[MSattler]

Last year the bike would act like it was out of fuel, the rear cylinder would shut off, then turn back on. So over the winter, I put a funnel into the fuel hose to the carbs and put seafoam in, soaking it for about 3 months. Didn’t help. So I pulled the carbs and that didn’t help. I pulled the spark plugs from the cylinder and the sound didn’t change. There was air coming out of the exhaust, but it never got hot. I was thinking about buying new coils since two of them are $30

 

[Spockster]

Last year the bike would act like it was out of fuel, the rear cylinder would shut off, then turn back on. So over the winter, I put a funnel into the fuel hose to the carbs and put seafoam in, soaking it for about 3 months. Didn’t help. So I pulled the carbs and that didn’t help. I pulled the spark plugs from the cylinder and the sound didn’t change. There was air coming out of the exhaust, but it never got hot. I was thinking about buying new coils since two of them are $30

Check for spark on that cylinder?

 

[MSattler]

There’s no spark on the rear, at least from what I could tell. I pulled the plugs, then put them against metal while the engine was running and there was no arcing

 

[Spockster]

There’s no spark on the rear, at least from what I could tell. I pulled the plugs, then put them against metal while the engine was running and there was no arcing

Check for voltage on the positive side of the coil. The coil can be ohm tested also.

There's a bit of history of losing connection to the CDI, a broken wire.

 

[Green1]

You might want to swap the front and rear coil to see if the coil is bad or if it is a wiring issue. Especially since you have one coil that is firing. My car crowd does that all the time now since every cylinder has its own coil.

 

[MSattler]

Check for voltage on the positive side of the coil. The coil can be ohm tested also.

There's a bit of history of losing connection to the CDI, a broken wire.

So do I just put the voltmeter on the 50k range and put the red lead in the spark plug boot and the ground the black? The rear one looks like a pita to get to

 

[Spockster]

So do I just put the voltmeter on the 50k range and put the red lead in the spark plug boot and the ground the black? The rear one looks like a pita to get to

Use the 1K setting.

Primary winding... Disconnect both primary leads (hot and ground) Check across the two terminals. Should be 1.8 to 2.2K.

Secondary winding... Remove both spark plug caps. Test between the ends of both spark plug wires. Should be 19k to 29k.

Check the secondary first, if it fails the primary test isn't necessary.

 

[Spockster]

Use the 1K setting.

Primary winding... Disconnect both primary leads (hot and ground) Check across the two terminals. Should be 1.8 to 2.2K.

Secondary winding... Remove both spark plug caps. Test between the ends of both spark plug wires. Should be 19k to 29k.

Check the secondary first, if it fails the primary test isn't necessary.

Just to be clear, you have to remove both plug caps from the spark plug wires before testing. Because the cap itself has a resistor in it, which would affect the test.