Home › Forum › Ask A Member › 1926 Johnson A-25 Spark Issue???
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Tom.
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May 31, 2018 at 3:57 pm #10107
My A25 has spark on only one cylinder, the other side has a healthy blue spark, I am using a spark checker. Both wires are new and show continuity from the coil to the plug. I am not very knowledgeable on ignition systems so need some help. Using a multi- meter should I show a reading between the two plugs? (I show nothing) I always thought there should be but I have another A25 and an A45 that also show nothing between the plugs and fire right up 😕 Thanks for any input or advice to send me in the right direction.
I might add I have several other A motors that do show a resistance reading between the plugs.May 31, 2018 at 5:46 pm #77145Be sure to ground one side when checking spark on the other. Test one side at a time. Let us know the results.
If you’re getting spark in one side and no continuity, it’s likely that you have bad contact where the wire butts up against the brass tab at the bottom of the coil. You’ll have to remove the bakelite nuts that hold the wires in and clean the tab and the end of the wire. It’s certainly possible to get spark with this condition, but there will be arcing between the end of the wire and the tab, and that will eventually lead to problems.
Don’t try to remove the coil at this point. Let’s go through some other stuff first.
Tom
June 1, 2018 at 2:44 am #77188Thanks Tom, I did check one cylinder at a time and grounded the other one. I should say that when I got this motor the plug wires were not connected to the coil and there were no tabs on the coil showing but seems had been replaced by a contact of solder which I used to connect the new wires. I know this is not correct and am thinking that this may be my problem. If so is there any way to find out or is there somethig else to look for?
June 1, 2018 at 11:32 am #77201This is a little odd… There is only one secondary winding, which means the secondary coil has both ends going to a spark plug. The only way to get spark from one, is to ground the other. So that makes me think that the one with no spark is grounding somewhere. It’s possible that spark is jumping from the solder blob to the mag plate where the wire connects, or the wire is cracked where it comes out of the mag plate and grounding there.
Can you remove the bad wire? If so, remove the wire, then ground the good wire. In a dark area, rope the motor over while looking into the hole where the bad wire was. If you see a spark, you know the bad side si grounding to the mag plate. Don’t do this too many times, it’s not good for the coil. If you don’t see a spark, try replacing the wire with a new one.
Good thing is that the coil is likely good. You just have to find out where the "bad" wire is shorting to ground.
Tom
June 1, 2018 at 5:24 pm #77219Tom, I followed your instructions except replacing the plug wire. I removed it and went over it thoroughly and could not find anything suspect. Buttoned everything back up, grounded the other wire and spun it over. Looking through the hole for the plug wire saw nothing. Re-soldered the plug wire also re-positioned it slightly to be sure it was not making any contact with the plate and put everything back together. Then the big test, great spark on both cylinders 😀 Put a little fuel in the tank, gave her a couple of pulls and away she went!!! Next will be a water test but that will be for another day. THANK YOU TOM!!!!!!!!!!!
June 1, 2018 at 5:55 pm #77220Great news, thanks for getting back to us!
T
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