Motorcycle Repair: Black smoke, Running rich

Question
I have a 99 1500 Kawi Nomad. Getting black smoke out the rear cylinder exhaust. I'm told it smells like gas which makes sense for black smoke. I have a Thunder after market intake. How can the front and rear be different with a single carb/intake?

Answer
Hey GreenNad,The black smoke is fuel for sure.What I don't know is if the rich condition started right after your aftermarket intake was installed.If so it could be the problem.If not than first I would check to make sure your oil level isn't to high and smell the oil to see if fuel has made its way into your bottom end.If fuel is present then your needle valve isn't sealing.Even if there is no fuel in bottom end you might still have trash under your needle valve.The excess fuel tends to be attracted to the rear cylinder,cause its the path of least resistance.Your choke not fully closing can also be a problem but typically both cylinders will be running rich.The only other thing could be incorrect jetting.(if you have had a jet kit recently installed).The best way to clean the needle valve seat is to remove carb,then bowl,and then float.I take Q tips with semichrome polish on them and insert it into the seat and spin it.Do this a few times changing Q tip often.Then spray carb cleaner to remove polish,let dry then insert a clean Q tip to make it shine.On the needle valve make sure there is no debris or crust on the rubber tip,if so then gently remove with brass wire brush or you can just use your finger nail.I hope this helps.David