McCulloch Chain Saws

[ric5141]

hi to all the mcculloch men hope you are all well, i have a small problem with our cp125 backfiring about every 30 seconds whilst cutting at full revs. we had a lot of issues with spark and earths on the saw when we first aquired it from the rubbish tip. after removing some dodgy looking home repairs the saw ran fine. now it has this backfire going on that thats loud enough to scare a pilot at 30,000 feet! any help or tips would be much appreciated
aaron

SOunds like timing points/condenser When I used to work on cars with points if the condenser was bad it would pop through the carb something awful

 

[a. palmer jr.]

I had an old Homelite that would short between the metal on the points and the mounting post. I fixed it by going to Mega-Fire solid state ignition. You might try new points and condenser and timing it with an ohmmeter.

 

[RandyMac]

250

The standard 250, everyone should have atleast one of these.

 

[leeha]

Hey Randy ole buddy,
Thought you said everyone should have a Super 250.
I bought a nice one, Just waiting for it to arrive.



Lee

 

[RandyMac]

Yep, I said that Lee, they also need a 103cc geardrive and 3-4 10-10s.

 

[sefh3]

I think everyone should have at least 2 of these bad boys. One just isn't enough.

 

[a. palmer jr.]

Yep, I said that Lee, they also need a 103cc geardrive and 3-4 10-10s.

I guess I'm part of the way there, I have 1 10-10 and a 700. I guess we're not counting Eager Beavers, Mini Macs, and 610s.

 

[RandyMac]

I set this one up for the boy, he was cutting 20" Alders. When he got to bigger trees, I lent him a Super 250, he didn't squeeze a trigger on a 250 again and still has the Super.

 

[leeha]

Yep, I said that Lee, they also need a 103cc geardrive and 3-4 10-10s.

I have the 103cc geardrives covered, But not 10-10's,
Although i just got a LG2 bow saw. Doe's that count.


Lee

 

[willysmn]

Mac 250

Please educate me on the difference between the 250 and the Super 250.
Thanks
Willysmn

 

[RandyMac]

I have the 103cc geardrives covered, But not 10-10's,
Although i just got a LG2 bow saw. Doe's that count.


Lee

Lee Buddy, that is a good start. I don't know how many models are in the -10 series, but they would keep a guy outta trouble while finding them all.

 

[heimannm]

The Super 250 has more aggressive porting, and a longer stroke (1.5" vs. 1.375") giving it a displacement of 87 cc vs. 80 cc.

All of the Super 250's I have seen have a McCulloch flat back carburetor with a choke, something that is rather unique amongst the Mac's.

Mark

 

[RandyMac]

Please educate me on the difference between the 250 and the Super 250.
Thanks
Willysmn

Mainly 7cc bigger, better and more ports, auto oil. Like comparing a store brand taco sauce to Tabasco.

 

[heimannm]

And extra holes in the air filter cover to give it better flow, or maybe to make it more aerodynamic?

Most also came with a full wrap handle, as did most of the 1-50 Series saws.

Mark

 

[willysmn]

Mac 250

The MC-20s go kart engines had a flat back carb, Maybe the -10s and -6s too.

 

[RandyMac]

The little Macs had a BullFrog carb.

Sometime later, McCulloch went to the cubes.

 

[heimannm]

Quite a few of the old McCulloch chain saws had the McCulloch flat back carburetors of one form or another. Most saw carburetors had a primer rather that a choke, the Super 250's and Super 550's were the only ones I have seen with the choke version in real lifel, or even from the IPL's that I have looked through. Most (all?) of the Kart carburetors had no choke and no primer, you were expected to manually pime them or choke them with your hand. Kart carburetors were generally larger (bigger venturi and throttle bore), called out as BDC, and were the "pressure pulse" type.

There are some similarities between the Kart carburetors and the saw carburetors, but there are a number of differences as well. Soom parts will interchange straight up, some require a little modification like the metering diaphragms, and some simply don't exist on one application or the other.

Mark

 

[heimannm]

Randy is showing a saw carburetor on the kart engine, as evidenced by the primer on that one...

The 10 Series "flat back" or Bullfrog carburetors were something altogher different again. In concept the single screw carburetors are very simple and can be effective if they havent corroded too badly. Biggest problem I have with the 10 Series flat back is the duck bill valve (63041) is no longer available and I have yet to find a good substitute.

Mark

 

[Mr. Bow Saw]

I have the 103cc geardrives covered, But not 10-10's,
Although i just got a LG2 bow saw. Doe's that count.


Lee

Bow saws always count but need to see a pic of it.

 

[RandyMac]

Bow saws always count but need to see a pic of it.

Pony up Lee!!!