chainsaw won't start - any ideas?

Factual Questions
1

I have an old McCulloch chainsaw - Model 10/10.

Until recently, it was possible to start the beast after much cursing and swearing and yanking the rip cord. Then it became necessary to have someone hold the throttle wide open AND go through a trial-and error fiddle of the mixture screw on the carby.

Now it will not start at all. When a workmate and I attempted a fix, we deduced that the motor is just not getting any fuel, despite the clear fuel line and very clean carby. If the cylinder is primed with some neat fuel, the motor will cough and fire until the neat fuel is burnt.

I have been trying to find something of an on-line manual that will help me troubleshoot the problem, but I am having no success at all.

Does anyone here have any hints, or links that I can be pointed to?

2

my grand-pappy taught me there are 2 main reasons an engine won’t start - no spark or no fuel.

you’ve obviously got spark, if you can start it by priming the cylinder.

so it’s most likely the fuel. pulling the cord also acts to draw fuel into the motor, though the exact manner is unknown to me. some smaller engines will turn over and “suck” fuel from the tank into the motor, while others have a small pumping action not unlike the fuel pump on a normally aspirated automobile. i’m not exactly sure how this all translates to a chainsaw engine, but i’d look at the “intake” action and/or the “pump” action.

3

The carby and motor combination on this chainsaw appears to rely on crankcase “suction” to draw fuel from the tank. Unfortunately, this does not appear to be happening, as we cannot see any fuel jettin into the barrell of the caby when cranking the motor.

What would be REALLY nice is an article detailing how the McCulloch 10/10 chainsaw fuel delivery system works, but alas I am not holding out much hope of finding such a luxury.

4

have you tried:

or calling 1-800-521-8559?

talk to Sandy - she’ll hook you up.

5

(meaning they may be able to provide specs or diagrams or something)

6

Thanks Dan. I have looked at the McCulloch website - there’s nothing there in the way of troubleshooting info.

As for the phone call - I live in South Australia. It’s just not worth me sitting up all night waiting on hold on an international phone call. My phone bill is big enough already!

Does anyone else have any thoughts?

7

I have one of those went through something like that. I put in a new spark plug. Also, did
you look on the machine itself for the starting procedure? Its very complicated.
Also use fresh gas/oil mixture (if it uses that) & check the compression.

8

Well I read an article in Field and Stream about chainsaws. The number one reason a saw gets messed up is by playing with the carb jets and adjustments. Chances are if someone has played with the carb needles they may have cranked them down too far and ruined them. You may need to have it rebuilt because once the needles are gone, they’re gone.
Here is the link to the article
http://www.fieldandstream.com/fieldstream/gear/article/0,13199,192545,00.html

9

Although the fuel line looks clear, it may be clogged at the fuel tank. Chainsaws operate in a very dirty environment and its not unusuall for lots of gunk to get mixed up in the fuel.

Check for some sort of filter, or screen at, or even in the fuel tank.

10

All you have to do is die in a graveyard on Hallowe’en and come back as a rampaging unstoppable goalie-mask-wearing mass murderer.

Those guys never have trouble with their chainsaws.

11

Check if the saw will start/cough if you spray ether/quick start into the air filter. This will rule out any valve problems.

Make sure you are using the correct fuel/oil mixture. Had a friend who’s dad bought this “special” oil that mixed 20:1 for every 2 stroke known to man. He spent days trying to fix his weed eater until I looked in the manual and found out that it needed a 40:1 mix, mixed up a batch with regular 2stroke oil and gas and bang, it ran fine (OK, I needed to re-tune it since he fiddled with the needles). If you don’t know the right mixture, mix Stihl or Husqvarna 2 stroke chainsaw oil at 40:1 and use this to test. It may be a little lean, but if it starts, this could be the problem.

If it coughs/runs with the ether but not with the new gas, remove the carb and try blowing through where the gas line is attached. If you can blow through it, gas should be able to go through it also. If not, there is a blockage somewhere in the system.

First try the mixture screw. Seat it mixture screw all the way in (turn lightly until it won’t turn anymore, BE GENTLE), then open it up 1 turn. (The owner’s manual may have this information). Also, like mg.greg said, if someone mashed your jets, you’re out of luck.

Most chainsaws have carbs that are designed to be used in all positions, so they don’t have float valves, just membranes to keep the fuel from leaking out. If the membranes are filled with dirt, they won’t let the fuel through.

If you still can’t get air through, try to follow the fuel’s path, and blow though each hole with compressed air. You should be able to find the obstruction that way.

Also blow through the supply hose from the tank to make sure it isn’t plugged.

If fuel is getting through, try to start it again and see if you fixed it. If not, chech the spark plug. If its wet, fuel is getting into the saw, but not burning. Could be too rich (try screwing the mixture needle in) . Try taking the choke off.

12

Thanks for the replies.

Unfortunately everything you guys have suggested has been tried:

  • the fuel line is absolutely clear of obstruction
  • the spark plug is dry
  • all apparent fuel passages through the carby have been checked and blown with compressed air
  • the mixture needle has been set at the position recommended above
  • the fuel is as per spec
  • the fuel filter and tank are very clean

I have come to the conclusion that there must be a component that provides the suction that draws fuel from the tank into the carby, before the piston action draws the fuel/air mix into the cylinder. But trying to find some ideas on how to troubleshoot this has been frustrating.

Incidentally, the Field and Stream link failed.

13

Buy a new saw. My Mac stopped working, and I saw a Sears 18" on sale for $89, then when I got to the store i got a 10% off coupon.

The Sears saw isn’t (probably) as good quality as the Mac, but it starts on the first or second pull and for the two or three times a year I use it, it’s plenty good.

You will probably spend as much trying to fix it or find parts to fix it.

now if you want to fix it out of sheer stubborness, or you’re just too flat broke to buy new, that i completely understand. Good luck in any event.

b.

14

ebay.com has lots of parts for your saw DVous…

15

Your sparkplug may be dry, but did you change it? Two-cycle engines are hell on spark plugs. As a regular user of a chainsaw, whenever it does quit cold-turkey on me, 99% of the time, changing my spark plug gets it going again.

John

16

I had a similar problem with my leaf blower.
The fuel line had pin holes in it, and the engine was suckung nothing but air.

17

If the fuel diaphragm has a hole in it, it won’t suck in gas either.

18

Air is pretty important, too. Have you changed/cleaned the air filter, DVous Means?

19

The sparkplug is brand new, and is producing a very fat spark. The fuel filter and air filter are both clean. The diaphragm appears to be intact.

I am almost at the point of giving up in disgust and buying a new saw.

20

Look through the carb and you should see the reed valve. This is a piece of springy metal that covers the hole. Press on it gently to see if it can move towards the crank case. If not, the valve is stuck and fuel can’t get in.

Again, did you try spraying fuel into the carb or air filter and see if it starts that way ?

If you can’t get it, make sure any saw you buy has a manual, and a good supply of parts. Also helps to have someone in your area who kows something about the type of saw you want to buy.

My recommendations: Stihl or Husqvarna. Best saws on earth.