Small Engines (Lawn Mowers, etc.): coil design, mcculloch eager beaver, coil design

Question
I have a McCulloch Eager Beaver chain saw. The coil (no points) is mounted with two bolts with a plastic tube around them with fiber washers, They  appear to isolate the bolts from the coil frame, I don't understand why.If one of thosse bolts was shorted to the coil could it prevent a spark?

Thanks

Rod

Answer
Rod
The reason for the tubes and the washers is too isolate the coil from the engine ground,and yes if they are touching the frame you will not get spark as it is grounding out. How a system works on the engines is when the engine is running and you shut off the switch it shorts it too ground,via a wire or a direct ground to the spark plug.