Topic: no spark on #2 cylinder

[plug1]

1975 cb400f. #3 fires fine. When I hold the #2 plug to the engine housing I can see a tiny spark between the plug and the engine but no spark in the gap. I tried swapping known working plugs and wires and still nothing. The coils are new dyna 5 ohm, reading 4.9 ohm on multimeter. Stock points. Thanks.

[bollingball]

If you changed# 2 & 3 wire & plug and # 3 wire & plug was good I would think it has to be the # 2 side of the coil. Are you sure the connections are good and tight?

[plug1]

I put #2 wire and plug on #3 side of coil and got a nice spark. I put #3 wire and plug on #2 side and still nothing. It seems to me the coil is bad. It's only been on the bike a few months though.

[HondaMan]

Check the plug cap resistance for both caps. Stock on CB400F was 10K ohms each, with 11k ohms being considered "burned out". If they measure more than 800 ohms different between them, the spark will not distrbute evenly from the coil, moving mostly toward one plug.

If you replace the caps, use the NGK 5k (5000) ohm variety for longer life and cleaner plugs. You can get them at most bike shops, but be sure to check the resistance. They come in 0 ohm, 5k ohm, and 10K ohm types.

[plug1]

What's the method for checking the cap for resistance? It doesn't seem to be plugs or wires but I'll try it. No matter which plug or wire I use, it's not getting any spark. I tested it with #3 wire removed and still nothing. I tried swapping with the other coil and nothing. I have good spark on all other cylinders. Is there a more accurate way to check for voltage at each port on the coil? One test lead inside port, other to ground?

[bollingball]

Take the cap off the wire. put one lead of your ohm meter in one end of the cap and the other meter lead in the other end of the cap to check resistance.

[HondaMan]

What's the method for checking the cap for resistance? It doesn't seem to be plugs or wires but I'll try it. No matter which plug or wire I use, it's not getting any spark. I tested it with #3 wire removed and still nothing. I tried swapping with the other coil and nothing. I have good spark on all other cylinders. Is there a more accurate way to check for voltage at each port on the coil? One test lead inside port, other to ground?

If you have stock Honda coils and the spark wires are removable, the wires are broken. You need new coils. The wires are part of these coils, non-removable.

[plug1]

They're Dyna coils. Purchased them from Z1 Enterprises. I've come to the conclusion that it's a faulty coil. Hopefully I can exchange for a working one. Thanks.

[Deltarider]

I've come to the conclusion that it's a faulty coil.

How?