McCulloch Chain Saws

[Joe Crow]

Regarding my SDC carb. I disassembled the carb again and recleaned to no avail. Then I replaced the Diaphrams and gasket with the originals on the check valve side and the needle then held. So I assume leak was on the check valve side. I'm going to leave it that way and save the new Walbro kit for another day.

This is a single adjustable needle carb. Any advice on how to tune it?

 

[MacAttack]

Wow...how many McCullochs had a counter-balancer like that??

$350 in 1962 was a pretty penny!

I promise no more disparaging remarks about my beloved Macs....

 

[Rotax Steve]

Pretty penny you say? No kidding!

 

[MacAttack]

Holy smokes!!!!

 

[Rotax Steve]

You could buy a good used car for that today. Probably wouldn't run as good as a McCulloch but ...

 

[heimannm]

Joe - it will run pretty rich on the high side, but you can really lean on it and it will still have plenty of fuel. I like my PM55 with the fixed H, it cuts very well.

For the L, you want crisp acceleration so adjust it to where you have the best throttle response, then adjust the idle speed to insure the chain stops at idle. Usually 1 to 1-1/2 turns out from lightly seated. If you are far off that range I'd say something is amiss.

Mark

 

[eb20]

Wow ! Talk about the unicorn.

 

[Squareground3691]

850 New gaskets, carb rebuild, and reconditioning of a original Mac roller nose, she runs real good ,

 

[Syncop8r]

Just when you thought you'd seen everything...

View attachment 1249562

View attachment 1249563

I can't get past the starter configuration...

 

[heimannm]

The 33/35/39 models were first with that basic configuration, bevel gearbox to provide the change of direction to drive the chain.



The BP-1 took it one step further and put the points in the back so they could be serviced more easily.



Mark

 

[MacAttack]

The leaky, lean-running Tillotson HL is back apart on my bench. It has the "older" style metering lever and inlet needle. Does anyone feel strongly that I should swap it for a newer "hook" or "fork" style metering lever that pulls the needle open?

 

[heimannm]

They don't actually pull the needle open, it just takes the pressure off the needle allowing the fuel pump pressure to unseat the needle allow fuel to pass. The metering diaphragm doesn't move that much and it takes quite a range of motion to move the needle end of the fork that far.

If you haven't done it already, polish the tip of the needle and replace the rubber seat (assuming it has one).

Mark

 

[Syncop8r]

I can't get past the starter configuration...

It made me recoil in surprise.

 

[MacAttack]

They don't actually pull the needle open, it just takes the pressure off the needle allowing the fuel pump pressure to unseat the needle allow fuel to pass. The metering diaphragm doesn't move that much and it takes quite a range of motion to move the needle end of the fork that far.

If you haven't done it already, polish the tip of the needle and replace the rubber seat (assuming it has one).

Mark

For the life of me I can't find a thin-walled 5/16" socket that I can use to remove the seat. I have 2 brand new seats in kits. But...my problem is not enough gas on the Hi adjustment, and the needle / seat hold pressure. I might try raising the metering lever about 20 thousandths and see if it helps.

I wonder if it's possible that the rubber seat is swelled up and restricting the flow of gas?

 

[Jay Hansen]

For the life of me I can't find a thin-walled 5/16" socket that I can use to remove the seat. I have 2 brand new seats in kits. But...my problem is not enough gas on the Hi adjustment, and the needle / seat hold pressure. I might try raising the metering lever about 20 thousandths and see if it helps.

I wonder if it's possible that the rubber seat is swelled up and restricting the flow of gas?

I ground the tip of my 5/16" nut driver down until it would fit into the well and remove the seat.
If everything else seems right it's always worth a try to raise the metering lever a little to correct the condition you're describing. I think I might try for 8 pr 10 thousanths first though.

 

[MacAttack]

So I raised the metering lever about the thickness of the lever, probably a little more than I planned. It's late at night here now so I can't really rev up the old 450 without waking everyone, but I did start it and up to 1/2 throttle it runs great with no flooding, so I don't think I raised the lever too high.

Tomorrow I will try some WOT blasts and see if she'll 4-stroke.

Thanks guys!

 

[MacAttack]

Having fun in the shop so I snapped a comparison pic of Mini Me and Fat Bastard...