McCulloch Pro Mac 610 Problem

I recently picked up a few chainsaws at a local auction two of which a McCulloch saws.

I am having a bit of a problem with the old Pro Mac 610. When I first got it home I could get the thing to run any more than a few seconds so I pulled off the air filter and noticed that the fuel line was all hard and brital and in one spot was leaking fuel everywere so I replaced it and sure enough it start on the the third pull.

It seems to run like a charm, idols perfectly in fact it idols somther than any of my other saws!!
My problem is as soon as I try and cut a piece of timber it just dies. At first I thought it might have been a clutch problem but it does not sound like it is slipping.
It sounds like the thing labours when it is under load like someone is grabbing hold of the chain (not that you would of coarse :o)

I don't have a guage to check the compression on it but it doesn't feel to bad when you try and start it.

I pulled the muffler off to check inside the port for any piston scoring but it looks quite good.

If it needed a new piston ring in it would this be a sympton that would show that

Could any Pro Mac users shed any light??

Regards,

Paul

I will try it this evening and let you know.

Thanks again,

Paul

I took off the muffler and gave that a good clean out but it really wasn't all that bad I thought.

I also took the Carb off and opened it up, I didnt strip the whole thing down but I opened up either side of it and actually found it had a few remnants of the old Fuel Line so I cleaned all that out. Stuck it all back together and once again it seemed a little bit better but still does not seem to run all that hard when cutting.

The Chain could probably do with a sharpen but it's not all that bad, I have got a little 48cc homelite that seems to go harder than the Pro Mac so there must be something I am missing.

There is one thing that I did not do when I cleaned out the carby, there was a small brass wire filter with a Steal ring holding it in place on the diaphragm side which I couldn't seem to get off. I was a little hesitant to put pressure on the thing in case I lost/broke it but one would assume if it was dirty it would have been on the outer side of it not inside correct??

One thing I did not mention in my first post is that once you first get it started if you try and hit the throttle it will bog down real bad and if you give it to much it will just stall. If you wait a minute or so till it warms up it is ok after that.

I am really not sure what to do next, any idea's would be a great help!!

Thanks again,

Paul

Thanks for replying!!

I will have a bit of a play with the mixture settings today and see what happens..

Just as a matter of interest was is the recommended fuel mixture for these old Macs??

Is it 40:1???

The Fuel line was defantely shot in fact when I took the top cover off the carb there was a peice of it sitting on the throttle valve. So it may just need a cleanout.

Looks like a day of working on saws, I have to put a new Piston and Ring Set in the Jonsered as well.

The mrs's will be happy :o)

Will let you know how I go..

Regards,

Paul

1 - Try opening the high speed mixture adjustment ¼ turn at a time - test operation after after each adjustment.

2 - If after about 1-1/2 to 2 turns out on the high speed screw it still isn't right, fish the fuel filter out of the tank and see if it's plugged. Clean or replace if needed.

3 - If that doesn't do it, the carb probably needs to be torn down, cleaned and it's two gaskets replaced.

Also - when you had the muffler off, did you thoroughly clean it out? Carbon buildup inside the muffler and on the spark arrestor screen can cause the problem you are experiencing.

Note: If the piston ring was worn or the crankcase leaking, the saw would be hard to start and it would idle poorly.

Good luck!