[wavebuy1]

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HELP!!!! The # 2 and 4 cylinders on my 85 1200 A are not firing. What do I look for?

 

[churchhillmike]

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Either one of your ignition coils has anternal short, or is shorting to ground. If you can disconnect the pulse generators wires from both of them, and remove the spark plug wires from the plugs, and disconnect the battery. Then using a multimeter, set on ohms scale, insert the probes into the spark plug caps 1 in no. 2 wire, the other in no.4 . then do the same to wires 1 and 3. your readings should be the same. Thats to find if theres an internal short. to find out if you have a short to ground, stick one probe into each spark plug wire, and stick the other on the frame. A low reading means you have a short, a high reading means youre ok. My guess is one of those coils is toast.

 

[Bike...and Dennis]

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churchhillmike wrote:

Then using a multimeter, set on ohms scale, insert the probes into the spark plug caps 1 in no. 2 wire, the other in no.4 . then do the same to wires 1 and 3. your readings should be the same.

Actually, cylinders 1 and 2 are on the same coil. 3 and 4 on the other. Impedence should be around 24k ohms.

If a coil is bad, the front two or back two cylinders will be affected. If cylinders 2 and 4 are not firing, it is more likely a fuel problem.
First thing you have to do is determine if it's getting fuel. If not, and to just one side like you say. It could well be a plugged secondary fuel line.