Chainsaw not sparking!

CaptainLiberiousAugust 12, 2013

Hi folks,
I've been given an old McCulloch chainsaw that I'm trying to get working, the problem I'm having is it that it won't spark. I've put a brand new plug in to eliminate that possibility, I've tested the coil with a multimeter and it produces between 12 - 15 Volts on the AC setting, but nothing on the DC setting. Are these supposed to have some kind of rectifier on them or does it not matter whether its AC or DC?
I've had the coil off and cleaned the pickup, and cleaned the magneto with wire wool. Tested the coils resistance, its about 10k ohms. Not sure what else to try now so any suggestions would be very much appreciated!!
Thanks

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loger_gw

I would say DC but I have not ever known it to be tested that way. Did you try testing with a grounded plug to the metal cyl or in-line spark tester?? Otherwise, I have used coil testers that are AC powered that will fire the plug through the coil (if the coil is good). If it is Magneto ignition (points under the flywheel) vs electronic, have you checked the condition of the points contacts and gap spec?? Attached is an Electronic vs Mag Sys.

Please post a Pic or pics of the matter or links to the model saw.

    Bookmark   August 12, 2013 at 7:01PM
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CaptainLiberious

Hi mate! Thanks for the reply, there doesn't seem to be any model number on the saw but I've attached a photo of one that looks similiar. This one has points ignition it turns out, I pulled the flywheel off last night and cleaned and set the points, still not sparking though. Should there be connectivity between the two small wires that come from the coil?
I'm also not sure if the magneto's alright, there are two small magnets next to each other on one side, and they're quite strong, but there's a bit on the opposite side which looks as if it should be magnetic but isn't, could this be my problem?

    Bookmark   August 15, 2013 at 9:23AM
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loger_gw

1. Did you ck the point gap for .020 (or to spec) open at the widest point?

2. Did you ck the cleaned points with the multimeter to know you had good contact between pointâÂÂs contacts?

3. Please show a pic of the magneto area showing the two small wires in question and missing mag in same pic if needed (in one easy attachment vs html code method)

4. There could be a counter balance of weight on the opposite side of the flywheel, the pic should tell.

5. Is the air gap fixed or adjusted after the steel wool cleaning? Set gap with an index card if adjustable, with magnet pulling the coil, rem fly and tighten (with drag on card.

6. Any history on what was done to the saw before it stopped or you started testing?

7. I tried to find a youtube on adjusting the Mini MacâÂÂs points. If you find one, Share.

    Bookmark   August 15, 2013 at 2:11PM
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CaptainLiberious

I'll post a picture or two tomorrow, hopefully you'll notice something that is obviously wrong. One thing I've noticed is that one of the 'prongs' on the pickup sits considerably closer to the magneto than the other, and this can't be adjusted out.
I set the points to 0.18, which I read elsewhere was right, but will reset them to 0.20. I did check with a multimeter that there was good contact, and positioned the coil using the business card method. The guy who gave me this saw said it was working when he last used it (about 6 years ago), so there can't be anything seriously wrong with it.
Thanks for the help!

    Bookmark   August 15, 2013 at 2:22PM
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loger_gw

Good Work/Experimenting!

1. Go with the .018 if it's confirmed to be correct. The .020 is an old school standard that I have always used. That should only through your timing or kick-back vs no fire.

2. Have you tested the condensers or replaced them with known good ones. I have a condenser tester vs knowing a backyard test. Condensers are cheap and usually replaced if suspects and very seldom bad. If you have a close supplier, purchase one new are two used from a mechanical dead working compatible motor or switch a new vs breaking the Bank.

3. To all the troubleshooters, what is a basic backyard test for testing condensers vs replacing them?

    Bookmark   August 15, 2013 at 6:59PM
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chas045(7b)

I just happen to have one that looks like yours that I scrounged up when someone was throwing it away. It is an 'eager beaver'. Sorry I don't know anything else about it yet.

    Bookmark   August 16, 2013 at 2:37PM
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CaptainLiberious

hi guys,
Finally got some pictures taken so here they are, I think I'll have to do this in 3 posts.
This one is of the two magnets on one side, marked 'IGN' on the magneto

    Bookmark   August 19, 2013 at 5:06AM
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CaptainLiberious

And heres a pic of what looks like a magnet on the opposite side, but isn't actually magnetic

    Bookmark   August 19, 2013 at 5:10AM
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CaptainLiberious

And here's a picture of the ignition coil setup. There is connectivity between the two small coil wires, does this mean that power could be bypassing the points and going straight to ground through the shorter wire? However I've tested a couple of motorcycle coils I have and the smaller connections are joined together, so I don't know...
There only seems to be one condensor on this saw, do you have any idea on how to test it?
Thanks for all your help so far, forums are great!

    Bookmark   August 19, 2013 at 5:15AM
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loger_gw

Another Pic would help me, straight down from the top with the black cover off (to see the points and full dia of components below the flywheel. Please show with the points open and coil air gap showing if possible in one close full magneto dia shot.

IâÂÂll attempt to see a .018 -.020 gap on points vs .18. See if the coilâÂÂs air gap is fixed or approx .010 and wiring matter mentioned. LOL. Someone might be able to see enough to help.

    Bookmark   August 19, 2013 at 11:42AM
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CaptainLiberious

I think I may know whats wrong with it! There seems to be a bulge on the magneto at the 'IGN', the gap between pickup and magneto gets larger when rotated but smaller just as it goes past the two small magnets. Is this likely due to the magneto or bent crankshaft?

    Bookmark   August 20, 2013 at 9:47AM
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