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Followup To
Question -
I've cleaned & checked carb., had ignition module tested (twice) and cleaned up starter motor to ensure at least 250rpm at cranking. Checked ignition switch and even disconnected grounding lead at magneto coil. Coil has correct clearance to flywheel and magnet is strong enough to do the "screwdriver test". Fitted new spark plug with correct gap but it STILL won't fire! I can't even detect a spark. No sign of shorting from HT lead. Intake & exhaust valves work OK and compression is reasonable.
What have I missed? Any suggestions would be very welcome, thank you.
Answer -
Dis-connect the ground wire from the coil and test for spark. The ground wire is the small wire connected to the coil.
IF the engine starts you will not be able to shut it off with the ground wire dis-connected. Check for spark with the spark plug removed from the head. The plug will have to touch the metal engine in order to check for spark.
Let me know what you find.
Eric
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Thanks Eric,
Yes, I did try that and couldn't find any spark. About the only thing I haven't checked is whether there is a break in the HT lead, although it would probably need to be a significant gap to produce no spark at all. My multimeter did show a resistance from HT lead to ground (I think from memory it was somewhere around 2500 ohms) so I presume the secondary coil and HT lead is OK.
Any further suggestions?
Many thanks,
Bruce.
AnswerSorry it's taken so long to respond...the allexperts site has been having trouble.
It must be the coil then. I rarely find bad coils but it happens. The resistance sounds about right, but if you isolated the coil by dis-connecting the small ground wire and still had no spark then the coil is bad.
Believe it or not I actually found a bad coil today. I spent several hours isolating the problem but finally found a used one and it worked fine. The main difference between you problem and mine was the engine would start but not accelerate...very weird problem. Different coil and it works great.
Do you have any friends that might let you borrow a coil to make sure it's bad?
Let me know.
Eric
