McCulloch Pro Mac 850 Not working

[leeg]

Hi All,

Let me first say it is an honour to be here.

I Recently purchased a Husqvarna 445 to replace my Mcculloch Pro Mac 850 that died. Since then I have done some research on the Internet to do with Chainsaws and found this site. Since then I have been reading through the different fourums and am amazed at the wealth on knowledge on here and have already learnt a few things. I hand sharpened my first Chain the other night, havent tested it yet though....

Now since having the 445 I'm kinda already missing my PM850. (Probably something about the 40cc or so difference in the two saws, hehe) ( I was given the PM850 5 years ago and had to purchase the 445 and couldnt justify spending more for the verry little firewood I cut)

Anyway I will get on with it.

My Mcculloch PM 850 wont run. It starts and then runs for about 2-3 seconds then cuts out. I can do this for as long as my arm allows pull starting it and each time it is the same result.
There is also fuel/oil leaking out the exhaust. At first I thought it may have been something like a fuel blockage but then took it somewhere and they said it could have been a number of things but wasnt willing to look at it at all because there would be no parts around.
Parts are virtually impossible to get here in Australia for the older Mccullochs.

Now the questions.
1. Any ideas what the problem could be?
2. Any ideas where can I get parts from either in Australia or overseas for this saw?
3. is it fixable? or just wouldnt be worth the hassle at all?

Thanx guys

[sawguy21]

First of all, welcome aboard. You are right, there is a wealth of information here.
The secret is a systematic troubleshoot. First of all, does it have good spark? I mean a fat blue arc across a tester (preferable) or a new properly gapped plug.
Second, does it have good compression? Suspend the saw by the starter handle, it should not creep down. If there is any doubt, remove the muffler and have a look at the piston and cylinder through the ports. There should be little if any scuffing and no scoring or galling (metal transfer).
Now give it a snort of fresh gas mix and see if it fires. If it burps and quits you have a fuel supply problem. Check the fuel and impulse hoses for hardening or cracks. Change the fuel filter. Has it sat for a long period of time? The carb may need an overhaul. All else fails, have a knowledgeable tech pressure test the crankcase tocheck for leaking seals or gaskets.

[amberwood]

Leeg...another from Aus?  Welcome to the forum!

DTR

[leeg]

Thanx guys, glad to be here.

The saw wasnt used everyday, it tended (on Average) to get used a couple of times a month (Couple of day at a time), probably not the best thing for it.
The day it stopped I had been using it it was running fine. Think I stopped to refuel & oil (cant remember exactly why I stopped) but since then its hasnt worked.
Without a doubt a new spark plug wouldnt hurt. The fuel filter has been cleaned but not changed.
The Carb could probably do with an overhaul, in the 5 years I have had the saw it has new been serviced, not sure if it ever was before that either. (Yes I can hear you guys cringing, thats why I'm on here, to find out more about chainsaws and how to maintain them *Properly* )
Not sure about the compression, I think its okay but will check when I can get my hands on the saw.
If it was a fuel supply problem would I be getting fuel leaking out the exhaust? It never did this before now

Thanx,
leeg

[Al_Smith]

 The 850 Mac was one of the last of the large 10 series designed saws .As such it has no impulse line per say but the impulse comes directly from the crankcase to the carb via a small port next to the intake .

What you have is a classic fuel delivery problem due to a faulty carb or faulty or plugged fuel line .

A rebuild kit for that model is relatively cheap ,it could be a Walbro SDC or a Tillotson Hs . Rebuilding one is pretty straight forward plus tutorials on the specific can be found online via the carbs manufacturer .

Nothing to it ,I've one or two myself  ;) Fact is I just ordered 18 carb kits the other day .

[Al_Smith]

  If it was a fuel supply problem would I be getting fuel leaking out the exhaust? It never did this before now

Thanx,
leeg

I didn't catch this last part when I first read the post .You definately have a carb problem .No doubt the diaphragm in that thing is as stiff as board . It happens ,get the rebuid kit .

[leeg]

Thanx for that. I would say you are right in saying the diaphram will be stiff as..

Do I need any special tools to rebuild the carb?
I've also read that this model came with a couple of different types of carb, silly question here, but am I correct in saying that if I look on the carb it will tell me what make/model of carb I have? from there I can then find what kit is needed.

Are you able to tell me what the 'large 10 series' is?

Thanx again

[Al_Smith]

? Are you able to tell me what the 'large 10 series' is?

Thanx again

The 10 series of McCulloch saws used a type of semi closed ports that went up to the transfer ports in a spiraled type of configuation ,in conjuction with a windowed piston design . The most famous or most recogonized would be the 10-10 which ranks as one of  the longest production runs of any chainsaw ever made .

The super pro 80 ,81 and 850 etc .are largest of these,the largest of the old school McCulloch piston ported engine design .Still good old old cutters and over 30 years old .