McCulloch Chain Saws

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This type of thing loose.
0deaf10d91361ef4b5bcde16a2385a14.jpg
 
I know this is a long shot but could the exhaust be stopped up and not letting the exhaust out, just remove it and see what it does. That will keep it from revving up. The other thing I can think of is the reeds are not opening. I would suggest taking the reeds out and trying to run it that way. It should run without the reeds, not very good but still run. Something is not letting it flow the air it needs to run. Or could the lever that operates the butterflies in the carb be slipping on the shaft? I don't know, just some things to try.

Brian
 
Having lunch right now, then I will go check some stuff. I had the reeds out to reseal the plate and all looke fine/normal there. I will check the muffler and throttle plate and report back.
 
So removed exhaust, same thing. Checked throttle plate with a bent wire and can definitely feel it opening with the throttle gonna tear the carb out again, re do the pressure test again and go from there I guess. I'm really out of ideas and about to shelf this thing for a while.
 
I pulled the carb and I can see the reed valves and I can watch them flutter as I pull the saw over with the plug out. They are a biotch to remove so I'd rather not tear them all apart again if I can avoid it.
 
Ok, found my problem. I have a setup to pressure test but lack a setup to vacuum test (I know, I know). If I pressure test to 7 psi it holds great. If I back off and only pressurize to say 4 psi it wont hold at all. Long story short, I must have messed up the mag side clutch seal when I installed it. Oh well, I have another in stock at the shop, just gotta drivethere to get it.
 
Well ive had it for now!!! Gonna shelf this one for a while unless someone here has an idea of what else to do. I replaced the suspect crank seal again. Still no change. My carb kit arrived today from sugar creek so I went ahead and kitted the carb, now I cant even get it to run!!!! I cant even begin to express how frustrated and angry I am righr now!!! Paid $30 for the carb kit, have $150 into a bar and chain, not to mention what I paid for the saw plus the crank seals etc!!!!!!! Kinda fed up right now.
 
heimannm said:
Back a page to Poge's question...I was able to get mine out with a sharp pick starting under one end. I didn't have to worry about the piston or the clips because they were not going to be reused.

Mark
Click to expand...

Notched some circlip access. Definitely the ticket. Had to really heat up the pin bosses to get the wrist pin out though..., and still needed to use my arbor press. Clips came out easily with no deformity and will be re-used. Just a hair over 1/2" / 15mm.

0404171809_resized.jpg​
 
2broke2ride said:
Well ive had it for now!!! Gonna shelf this one for a while unless someone here has an idea of what else to do. I replaced the suspect crank seal again. Still no change. My carb kit arrived today from sugar creek so I went ahead and kitted the carb, now I cant even get it to run!!!! I cant even begin to express how frustrated and angry I am righr now!!! Paid $30 for the carb kit, have $150 into a bar and chain, not to mention what I paid for the saw plus the crank seals etc!!!!!!! Kinda fed up right now.
Click to expand...

That's definitely a carb problem. My first move, if that saw was on my bench, would be to swap in a known good carb, which is easy to do across the Mac line. Is the high side plugged up? I think there is a check ball under the welch plug.

On the other hand, there seems to be alot of spitback judging by what I'm seeing in that little collector thingy.

Chris B.
 
Thanks for the advice. Only known good carb I have is the Tilly thats in my 380, but it took me so long to get that saw tuned to where it runs like it should that I dont really wanna mess with it. I dont have any other saws with a flatback. I have a flatback on the shelf but it came out of a non running saw.
 
heimannm said:
The 550's did come with the primer flat back. Hard to say what that knob is for.

2broke - for you pig rich saw, the correct position of the metering needle is level with the body of the carburetor.

View attachment 566545

Older flat back carburetors had a sintered metal plug they called a capillary seal under the large welch plug, but most later ones had a plastic ball check valve. If the check valve is somehow damaged it would allow too much fuel to pass at low speeds. Fi the ball was missing altogether it might explain too rich at higher speeds as well as the ball does obstruct the flow somewhat.

If you want to pop that 1" welch plug out and check, I can send you a replacement welch plug.

How confident are you that the H and L jets are in fact the originals and of the correct length?

Mark
Click to expand...

Mark, does this offer still stand for the 1" Welch plug? I'm about at the end of my rope with this and this is the last place I have to go so would gladly take one if you can spare it.
Kevin Simpson
26 Tyler rd
Townsend MA 01469
 
Does anyone have the shop manual #103677 for a 4-30? I tried the 'beg for manuals' thread and they had the IPLs etc but not this one.
 

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