Weak Spark On One Cylinder

[Steve_S]

1946 A, weak spark on right cylinder. Assuming it isn't the plug or wire, is there any typical problem I can look for first? The cylinder hits maybe 2 out of 5 rotations while the left hits 100%. Holding the connector away from the plug, the spark on the right is smaller than the one on the left. It was running great until just recently.

 

[RandyB(MI)]

Only 3 parts are cylinder specific...plug , wire , cap. Nothing else would single out one cylinder over the other. Assuming we are talking about "out of the cylinder" testing procedure. Check resistance in both cap terminals or just replace cap. If you are testing this running then could be a lot of things.

 

[Lee B]

You have assumed too much and eliminated the prime suspect in my book - the wires. Renew them and see. No mention of magneto or distributor, but one thing you could do is turn the magneto drive 180 and swap wires in the mag cap connectors to see if the problem changes sides on you.

 

[Steve_S]

I should have mentioned it's on magneto. I've tried two wires but they were both old, and I can't find any locally so that's why I'm just assuming at this point. I'll peek inside the magneto while I'm waiting for the wires to ship. Thanks for the suggestions!

 

[Juicybusa2]

Partially fouled plug will result in the appearance of less spark when holding the wire away from said plug. 2cylinders with single barrel carb
tend to misfire at idle on the right cylinder and also run richer and foul the right plug more often and easier.

 

[Kelly Barnett]

Sounds like a possible condenser issue. I have seen where a tractor will stutter when running at idle (and other speeds) and one cylinder is weak spark. Because of the way the engine fires, the condenser does not have time to build up a decent charge before the points open up and wants the juice for the plug. It would benefit you to take the condenser out and check it for leakage / breakdown. Best of luck finding the issue.

 

[Steve_S]

That's a great point, about the odd timing of spark. If the right hand cylinder fires second then that could certainly be the issue. I'll be checking in to it this weekend, thanks!