Yamaha FJ1200 Carb Spitting

This engine was hard to start and ran poorly before I cleaned the carburetors. Now it starts and idles ok but it spits back through the carbs when running above idle. The problem is most obvious on two of the four cylinders. I haven’t driven it on the road so I don’t know how it runs under load or at highway speeds.

My problem is that I don’t understand the spitting problem. It is more likely a carb problem or could the valves need adjustment? Can ignition problems cause carb spitting?

I’ve never worked on an engine with multiple carbs before. Could the spitting be caused by incorrectly balanced carb adjustments?

Any thoughts/comments are appreciated.

Thanks!

If you haven’t adjusted the valves in a while I would recommend doing that anyway. It’s far better to check and adjust them now then the spend more time on the carbs only to realize the valves were way out of whack the whole time.

Coughing like you describe can be a cause of poor valve adjustment or poor carburation. It often takes a couple trys to get the carbs completely clean and adjusted. If you have a couple floats that are adjusted improperly it could flood those cylinders causing them to cough a sputter like you describe.

If it were me, I would probably just take it out onto the street and run it a mile or two and see how it goes. Then adjust the valves for good measure, then go back to the carbs. The carbs are likely your culprit.

Timing is a consideration, but I doubt it’s the cause. Your bike has an electric ignition.