McCulloch Chain Saws

[Jethro 2t sniffer]

Probably even give it flush with degreaser

 

[JSMississippi]

Midway through my SDC-44 rebuild. Want to make sure I'm not overthinking things.

I've fit the metering lever and needle assembly and had to adjust the lever arm height. I don't have the little Walbro W shaped tool, but it is my understanding that I can just use a small straight edge across the two little raised bosses on either side of the arm? I bent the needle side of the lever a bit and have it now where the straight edge just barely depresses the arm when I put it across the bosses. Is this fine, or do I need the arm to be JUST under the straight edge but not touching?

 

[heimannm]

Just touching will be fine.

Mark

 

[JSMississippi]

Thanks Mark! I guess I am trying to understand this adjustment in terms of function when the engine is running. Knowing the how and why always helps me.

If it is too high (protrudes well beyond the bosses), less diaphragm movement towards the carb body under vacuum is needed to keep the needle off the seat -> rich/flooding potentially

If it is too low below the bosses, the opposite would be true: the inlet needle would stay on the seat more, causing lean out.

Am I thinking about this correctly?

 

[cdahl383]

I don't have a specific tool, I just use a small straight edge. I set it so it barely touches the metering lever.

If it's too high (sticking up) it will run rich. If it's too low (sunk down) it will run lean. The diaphragm will come in contact sooner with the lever if it's sticking up, so it will get more fuel than needed as it will start opening the needle sooner. The opposite is true if set too low. Won't open soon enough and will be starved for fuel.

 

[JSMississippi]

Working on gathering the last bit of parts needed for this 10-10S.

Need to figure out the air box seal. Mine basically disintegrated when I split the fuel tank halves.

January 1983 PM10-10 IPL shows the flexible seal PN 69564 (#24 in the diagram):
My 10-10S had this flexible style. FWIW my carb has an 85 date stamping.


I suppose McCulloch updated this seal somewhere in the mid-80’s. The September 1987 PM10-10S IPL shows the cork PN 219280:

I assume either style will work? I have some extra cork sheet on hand I may try. Does anyone have a picture of how far the seal extends in the front corners? Does it stop at these indentions?

Or does it extend all the way to and butt up to the angled portion of the fuel tank lip?

 

[vinnywv]

There is a groove on the top half all the way around it. The cork fits in that groove. No wider

 

[heimannm]

Joe's question is in regard to the air box "seal" and not the fuel tank gasket. The fuel tank gasket (cork or Viton) fits in a groove in the top half of the tank and that is pretty much all there is to it. The air box seal fits all the way up to fill that void, the idea of the seal is to enclose the airbox so that air can only enter through the air filter on top. No problem with the butyl, you just be sure to put enough in those corner voids to seal up with the tank. You can see in the illustration the cork or foam seals also have material designed to fill those voids.

This is the PM700 that I've been working on, someone attempted to seal the fuel tank and airbox with Threebond or something similar, but there are small gaps still in those corners. I will need to use some of the butyl caulking cord to press in there, or else try to carefully apply a bit more Threebond to the interior of the tank to effective close those little gaps. You can't see the openings in the photos, but you can see them live and in person as you move the saw around on the bench.



FW side, front corner of the airbox



PTO side, front corner of the airbox



Thanks to Joe for reminding me I still have a task to complete before this saw is ready for action. The Red Cote has been curing for a week and it almost ready, maybe on Saturday I will put fuel in the tank.

Joe - I have the butyl caulk cord on the list we discussed last night in our messages. I wear nitrile gloves when working with the butyl as it is pretty sticky and does not wash off easily...

Mark

 

[JSMississippi]

I see. So like this:

And there's nothing required on the side that is adjacent to the fuel tank, since it isn't open to outside air.