McCulloch super 250 for $60 Deal or No Deal

[August76]

Here's some pics. Looks like they rebuilt it by looking at the gaskets hanging out

 

[heimannm]

A lot of folk don't like the Mac carburetors because they are different and the gasket and diaphragms are more expensive. I think a properly working Mac carburetor offers more oomph.

Mark

 

[Okie]

A lot of folk don't like the Mac carburetors because they are different and the gasket and diaphragms are more expensive. I think a properly working Mac carburetor offers more oomph.

Mark

Here is a link to a thread on this site about a guy with a 1-51 asking questions and carbs that will fit onto your saw plus other info.

https://www.arboristsite.com/commun...-that-aint-run-in-awhile.319907/#post-6541296
I've converted some Mac's from the Mac carb to the Tillotson's. (mainly because I could find a Tillotson carb kit for around $15 and had other parts saws that had a Tillotson carb as a donor vs trying to find kits and parts for the Mac carb's) Have to keep a heads up about the chokes and linkages as to which type Tillotson to use and which side of the handle the oiler.choke is located. (the choke and oiler location varied Left and Right at the air box by the handle), therefore different carb linkages. The Mac carb's were actually made by Mac and they later went to the Tillotson carbs.

Chainsawyr.com sometimes has the conversion kits or sometimes you can see the pictures of the linkages and review the Mac stuff, etc.

I've bought couple of Tillotson carbs off of ebay dirt cheap at times, and you will see mentioned Kart Mac saws parts. Go Kart racers liked the old bullet proof Mac power heads.

Several parts from the 1-40 thru the 1-50 series of Mac's will fit your 250.

"heimannm helped me with lots of good info when I first started flogging the Mac's sometime ago.
Their is also McCulloch chainsaw info at this link.
It's from the stickies section at the top of the chainsaw forum page.

https://www.arboristsite.com/community/forums/chainsaw-stickies.127/

 

[a. palmer jr.]

I'm not too experienced with the 250s but it sounded a bit lean to me. I would give it a vacuum/pressure test if it was mine, just to be sure it doesn't leak...Could just be the carb though..

 

[Okie]

I'm not too experienced with the 250s but it sounded a bit lean to me. I would give it a vacuum/pressure test if it was mine, just to be sure it doesn't leak...Could just be the carb though..

I did not hear any 4 cycling either. Might just be carb adjust. Also I run anywhere from 32:1 to 50:1 mix instead of the old school 16:1 area. If mosquitos are bad use the 32:1 for more smoke.

You need to make sure it's 4 cycling and not running lean BEFORE doing any more heavy load cutting.

Also I've seen some of those old Macs that idle would change or get erratic as the chain tension is changed from loose to tight.
Take the chain off or loosen the chain and the idle would change, usually idle more consistent with no chain.
this is a indicator that the clutch side crank seal is dry and leaking. (the Bearing would still be ok) A crankcase pressure test would reveal such.

This crank seal can be wormed pulled/pried out with gentle care. I think I drilled a itty bitty hole in the steel rim and used a thin sharp awl or each side of the seal to get it started then a small sheet metal screw that I could pull/pry on.

Sounds like you have a good runner, don't melt it down by running it too lean.

 

[August76]

I did not hear any 4 cycling either. Might just be carb adjust. Also I run anywhere from 32:1 to 50:1 mix instead of the old school 16:1 area. If mosquitos are bad use the 32:1 for more smoke.

You need to make sure it's 4 cycling and not running lean BEFORE doing any more heavy load cutting.

Also I've seen some of those old Macs that idle would change or get erratic as the chain tension is changed from loose to tight.
Take the chain off or loosen the chain and the idle would change, usually idle more consistent with no chain.
this is a indicator that the clutch side crank seal is dry and leaking. (the Bearing would still be ok) A crankcase pressure test would reveal such.

This crank seal can be wormed pulled/pried out with gentle care. I think I drilled a itty bitty hole in the steel rim and used a thin sharp awl or each side of the seal to get it started then a small sheet metal screw that I could pull/pry on.

Sounds like you have a good runner, don't melt it down by running it too lean.

When I said 4-cycle I just meant it kind of felt like I was cutting with the lawn mower engine sort of that slow and steady compared to a 2 stroke it runs like a tank

 

[heimannm]

The Mac family of carburetors were manufactured by Walbro.



Mark

 

[August76]

The Mac family of carburetors were manufactured by Walbro.

View attachment 667910

Mark

Nice mines the walbro Mac. So it's not made by Mac hmmm.

 

[August76]

Took the bar off and I'm cleaning up all the dirt and grime with that orange cleaner and Air blowgun
What would be the closest yellow paint to restore some of the bad spots.
Picture right before it dumped.i got wood to cut
Damn monsoon storms keep hitting us here

 

[August76]

Found a lil jb weld on the side cover
Here's a video of it after I adjusted the carb yesterday. It's still holding back

 

[a. palmer jr.]

That's more like it, I think I heard a little 4 stroking going on when it was revved up...

 

[August76]

That's more like it, I think I heard a little 4 stroking going on when it was revved up...

What exactly is it when you say 4 stroking. Like it skips a stroke ?

 

[Okie]

What exactly is it when you say 4 stroking. Like it skips a stroke ?

You can see several videos (and threads) of such if you will search, How to adjust a chainsaw carb for four stroking.

Briefly it's backing out (counter clock wise) the H jet from smooth sound to what sounds like a slight miss at High throttle (running rich on gas) and when the saw is placed in the wood under load it will sound like it's missing (4 stroking) then smooth out under load and 4 stroke when you lift it out of the cut or the load decreases.

Rich is rich on gas which keeps the piston cooler, lean is too much air not enough gas which causes the temp of the piston to increase, sometimes very rapidly under heavy load in a long cut and piston/cylinder scoring.

4 stroking is normally readily apparent sound on your old Mac. Once you get familiar to the sound you will listen for such when using a chainsaw, especially if it's your own chainsaw.

I use them old heavy Mac's quite often after I get a big log down, (I use a lighter weight saw for felling) just let the weight of the saw do the cutting.

Several Model of side covers will fit your 250, I think the 1-40, 1-50 series plus some others. You might just keep a eye and ear open for a reasonably priced replacement. (finding a good one priced right will be the trick)

A donor saw for spare parts is a good thing to have around if you are going to use the old Mac quite a bit. I have some Mac's for spare parts that were dirt cheap from garage sales and junk piles. (just keep an eye and ear open)

 

[August76]

You can see several videos (and threads) of such if you will search, How to adjust a chainsaw carb for four stroking.

Briefly it's backing out (counter clock wise) the H jet from smooth sound to what sounds like a slight miss at High throttle (running rich on gas) and when the saw is placed in the wood under load it will sound like it's missing (4 stroking) then smooth out under load and 4 stroke when you lift it out of the cut or the load decreases.

Rich is rich on gas which keeps the piston cooler, lean is too much air not enough gas which causes the temp of the piston to increase, sometimes very rapidly under heavy load in a long cut and piston/cylinder scoring.

4 stroking is normally readily apparent sound on your old Mac. Once you get familiar to the sound you will listen for such when using a chainsaw, especially if it's your own chainsaw.

I use them old heavy Mac's quite often after I get a big log down, (I use a lighter weight saw for felling) just let the weight of the saw do the cutting.

Several Model of side covers will fit your 250, I think the 1-40, 1-50 series plus some others. You might just keep a eye and ear open for a reasonably priced replacement. (finding a good one priced right will be the trick)

A donor saw for spare parts is a good thing to have around if you are going to use the old Mac quite a bit. I have some Mac's for spare parts that were dirt cheap from garage sales and junk piles. (just keep an eye and ear open)

Thanks for the info. So it's normal to sound 4 stroke not under load but it will smooth out in the cut?

 

[heimannm]

If it is adjusted correctly, it will 4 stroke (sounds rough) when it is unloaded, and clean up (sounds smooth) in the cut, yes.

Mark

 

[August76]

If it is adjusted correctly, it will 4 stroke (sounds rough) when it is unloaded, and clean up (sounds smooth) in the cut, yes.

Mark

ok. So it should sound ruff

 

[SEAM]

This is one of my Mac 795s. If you listen closely the engine sort of gargles a bit prior to each cut and then clears up in the cut... the chain is not very sharp, though

 

[August76]

This is one of my Mac 795s. If you listen closely the engine sort of gargles a bit prior to each cut and then clears up in the cut... the chain is not very sharp, though

Speaking of chains. And bars. This chain is a Stihl marked 404 on the tooth and 6 on the drive link. Any ideas what that is. I looked on Google and it's unclear to me. Is this a 28 inch bar?

 

[2broke2ride]

I can tell you the chain is .404 pitch full chisel skip tooth.
That is a cool old roller nose bar, put a tape measure to it and subtract about 4 inches to get the useable length.

 

[August76]

I can tell you the chain is .404 pitch full chisel skip tooth.
That is a cool old roller nose bar, put a tape measure to it and subtract about 4 inches to get the useable length.

0k so .404 but what is the full chisel part? I knew it was a skip tooth. Bar measured a bit over 30 inches