Thoughts on cheap McCulloch 250?

[Coralillo Lo Pro]

Guy on CL locally has a regular yellow 250 says starts right up, only wants $50 for it. I'm not a collector and not sure what I really need it for if I get my rebuilt Stihl 045 and 056 Supers finally fixed up right once and for all, but seems kinda hard to argue with a bombproof 80cc classic like that for the price.

 

[Mad3400]

As a Certified Enabler, that's a great deal and you should add it to the arsenal...

Mad3400

 

[heimannm]

Just recognize that the 250 is manual oiler only so be prepared to pump continuously while using that saw. 80cc's and a lot of torque but not really a high RPM model.

Mark

 

[Coralillo Lo Pro]

Just recognize that the 250 is manual oiler only so be prepared to pump continuously while using that saw. 80cc's and a lot of torque but not really a high RPM model.

Mark

Good to know hadn’t paid attention to that aspect. Kind of an impulse buy not sure how much I’ll use it. Might rig it for lo pro milling w an auxiliary oiler if it runs well enough. Run an 8 tooth LP sprocket. Might just flip to a collector. We’ll see how it runs.

 

[Coralillo Lo Pro]

Okay, amid a sea of orange and red there is now yellow. Started right up almost first pull, Tillotson HL carb, seems in great condition. He threw in a bunch of oil as well. It’s a tank. Hell of a saw for $50. Hadn't looked at the max rpm spec til now - on the Collectors Corner site say 6000rpm is max. Ah, read some old posts on this saw - that 6000rpm number is probably the rpm for max hp under load. The Stihl 880 is max power at 8500 rpm. Something higher revs like the Husky 592XP is max power at 9600. If that's the case it's geared way more toward the low end than an 880 even. But as numbers are thrown unreliably around the internet endlessly for specs, for all I know that number is the rpm for max torque, which would be in line with an 880 or 3120. Would be interested if anyone has put a tach on their 250 to get real world numbers.

 

[Coralillo Lo Pro]

More fun facts - apparently they didn't have 2 cycle oil back then so it recommended 16:1 of SAE40 or 20:1 of McCulloch Oil, whatever that was. I understand from other posts that 40:1 or 32:1 of modern 2 cycle oil they run just fine on. And didn't people roast their hands running these things, with the cylinder in back and gas tank in front? Don't know how it started and revved when he tested it for me, couldn't get it to keep running at home. Gas stunk like ancient rotten fuel, thought maybe that had something to do with mixing 40 weight in it, but no, it looked like gas hadn't been changed in 40 years lol when I poured the old stuff out. Tank to carb hose was leaking, put a clamp on the fitting, put good new two cycle fuel in, cranked right up and ran great. Will need a bit of tuning and a fresh chain grind.

 

[Coralillo Lo Pro]

Well, ran great is an exaggeration. Ran and revved decent, but seemed slow and gutless trying to cut. Thought it might just be tuning, but had been too easy to pull for an 80cc saw so ran a compression check and only 75 psi or so. Will have to have a look at the piston and cylinder to see what state they're in. Manual oiler doesn't seem to work either. So, probably about right for $50 lol. Interesting little thing I learned about the .404 chain and bar on it. I believe it's the old original .404 chain with an .050 bar, so because it's a roller nose I can put a 3/8LP ,050 chain on and the only thing I have to do to run lo pro on it is put an LP drive sprocket on it. But now it will have to get in line behind doing the latest fixes on my Stihl 87cc rebuilds.

 

[buzz sawyer]

Using that much oil, could have stuck rings.

 

[Coralillo Lo Pro]

Using that much oil, could have stuck rings.

Was my thought - the Stihl 045 Super I'm troubleshooting that I rebuilt ran good for a bit after rebuild but kept dying and finally wouldn't start at all. Turned out to have only 60 psi at that point, and thought it was the cylinder gasket at first but turned out to have stuck rings. Just replaced them and put the head back together. The Mac uses the same rings as it. Will go ahead and get another set of those 54mm Cabers if that turns out to be all that's wrong.

 

[Okie]

Them Old 250 Mac's will not start easy with only 75 psi and you say your other saw only checks 60. I've seen several that do not want to start easy especially when cold coming out of storage and nothing wrong with them, just prime them through the cast muffler (like is on yours) and hold the throttle wide open for a cold start. You are lucky that yours starts easy when cold which makes me think that it's problem is not low compression.
I would think about getting a 2nd opinion from a know correct reading SMALL ENGINE compression gauge. It really can be misleading when a gauge lies to you about correct compression.
(I've seen more than one instance where guys would do a complete re-build on a chainsaw due to BLAMING low compression and their AUTOMOTIVE COMPRESSION gauge would read less after their overhaul and the saw still not run due to other issues)
They usually say, I know my gauge is accurate because it cost me big bucks from Snap On and it reads ok when I test it on my 80 gallon tank air compressor and on auto engines.

Them OLD 1-43, 1-53 and 250 series of Mac saws cut good with the bog toothy 404 chain when all is correct.
Also you say it sounds slow and gutless. They do not rev up and scream like a Stihl, that is why they use the bit tooth chain. Lots of torque.
I have some of them old big heavy Mac's and I use them mainly after a big log is down on the ground, just set the saw on top of the log and it's weight does the cutting, can hold it with one hand and drink a cup of coffee while it's doing it's thing. (Do not forget to operate the oiler after running a auto oil saw.
I like the sound of them old Mac's when they are in the wood. I run 40:1 mix with no issues.

Mark Heimannm knows them old Mac's inside and out.

I've got a really low hour 1-43 and OEM owners manual and parts lists..

 

[Coralillo Lo Pro]

Them Old 250 Mac's will not start easy with only 75 psi and you say your other saw only checks 60. I've seen several that do not want to start easy especially when cold coming out of storage and nothing wrong with them, just prime them through the cast muffler (like is on yours) and hold the throttle wide open for a cold start. You are lucky that yours starts easy when cold which makes me think that it's problem is not low compression.
I would think about getting a 2nd opinion from a know correct reading SMALL ENGINE compression gauge. It really can be misleading when a gauge lies to you about correct compression.
(I've seen more than one instance where guys would do a complete re-build on a chainsaw due to BLAMING low compression and their gauge would read less after their overhaul and the saw still not run due to other issues)

I'm going by feel too - it's a ridiculously easy pull for an 80cc saw. I will admit I don't trust my new-ish Bosch gauge though it's supposed to be good quality - may not be getting a good enough seal with it. Feel like it may often read between 10-25 psi low going by other readings. My good compression 056 Super takes the expected effort to pull where my bad compression 045 Super was at least as easy as the Mac. I should take test readings on all the saws I have to compare. Anyway, I know the Mac is a low rpm saw and I don't expect much speed and I should work on some tuning yet, but I'm fairly certain the compression isn't close to what it should be. Need to peer into cylinder and see what it looks like, and go from there. But first have to finish getting the Stihls back together and running right. Just tested the Stihl with new rings and still a pristine new-ish cylinder and piston (and no gasket now, just thin grey high temp RTV) and it's only 130 psi on the gauge when I suspect it's at least 150 if not 160 or more, so yeah, this tester leaves a lot to be desired. It just doesn't tighten well. The other good compression Stihl only reads 120 when I suspect it's more like 150.
People seem to have problems with extension tubes on testers which is what my Bosch 7527 came with, there's no way to use it without one. The 7528 kit looks better, it has both a flexible and solid extension. Have read comments where people have gotten as much as 40 psi lower reading using the extensions. Some folks say they just take more time to fill up and should read the same, but doesn't always seem to work out that way. I guess a lot of folks use them to compare compression between cylinders and think it doesn't matter the readings as long as they're consistent, but for a single cylinder you want to know the real compression, it matters.

 

[Coralillo Lo Pro]

Didn't realize how completely unreliable most compression testers are for chainsaws and other small engines, even the ones with schrader valves which supposedly work with small engines. Must be a ton of people being misled by wildly off readings.

 

[Okie]

That is one reason I have two small engine compression testers that I know are accurate and I only use them on small cc engines.
If I get a bad test with one, I get a second opinion from my other one.
I've seen some good auto mechanic's that feel awful weak upstairs AFTER they found out their compression tester lied to them. Most of the mechanics had the SHOW ME ATTITUIDE, but were not from the show me state of Missouri.

 

[Coralillo Lo Pro]

That is one reason I have two small engine compression testers that I know are accurate and I only use them on small cc engines.
If I get a bad test with one, I get a second opinion from my other one.

Have seen both the Stens and the Echo recommended. Have concluded my inexpensive Bosch is useless for small engines. Good chance the Mac 250 has 125 psi. The Stihl 045 Super has huge compression now w the new Caber rings and finally runs like it should w the new ignition.

 

[Coralillo Lo Pro]

Got a new clutch drum off Ebay that said it fit the 250 so I could put any rim sprocket I wanted to on it. I paid no attention to it saying the drum was for a 9/16 shaft assuming they were all the same. Then made the discovery a few other ancient Mac owners have made that some of the earlier large frame saws have 5/8" shafts and don't use a needle bearing, but a bushing instead. So the rim sprocket clutch drum is no use for my saw, and had to order an Oregon 10608 clutch drum for the saw, a bit more of a rarity.

 

[heimannm]

On some of those drums it is possible to push the bushing out and press a bearing with the 9/16" I.D. in. I'd have to consult my spreadsheet to remember which drum(s) will work that way.

Mark

 

[Coralillo Lo Pro]

On some of those drums it is possible to push the bushing out and press a bearing with the 9/16" I.D. in. I'd have to consult my spreadsheet to remember which drum(s) will work that way.

Mark

That may be the case but I need the ID of the bearing to be 5/8" not 9/16". I read what you posted on ope about this -

"103688 is the same as several other McCulloch part numbers including 68866, 87111, and 90360 which are an SCE910 or just 910 bearing with an O.D. of .750".
As far as I know, the only large spline drum that will fit the 5/8" crankshaft for the large frame saws is an Oregon 10608 and is fit with a bronze bushing.
I have bearings (9/16x3/4) and bushings (5/8x3/4) that can be used in the large frame drums like 90359 but at this moment I am not aware of any spline drums with bearings that will fit the large frame saws using the 5/8" crankshaft.
I do have a few 60919 drums with bearings that fit the 5/8" crankshaft but they have a fixed rim .404-7 sprocket, not the splined/floating rim type that allows you to replace the sprocket independently."

I pressed out the bronze bushing on the OEM 5/8" spur sprocket drum to discover of course it did not fit inside the 90359 drum I bought. I ordered a used 10608 off Ebay with a decent clutch too for reasonably cheap, which as you say above, is the only thing you know of to fit those 5/8 crankshafts.

 

[Coralillo Lo Pro]

Another useful discovery now I've learned not to assume anything about this saw - not an OEM bar I don't think, no markings on it but seems to be .063 not the original odd McCulloch .404 .050 chain. Knowing that now and that the manual oiler isn't working, not sure I should have bothered throwing good money after bad at rim sprocket setups to allow different chain pitches. The .404 spur was fine. Likely should have just gotten a new .404 chain, tuned it some, and called it a day.

 

[Coralillo Lo Pro]

Back to original suspicion it needs new rings. Starts up in morning when cool and runs okay for a bit. Trying to start up after that results in endless small sputters but won't stay running. Fuel line and filter in tank were in horrible shape, replaced them, no difference. Carb probably needs a good cleaning, but feel like it may be right on that edge of compression where it will start when cool but not enough compression anymore when warm.

 

[Coralillo Lo Pro]

On some of those drums it is possible to push the bushing out and press a bearing with the 9/16" I.D. in. I'd have to consult my spreadsheet to remember which drum(s) will work that way.

Mark

After last time I ran it for a few minutes it will only cough/sputter and not restart. Thought it was maybe low compression, wouldn't start when warm, but same when cold too. Ultrasonic cleaned the carb, tried again with no luck with the the cleaned carb. Diaphragm is intact but stiff and ancient, so ordered a carb kit. Just seems to not be getting enough fuel, plug is never soaked. So still seems to be in the HL carb, guessing the diaphragm is likely, though surprised it worked at all before. More time I spend trying to start it and wearing my arm out, more I'm thinking the compression is okay. Will know about that when I get my new tester. So far everything has been what you'd expect in an ancient saw that's been sitting forever, as far as replacing fuel lines/filters and carb work.