McCulloch Chain Saws

[Brian13]

Thanks for all the advice, guys. I am starting to lean towards a 250 now. I am looking at a few runners in good condition. I'd love me a Super Pro, but they aren't showing up yet. I'll keep looking. These saws look like a lot of work to mod compared to modern saws. That's a lot of ports in there...

The 7-10 is more comparable to a modern saw porting wise. Jacob just posted some info for porting the older style Macs. I barely understand how porting works on new saws, the loop scavenging system has me lost. Look at post 135 its all in order, http://www.arboristsite.com/chainsaw/184946-9.htm.

 

[sachsmo]

Anyone got any tricks before i go to far.

Aerokroil, any good penetrant, let sit for a day, then try tightening before loosening.

Old Macs are Mag/Aluminum heat always works too.

 

[briantutt]

Anyone got any tricks before i go to far.

Someone on here recommended a 50-50 mixture of ATF and acetone. It worked on my dads old 9N Ford tractor carb when nothing else worked.

 

[wudpirat]

Got me another yellow saw

Ronnie, my son's dirtbike riding buddy, showed up the other day and said " Hey Pops, I got a yellow chainsaw in the car for you, I know you have a bunch of yellow saws , thought you could use another." Huh? Is the pigs ass pork? A yellow chainsaw, you betcha.
So he drags out this weird looking yellow saw, I ask, What it is? Says MAC 15 on the gas tank, want it? Here, he hands me this filty hunk of metal.
It's MAC 15, says so on the decal on tank, Mac loglo on the starter cover, a 20" bar that has all the rust you can get on a bar and the nastiest big toothed chain.
A couple pulls on the recoil showed it wasn't frozen and had compression. Starting to look promising.
A couple wipes with a rag and I'm seeing bright yellow. The saw was covered in black oily sawdust, eccept for the bar and chain, There was even paint in the screw slots, never taken apart. A liberal dose of KROIL got the chain free and moving on the bar but only part way. Same thing with the chain moving the other way, something was locking up. Then came the loud clicking noise and the recoil locked up.
I removed the muffler( exhaust stack) no screen or baffles, twisting off one screw and looked at the piston.
The piston was discolored but scuff free and the rings were free, looked great.
Now to find out what locked up the crank.
Checking Mike Acres' site, I have a MAC 15, 1962-1969, 80cc, 19 lb plus bar early MAC consumers saw. Altho I can't see a 80cc saw listed as a consumer's saw, it's 1cc biger than my Dolly 7900.

Guess I'll try to get it running and see how it stacks up againt my MAC 10's and put it on the shelf with my ten other saws.
There is a couple of spots (white death) on the fan shroud, some black paint missing on the gas/oil tank. I think the oily sawdust protected the finish durring storage, three years in a dog houise after beng saved from the recycle bin at the town dump.
If the fuel is gravity feed, how do you run the saw sideways? Never saw a carb that looked like what I got, looks like a lawnmower carb without the float bowl and a big cartridge filter monted up front.
Running or not, that saw with a bolt on fuel/oil tank and a 20" beaver tail bar will make a great coversation piece.

FREDM, The old wood pirate

 

[a. palmer jr.]

Mac 3-10

I just received a Mac 3-10DSP chainsaw and was wondering what the DSP means. This saw came out with a compression release (although I always forget to use it), figured it had something to do with that.

 

[wyk]

The 7-10 is more comparable to a modern saw porting wise. Jacob just posted some info for porting the older style Macs. I barely understand how porting works on new saws, the loop scavenging system has me lost. Look at post 135 its all in order, http://www.arboristsite.com/chainsaw/184946-9.htm.

I'm chatting up a couple folks that do kart motors for actual racing. Just picking their brains. I don't want a race saw. I just want to 'wake it up'.

 

[rwoods]

I just received a Mac 3-10DSP chainsaw and was wondering what the DSP means. This saw came out with a compression release (although I always forget to use it), figured it had something to do with that.

I believe DSP is MAC speak - Decompression Starting Port. Ron

 

[a. palmer jr.]

I believe DSP is MAC speak - Decompression Starting Port. Ron

Wow! That is a foreign language. Thanks Ron

 

[heimannm]

DSP = De Stroking Port, reduce compression for easier starting.

wyk - the 250 is an 80 cc saw, but you would find a 7-10 a lot more useful saw, the SP60 would be better for all day cuttng as well in my opinion. I ran my SP60, SP70, SP81, and PM800 today along with my SP105 and the new Dolmar 7900. I think the Dolmar and the SP81 were the most fun, but the SP105 made short work of the big maple trunks.

Mark

 

[heimannm]

whatscooking - if you don't have a strike impact you should consider getting one, the kind to twist and hit with a hammer. They really work wonders on both slotted and hex head screws.

Mark

 

[a. palmer jr.]

whatscooking - if you don't have a strike impact you should consider getting one, the kind to twist and hit with a hammer. They really work wonders on both slotted and hex head screws.

Mark

Not a good idea to buy a cheap one. I had one of those cheapies and it lasted just a few strikes and it was finished. They are good for removing stuck bolts and screws and making sure they are tight. We used to use them repairing dirt bikes.

 

[a. palmer jr.]

I wonder why an engine with low compression wouldn't be the same as far as starting as an engine with a compression release...

 

[heimannm]

What is happening below the piston is not affected by the DSP or compression release so you get a nice charge of fuel and air into the combustion chamber with good rings/piston. If the cylinder/piston/rings are shot, you may not get a good charge and thus no start. Older reed valve engines are less sensitive as the compression goes down but still get to a point where they simply won't run.

A lot of the old McCulloch documents say compression is not so critical, and a figure of 90 PSI is often noted as being adequate.

Mark

 

[wyk]

wyk - the 250 is an 80 cc saw, but you would find a 7-10 a lot more useful saw, the SP60 would be better for all day cuttng as well in my opinion. I ran my SP60, SP70, SP81, and PM800 today along with my SP105 and the new Dolmar 7900. I think the Dolmar and the SP81 were the most fun, but the SP105 made short work of the big maple trunks.

Mark

I got work saws. Now I want a play saw. It's utility will merely be a side effect. I want a 250 for it's good looks and the sound of it.

 

[RandyMac]

The old 250 has infected more people with Yellow Fever than the 10-10s.

This 250 is my testbed for carbs, it has the most compression of any 250s I have had.
It normally has a choke equipped Flatback in it. It is also a mix of parts, to my own specs.

 

[CM76]

DSP = De Stroking Port, reduce compression for easier starting.

Mark

It is interesting that the DSP question has come up. I have seen McCulloch advertise the DSP acronym as the 'De Stroking Port' as well as 'Decreased Starting Pull' as can be seen in the attached brochure below.

Looks like you had a good day with the saws Mark - great photo of the pride.

Regards,

Chris.

 

[psuiewalsh]

The old 250 has infected more people with Yellow Fever than the 10-10s.

This 250 is my testbed for carbs, it has the most compression of any 250s I have had.
It normally has a choke equipped Flatback in it. It is also a mix of parts, to my own specs.

Never thought of priming a saw with Jim Beam before. No wonder it has so much compression.

 

[Warped5]

Never thought of priming a saw with Jim Beam before. No wonder it has so much compression.

His methods may be unconventional, but you cannot argue with the results.

Love that photo, Randy!

 

[a. palmer jr.]

What is happening below the piston is not affected by the DSP or compression release so you get a nice charge of fuel and air into the combustion chamber with good rings/piston. If the cylinder/piston/rings are shot, you may not get a good charge and thus no start. Older reed valve engines are less sensitive as the compression goes down but still get to a point where they simply won't run.

A lot of the old McCulloch documents say compression is not so critical, and a figure of 90 PSI is often noted as being adequate.

Mark

I hadn't considered that part below the piston. Guess my brain went to sleep or something.. Thanks Mark

 

[whatscooking]

Just got to say it, i love the two finger starting :tongue2: