87 Marathon 2 stroke with intermittent spark

[Mulligan aman]

I’m working on a 1987 marathon that shows spark intermittently. Is this likely the igniter? I’ve replaced the coil and plug. It shows 100 psi for compression and fires occasionally but not consistently.

[slonomo]

Originally Posted by Mulligan aman

I’m working on a 1987 marathon that shows spark intermittently. Is this likely the igniter? I’ve replaced the coil and plug. It shows 100 psi for compression and fires occasionally but not consistently.

When you say "it fires occasionally".....do you mean it will try to start? Or you are actually seeing "spark" on a spark tester?

You have primary ignition = pulsar, ignitor, cdi, etc = this provides the signal
Then you have secondary ignition = coil, wires, plugs = this produces the spark

There are testing procedures for each part if you want to get technical. A service manual will have all the procedures and specs. Sometimes throwing parts at it doesn't get it done, that's when you get the multimeter out.

100 psi seems a little low, what is the spec in the manual?

[Dabble Inn]

Factory compression is 120lbs, my new rebuild was only about 115lbs..... It should run with 100lbs, but yes that's a little low.

[slonomo]

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