Bike running rough, puffing black smoke after carb rebuild - Motorcycle-Journal Forums

ghunt81 · 09-23-2008, 09:44 AM

Hey everyone.

I've asked about this on two other forums, but I'm stumped at this point so I'm looking for as much info as I can get. This is on my '78 Kawasaki.

Here's the story-

Labor Day weekend, was riding my bike home at the end of a 35-ish mile trip when it started running very poorly. Sounded like it was running on one cylinder, had no power, was crackling from the exhaust when you let off the throttle.

I got it home and decided to go ahead and rebuild the carbs since I had the kits to do it. Finished that, which was fairly straightforward, and reinstalled them on the bike. Well, then it didn't want to start. Found out I had a weak spark on the left cylinder, so I bought a used Dyna coil, 7mm copper core wires, new plugs, and new points, and installed them.

This leads me to where I am now: I can get the bike to start (sometimes), but it runs very rough, and puffs black smoke out of the exhaust while running. Throttle is very slow to respond. It only runs for 30-40 seconds and shuts off, which I think is because it's fouling out the plugs; however if I pull the plugs they are making a good spark even when fouled (and they are BLACK).

Everyone keeps telling me it's the timing, but since I never messed with the timing before all this started happening, I don't know how it's related. I think it's the carbs, but I don't know what to look for. I'm pretty mechanically inclined, I rebuilt the engine in one of my cars and it now has 30K on it, but carbs are pretty foreign to me (been working on fuel injection only so far).

I have a manual on CD for this bike but it hasn't been much help so far in diagnosing this problem.

Any advice, tips, etc?