Just like the title says, returned from a 200 mile ride hopped a few speed bumps now I have one cold header. I have compression, fuelto the carb bowl, clean jets, and spark at the plug but when it's all together I only have three cylinders making heat..... anyideas,CDI box, regulator?

Thanks!

 

Have you checked the connections to the spark unit? Is there any water or dirt inside the spark plug wire cap? Is it seated tightly?

 

if you have fuel air and spark you should have fire, if you are checking the plug with that plug wire ? if you are pulling the plug oput to check it and have spark then when you put it back in nothing, you may have a broken plug wire, when it is pulled stright out it may make contact and when you put it back in the bike you may bend it at the right spot and loose connection? Just a thought.
I would not think it is a coil because youwould not have spark anytime.