it was you and not Ron who posted the set up specs...

Mark

 

[PogoInTheWoods]

Good point on the carbs. Would be interested to know where some of the fixed jet 82cc saws actually max out. Don't have one here to check since converting my SP81.

 

[rwoods]

With no chain, Brian and I were between 12,300 and 12,900 on our 800s and 12,500 on a PM850. Brian later melted the piston on the 12,900 saw. I don’t have a tach so I don’t know how much to deduct for a spinning chain.

Both the operator’s manuals for the 850 and the 800 say to adjust the idle so the saw idles but the chain doesn’t move. The 800 manual adds that the clutch should engage between 2800 to 3000 rpms.

Both manuals specify 32/1 using MAC 40/1 oil. 850 adds: “NOTE: Because the PM 850 has a very high performance engine, the normal fuel-oil ratio of 40:1 should be decreased slightly to 32:1 when using McCulloch Custom Lubricants. If McCulloch oil is not available, use a good grade of SAE 40 two-cycle oil mixed 20:1.”

Ron

 

[PogoInTheWoods]

With no chain, Brian and I were between 12,300 and 12,900 on our 800s and 12,500 on a PM850. Brian later melted the piston on the 12,900 saw. I don’t have a tach so I don’t know how much to deduct for a spinning chain.

Not sure what the difference in rpm would be but the air/fuel mixture would obviously remain the same with or without a chain as it also would in a cut. I think it's fairly safe to say that 12K+ is entering a fairly iffy range for these saws even at a 32:1 mix ratio. I'd also respectfully suggest that they probably make more power a little richer anyway and 11.5 may be a more appropriate target when using a tach. My 800 starts to lose its 4 stroking right around 12K. Haven't pushed my PM8200 and don't intend to due to the unobtanium pistons and what I went through to revive the scuffed one I already have!

Interesting that the info on the sheet for the PM8200 suggests 2800rpm for idle and 3400 for clutch engagement when it uses the same clutch as the 800 and 850S. The PM850 has different (old) part numbers and does appear to have smaller springs in the illustrations in the IPL I have. Could still be the same clutch with a different illustration and the old numbering system, I suppose.

 

[rwoods]

The 800 manual I have is for the early 800s - probably has the same clutch set up as the 850. Ron

 

[2broke2ride]

I pulled the carb apart on the 7-10 tonight. This time I went ahead and removed the welch plugs. Found a decent amount of crap in the high speed check valve as well as a fleck of yellow paint in the idle circuit, presumably from the fuel tank. Not sure how it would have made it past the fuel filter and the screen in the carb to end up there. Installed new welch plugs and the carb is currently sitting overnight for the sealer to dry.
I also noticed that I think I had the metering lever a smidge too low so I will tweak that a bit too. Hopefully this gets this saw screaming like I know it should.

 

[Scott Sonntag]

I ended up finding the spring on the floor of the shop, it must have come out when I pulled the brass insert out of the fuel cap. So I placed the spring back in the cap and I actually had an old poulan chainsaw sitting nearby. Took off it's fuel cap and there was the green duck bill valve I was needing. I installed it on top of the spring and then pressed the insert over it, back into the cap. Turned the 10-10 on it's side and almost no fuel leaked out. A small amount did come out and from what I can tell is it's coming from the cork gasket. Maybe I just need to give the gasket time to swell. The mating service on the tank is smooth and even. As anyone tried any other kind of gasket types for the fuel cap?

Scott

 

[fossil]

"O" rings work well.

 

[heimannm]

There is a thread with photos from Baraboo in the chainsaw section, Kris (nogoinback) started it.

Mark

 

[2broke2ride]

I pulled the carb apart on the 7-10 tonight. This time I went ahead and removed the welch plugs. Found a decent amount of crap in the high speed check valve as well as a fleck of yellow paint in the idle circuit, presumably from the fuel tank. Not sure how it would have made it past the fuel filter and the screen in the carb to end up there. Installed new welch plugs and the carb is currently sitting overnight for the sealer to dry.
I also noticed that I think I had the metering lever a smidge too low so I will tweak that a bit too. Hopefully this gets this saw screaming like I know it should.

Ok guys, this is really throwing me for a loop. Put the carb back together and back in the saw and same result. Swapped the carb from one of my good running 10-10s and same results so that eliminates the carb in my eyes.
To recap. The saw is rebuilt, NOS piston and rings, gaskets, seals. OEM kit in the carb. I have yet to get it to run "right" in order to get it to idle, I have to lean out the low so much that it bogs severely on acceleration, if I richen it enough to get rid of the bog, I cant turn in the idle screw enough to keep it idling. If I split the difference I can kind of get it to stay idling with a little throttle blip every now and then. Turn to the high needle. It seems to respond as I would expect. If I get it sort of right, and then make a couple of cuts with it, it goes lean with a racing idle etc. It is strange because on one hand, it acts like it doesnt want fuel, and on the other it acts lean. Also worth mentioning, might be, the exhaust fumes are so noxious they make your eyes water, I dont remember that from any other saws or sleds I've worked on and ive worked on a lot.
The only thing I havent really checked, because I lack a good way to do it, is the fuel line. I'm wondering if it has a pinhole or something. I also need to get a better setup for pressure testing. The setup I have I made years ago for checking sled engines, it runs on compressed air and is not really fine enough for saws.

Sorry for the long winded post, just hoping someone might have ideas for me.