McCulloch SP81 Coil & Spark issue

[ozziechainsaw]

So I have had a SP81 laying around for a while and decided it was time to get it running. All it needed was a coil...or that's what I thought.

I replaced the coil with a good coil I had on my Pro Mac 60 which is a perfectly good running saw. But nothing, no spark at all. So I removed it and checked everything and found the wire from the condensor to the coil was almost broken, so replaced that and still nothing.
I removed the flywheel thinking it was the points. They look good and the gap was a tight 14thou. I just cleaned them and put the flywheel back on and still no spark. So I changed the condensor hoping and and praying that was the problem, but NOPE still no spark. So just incase the coil wasn't as good as I thought I put it back onto the the Pro Mac 60 and guess what,,,,,perfect spark.
The coils look identical and so do the flywheels.

I must be doing something wrong. Any suggestions at this time would be very much appreciated.

Cheers
Justin

 

[heimannm]

Did you disconnect the stop switch at the coil? If the stop is grounding all the time you will have no spark.

I had one set of points in a 10 Series that would not work even though they checked out fine, I never did analyze why exactly I just tossed them...try switching the points from the SP60 as well and make sure the connection outside the points box is not grounding on anything.

How do you test the condenser? Look at the attached document for some help...if you meter does not have the capacitance function just check resistance and switch the leads back and forth...you should see a little blip in the meter each time you switch as the condenser discharges & charges through the meter as the polarity changes.

I normally set the point gap 0.018-0.020" and the coil to flywheel @ 0.010".

Don't rule out the spark plug (although rare, spark plug failures do occur) and make sure the spark plug lead has a good connection under the boot, I often find faults at that location. Normally you can just clip a little bit off the end of the plug wire and reinstall the connector making sure it has good contact with the wire inside.

Mark

 

[GoBigRed]

Did you break out a meter and check everything. Capacitor, high and low side of the coil? Continuity of the of the plug wire from coil to cap?

ive picked up a few saws for cheap that had no spark and both where situations where the plug wire was disconnected from the cap. Cut it back and reattached and it worked.
Im not sure what resistance is for the coil measurements but check as see if you have something on both sides and start there.
If the coil came from a running saw then my guess would be the capacitor. If the capacitor is good then check the kill switch. Happens more often on homelite toggle switches but they can ground out even when in the on position.

 

[heimannm]

10 Series Points Ignition

Resistance – 1 Ω Primary

9-10K Ω Secondary

Inductance – 2.4-2.7 mH Primary

9.4-10.33 H Secondary

9.17-10.06 H Primary to Secondary

These figures have been derived from measuring a number of good known coils.

Condensers are normally in the range of 0.2-0.22 µf

Mark

 

[L34]

Are the flywheel magnets Ok?

 

[ozziechainsaw]

I will go and check again everything that has been suggested.

I did swap out the condensor from the Pro mac 60 and installed it into the SP81 and then all of a sudden I have spark. So I put everything back together and now no bloody spark again.

I know the coil is a good coil as it is was in my running Pro Mac 60. I just don't understand why it won't run/have spark.

Justin

 

[Maintenance supervisor]

Same saw, I put together from parts . I didn't want to diagnose all the "parts " as I was assembling the saw . 18.00$ later runner!
I've only resorted to the electric chip a couple of times but I've gotten very good results with them every time.

 

[ozziechainsaw]

I didn't get a chance to go back and check everything again, but when I do I am going to test everything including the condensor and also swap out the points.

 

[tomalophicon]

The suggestion of the kill switch would be the first place I'd start as it's an easy test.