Mcculloch 35A help. Any Mac experts?

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I did the carb of a 35A a couple of years ago... In the process I lost the check valve ball behind the diaphragm - better work on a large cloth ;). I found that the check valve ball used in the primer pump base of Walbro WY carburetors will work as a replacement.
Other than that: Try to remember each step and part during disassembly. I gave up on trying to imagine what each of the parts does, but the whole thing works if cleaned and reassembled the same way it came - even with a very baggy diaphragm.
 
stinkbait posted this in 2009
McCullochSection7FuelSystemServi-2.jpg

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I have a hard copy of those carburetor instructions but no good electronic copy at this time. The diaphragm in the fuel tank is the fuel pump, the large diaphragm in the carburetor body is the metering diaphragm. As Stephan noted, the 33/35/39 carburetors use a ball rather than a needle in the metering circuit.

If you play with it a bit you will see that when you open the throttle, is also lifts a push rod that admits more fuel; similar in design and operation of the McCulloch -10 Series flat back/bullfrog carburetors. The low speed adjustment is controlled by the metering needle in the bottom of the carburetor and the high speed adjustment by the lever in the top which actually limits how far the throttle is opened, controlling the rod that meters the fuel. Adjust the metering needle in the bottom to achieve a good idle then adjust the lever to run just slightly rich at high speed. Every 33/35/39 saw that I have run will never clean up out of the cut so they evidently designed them to run on the rich side.

You will discover that they are extremely reliable starting and running saws, yes they run pig rich and yes they are slow as molasses in the cut, but they do start and run. See your PM for some additional information.

The metering diaphragm, lever, and ball seat - note the lever is shown in the wrong position, the tab will be one the end of the diaphragm to hold it in place

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The bottom end of the carburetor and primer

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The bottom end of the carburetor and the low speed needle arrangement

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The fuel pump in the tank - first photo is the fully assembled pump minus the filter

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And all the parts in order...

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Add the fuel filter/wick

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More to come...

Mark
 
Wow! I had sent a reply before I saw your post here. Those are amazing! That trimmer is wild, I have yet to see that attachment. Is that crate factory or just something modified to fit? Either way those are great pictures. Thanks!
 
Ended up having to pull the head because the spark plug threads were stripped. There was no gasket under the head per-say but there was an alumnium shin plate. Didn't even have any sealant or anything. This saw is definitely a unique machine.

Anyone know the head torque?
 
Ended up having to pull the head because the spark plug threads were stripped. There was no gasket under the head per-say but there was an alumnium shin plate. Didn't even have any sealant or anything. This saw is definitely a unique machine.

Anyone know the head torque?
Probably something you'll have to calculate by bolt size thread type and tensile strength. Where's a machinist you need one
 
Yea they are tiny little Allen heads that go through the head shim and jug fins into actual nuts. The nuts fit just so-so in the fins so they're held for tightening. I think they're 3/16" or smaller. Appear to be grade 8 or close.
 
Ik exactly exactly what you are talking about, pretty common actually, mcculloch did that on their kart motors
 
I've never ran across an engine made that way. Just thought maybe since the whole saw was pretty unique, that maybe the other macs weren't that way either.
 
Yeah they are a fantastic design for making power, easy to mill the head and give it a bump in compression. I don't know if the rest of the engine is built like the kart blocks but that head design is. I'm sure youve already noticed that the engine is in there sideways. They have a bevel gear drive transmission which make all the attachments that much easier to build.
ADLM
 
Idk if you already have an ipl for that saw but if you want one @ray benson may have one, if not I'm going to get an electronic copy in a few weeks
ADLM
 
I've got the parts list. The service procedures are more what I need. Torque specs and such. I think I found the Mcculloch carb tuning procedure though. Of course I'm not sure how accurate it'll really be, but hopefully close.
 
Well today at work I cleaned up the bar and chain (lightly) with a wire wheel. Bar didn't come out as clean as I had hoped, but can you expect from an original 50's bar? I'm just lucky it was rusted to pieces.

Anyone know what size file this old 1/2" pitch chain uses? Or what the raker depth is supposed to be? It appears to be genuine Mac chain.
 
Well today at work I cleaned up the bar and chain (lightly) with a wire wheel. Bar didn't come out as clean as I had hoped, but can you expect from an original 50's bar? I'm just lucky it was rusted to pieces.

Anyone know what size file this old 1/2" pitch chain uses? Or what the raker depth is supposed to be? It appears to be genuine Mac chain.
1/4" round file for filing. Flat file for depth gauges in the .030" to .040" range.
 
Thanks, I'll see if I can dig up a file here at work. Took me a while to get the chain links free, but finally after a lot of KB88 penetrant, a vise and some determination every single one functions as it should. Appears the cuttters have plenty enough life left in them for the occasional chunk of firewood to show it off, BUT it is a shame that they don't reproduce the 1/2" chain anymore.

Now hopefully the thing will run!
 

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