MCCULLOCH The official McCulloch thread

[Al Smith]

Be advised if you don't already know or for that matter if anybody doesn't know .The 82 cc macs had three different sizes of pistons .If you are going to change out a piston make certain you get the correct one .

 

[Sleeper]

And don't bother with porting it. You won't see much of a gain. I did that once and it just didn't seem to do much.

Shaving a tiny bit off of the flywheel key for a tiny bit of advance will help a little. Take about .010-.015" off of the key and make sure you put it in properly (advance, not retard)

Only if you want. These run good as they are. Mac knew what they were doing... good reason they were around for so long.

But like Al said, watch the piston size... they had "A", "B", and "C" pistons. Different part numbers for the pistons. I recall that the top fin of the cylinder also has either "A", "B" (or nothing), or "C" stamped on it. "B" is the most common... if the top fin of the cylinder is blank, you can be fairly sure it's a "B" cylinder.

 

[TJ the Chainsaw Mechanic]

And don't bother with porting it. You won't see much of a gain. I did that once and it just didn't seem to do much.

Shaving a tiny bit off of the flywheel key for a tiny bit of advance will help a little. Take about .010-.015" off of the key and make sure you put it in properly (advance, not retard)

Only if you want. These run good as they are. Mac knew what they were doing... good reason they were around for so long.

But like Al said, watch the piston size... they had "A", "B", and "C" pistons. Different part numbers for the pistons. I recall that the top fin of the cylinder also has either "A", "B" (or nothing), or "C" stamped on it. "B" is the most common... if the top fin of the cylinder is blank, you can be fairly sure it's a "B" cylinder.

Great stuff to know!

 

[Al Smith]

I've got the service manual on micro fiche .If I'm correct it mentions something about using an "A" piston on a "B" cylinder and a B in a c cylinder .I always assumed because of the time period and the machining and plating methods of the time they could not keep the cylinders within specs therefore requiring different piston which are easier to machine .Fact be known neither could the automotive companies before about 10-12 years ago .
As mentioned it seems the b size pistons are relatively easy to find,a pistons are somewhat more rare as are c's .Somebody on flea bay has generic pistons but how well they might work I have no idea .

 

[Steve]

You have to use the corresponding piston in the correct cylinder. A IN A, B IN B, and C IN C. The differences are just a few thousands of an inch.

Mcculloch had the right idea early on. You can make up for machine variation between cylinders quicker and cheaper if you're not paying a guy check to make sure all the cylinders are exactly 2.062"

 

[Al Smith]

In case nobody knows as of a few years ago Honda Accords were also assembled by a select fit process .They make a pretty good engine .Modern day Fords are all bored out to a number 2 bore size which does not vary by over a few microns .Todays CNC machines don't miss on size .
Give me a few days to find the article in the micro fiche on the 82 cc engines regarding miss match bore/piston and what the tolerance variations are .
I would agree it would be best to match bore sizes but I think in a pinch a little bit of slop might be acceptable .

 

[Al Smith]

--More--- Machining aluminum is much different than iron or steel ,.Ambient temperature plays a bit role on the finished product .For example the parts are all cut using coolant which should be real close to 70 degrees F or the size will be all over the place .They were not all that aware of that when the saws were made .

 

[Al Smith]

I couldn't find the bore/piston mismatch comment .This is what I did find.As per factory specs it should be 3 to 5 thou skirt to cylinder with 5 thou or less ovality and taper in the cylinder .
I doubt in all honesty if very many would be within tollerance these days but never the less seem to run just fine .
In looking at the cylinder bore for the most part it's about .0009 between a to b b to c.less than a thou .Then within bore range you have .0007-.0008 a b or c .So I suppose considering wear etc if you had a fitment of 3 to 5 thou or so it might be good to go .A little sloppy probably would not hurt ,tight might not be good< well depends on what we are talking about without further ado .

 

[PogoInTheWoods]

FWIW, this is out there for consumption and reference and was included in a batch of files I received from another member some time ago.

 

[Al Smith]

That's the same one I have on micro fiche of which I have no means to copy .Good info .
I might have mismatched the bore to piston when I replaced the 805 cylinder which had peeled the chrome with an older style 850 cylinder .I didn't measure it .I cooked the freakin thing by straight gassing it with a prime,that really sucked .So,on the list it's cleaning the cylinder and trying to determine bore size but one thing is for certain,I'll not pony up 90 bucks for an "A" bore piston .I like my Macs but not that much .

 

[TJ the Chainsaw Mechanic]

That's the same one I have on micro fiche of which I have no means to copy .Good info .
I might have mismatched the bore to piston when I replaced the 805 cylinder which had peeled the chrome with an older style 850 cylinder .I didn't measure it .I cooked the freakin thing by straight gassing it with a prime,that really sucked .So,on the list it's cleaning the cylinder and trying to determine bore size but one thing is for certain,I'll not pony up 90 bucks for an "A" bore piston .I like my Macs but not that much .

Hey Al,
where are the letters stamped for the piston sizes? So far all I found was a B on the crankshaft. EDIT: DRRR! Nevermind...it was mentioned above lol Thanks

 

[ajschainsaws]

another 10-10s best condition yet
@hseII thanks for the bar

 

[ajschainsaws]

 

[PogoInTheWoods]

Remarkably nice!

 

[TJ the Chainsaw Mechanic]

Jealous.....hope when I paint my 850 it looks that nice lol

 

[Lee H]

Andrew, I have the same exact 10-10s and mine is pristine.
I don't think it was used but maybe a couple times. Thought
I had some pic's but can't find them.

 

[ajschainsaws]

Thanks everyone this one is a strong runner they do vary some of these 10-10 I've had a right starter automaric here that was as strong as a straight promac 10-10

Looking into the 800 series now haven't got any around

 

[astnmacgto]

Thanks everyone this one is a strong runner they do vary some of these 10-10 I've had a right starter automaric here that was as strong as a straight promac 10-10

Looking into the 800 series now haven't got any around

The 82cc series rock, @heimannm has pretty much all of them. I've only got a pm800 pm850 and a pm8200

 

[ajschainsaws]

The 82cc series rock, @heimannm has pretty much all of them. I've only got a pm800 pm850 and a pm8200

That's the numbers I like Maybe the 81 as well you got a good arsenal there

 

[ajschainsaws]

Andrew, I have the same exact 10-10s and mine is pristine.
I don't think it was used but maybe a couple times. Thought
I had some pic's but can't find them.

Just for you Lee I would take any of your saws and do a free photography service
Return shipping could be a bit tricky