Mcculloch MAC 130 solid state magneto question

[dragracerray]

I am fixing this saw for my neighbor. It fires if I put premix in the spark plug hole so I cleaned the carb and now I am worried about the magneto ground wire. This magneto seems to be insulated from the engine block. The mounting screws have rubber washers underneath them. Where does the ground wire go? I attached a picture of what I think makes sense. Does the ground wire go against the side of the magneto or does the ground wire go under the head of the screw? Thanks in advance for your help! Ray

 

[heimannm]

The insulators around the screws and under the screw heads are there for thermal insulation, not electrical insulation. The ground wire should go under the head of one of the screws to ground the coil. Ignore the red circle, it is just showing the leg on the fuel fitting for another issue.



Mark

 

[MacAttack]

The insulators around the screws and under the screw heads are there for thermal insulation, not electrical insulation. The ground wire should go under the head of one of the screws to ground the coil. Ignore the red circle, it is just showing the leg on the fuel fitting for another issue.

View attachment 826831

Mark

I had always wondered about those insulating tubes and washers as well!

My mini macs have them, my SP40 does not.

 

[dragracerray]

The insulators around the screws and under the screw heads are there for thermal insulation, not electrical insulation. The ground wire should go under the head of one of the screws to ground the coil. Ignore the red circle, it is just showing the leg on the fuel fitting for another issue.

View attachment 826831

Mark

Mark,
Thanks so much for the reply. So my picture is wrong. The ground wire should be against the magneto and not under the head of the screw?
Ray

 

[heimannm]

Under the screw head is correct as the screw threads into the cylinder and makes a good ground connection. The coil is effectively insulated from ground by the large green insulator between the carburetor and the cylinder and those plastic tube insulators.

Mark

 

[heimannm]

The photo does not show this clearly through the layer of oily sawdust.

Mark

 

[dragracerray]

The photo does not show this clearly through the layer of oily sawdust.

Mark

Thanks for the clarification Mark. That makes sense to me. Ray