Chainsaw Repair

It's a continuity  test between the low voltage side and ground and the high voltage side and ground but most likely not your problem .

In most cases problems with a points type ignition can be traced to resistance in either the low voltage side connectons and more often to slight corrosion on the points .Might  look nice and shiny but remember you're dealing with a very small voltage on the primary side of that thing .

Often times too if the points have been burnished a very tiny piece of the grit from the sand cloth will prevent them from closing completely although they may seem to be .After you clean the points use a piece of printer paper to run through them a few times when they're closed to make certain nothing is caught in them .

Usually if you get any spark at all it's not the condenser or coil at fault .

It might not be a bad idea to clean every area the ignition parts making  contact with the saw engine because that thing is old as the hills and you have steel parts making contact with 50 year old aluminum  which is certain to have some oxidation on it .Aluminum is a conductor but strangely  enough aluminum oxide is an insulator and under a microscope resembles glass .

Generally speaking the points type ignition systems McCulloch used on the reed valve and 10 series saws are one of the most reliable systems ever made .

The earlier saws used the large coil where as the later series like to SP 105/125 used the smaller  10 series coils .

Much later of course they went to solid state being the PM 610 type which was used on saws such as the 805-850 , PM  610/650 and a host of others .These were pretty robust too as a general rule .

In all the 10 series saws I've worked ,which is many  only one appeared to have a bad coil .Oddly enough some time after I had replaced the offending coil which I saved I tried it on a mix match of saws to make another runner from parts and it worked .What was initially wrong with it to this day I have no idea . Magic maybe .