McCulloch Mac 7-42 factory card settings

[chrisbrooks]

good morning Gentlemen

 

would any of you know what the factory carb setting are for a McCulloch mac 7-42 ?

[chrisbrooks]

can anyone help me please as i have a saw that is refusing to start

[peatff]

Turn the screws in till they seat gently, don't wrench them tight. Then try 1.25 full turns out on each as a start Chris. It's not necessarily what they recommend but it's not going to be miles out. Have you definitely got a spark and compression if so try a spoonful of neat fuel straight down the plug hole and heat the plug on a gas ring or blow torch and stick it back in quickly then try a start with no choke.

[chrisbrooks]

Is that 1 and a quarter turns

[cornish wood burner]

Is that 1 and a quarter turns

It is.

[spudulike]

Personally I would check the piston out by taking the exhaust off and looking at it through the exhaust port.

 

I generally find that the owners of these saws are weekend warriors and have issues grasping what 50:1 fuel to oil is and also use old fuel mix in them which generally seizes them leaving them with low compression.

 

If the saw has a nice lot of compression and the piston is OK then the most likely cause for lack of start is the metering arm height not letting fuel through to the metering section in the carb or the carb just needs a good clean up and check over!

[chrisbrooks]

Hi spud i have the off and cleaned it so piston will be the next thing any idea what sort of reading i should get on my compressin tester spud

[spudulike]

Hi spud i have the off and cleaned it so piston will be the next thing any idea what sort of reading i should get on my compressin tester spud

 

Generally, the majority of saws pull 150-170psi but it can depend on the tester used. If you are using a Gunson Hi Gauge then this is typical after 5-6 pulls with 70-90 on the first pull.

 

If you read 140 or under then check the piston out as previously mentioned - a badly seized machine will only pull 50-90psi, you typically need 130+ for combustion.