The three things the engine needs to run are spark, fuel in the correct quantities, and compression. Check spark on all the cylinders by taking a spare plug and leaning it against the block and running the motor at different rpms to see what sort of spark you're getting. You could also do this with a timing light if you have one but I prefer the plug method as it's lets you judge the intensity of the spark. A yellow spark and lots of misses is obviously bad and likely the culprit. In that I'd try what Joey suggested before I go about anything else, change the wires and plug boots and see what happens. They're cheap and corrosion never sleeps.
If spark looks good I'd next do a compression check on all cylinders. If one cylinder has a dinged valve or a cracked ring and can't work up much compression the mixture also won't fire. This you need a tool for. Take a spark plug and go down to Autozone. Ask them for a compression tester and make sure they have an adapter that matches your spark plug thread. You can rent those tools for free with a retainer payment that they return in full once you return the tool. Once you've got that pull all the plugs out and hook the tester up to one cylinder at a time. Open the throttle all the way and crank it for a good 4-5 compression cycles until the gauge maxes. The cylinders should all be within about 20 psi of each other and in the neighborhood of 150psi. If one or two reads unusually low then you've got some engine work ahead of you. If these both come back good then the carbs are likely at fault. This is going to much harder to diagnose especially since the carbs have already been cleaned. I'd suspect the enrichener (choke) is stuck open on those carbs and flooding it but nothing but a good tear down and examination can confirm or deny that. Let us know what you find. -- You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/nighthawk_lovers?hl=en.
