I just started riding my 01 Classic a couple days ago and I am getting backfiring from the carb while cruising in 4th and 5th gear. I work as a fleet mechanic at a school transportation facility andhave some experience with mc engines.When it starts to backfire I pulled the choke a little and she cleans right up and starts pulling again. Tonight I was going to pull the carb and clean it and my son was onthe other side of the bike and spot's a vacuum line with a screw blocking it off tucked above the fuel valve.I pulled the screw out and started the bike and the line has pulsing vacuum.

It has a rubber elbow onthe end ( this is where the screw is stuck in ) and for the life of me , I can't find where it goes , although it look's like it should go on fuel valve. I am wondering if this creative repair work may have someting to do with my fuel starvation problem ? Any of you guys familiar with this particular vacuum line ? The line appears to run back over to the carb.

Thanks in advance for allhelp !! Kevin

 

Does your bike have the stock petcock on it? I'm assuming you bought the bike used, and that the previous owner changed out the original vacuum operated petcock for a standard type. The vacuum line would have attached to the petcock to turn on the fuel when the bike is running.

Anyway, since the vacuum line is still attached to the carb, it's probably leaking, letting your carb suck extra air into the intake. Try finding where the line attaches to the carb, remove it, and cap off the fitting. See if that solves your problem.

 

Yep , bought it used last Saturday , the petcock is a standard design off/on/reserve. I will pull the carb tomorrow.Thanks for the help , did not know they had a vacuum operated valve originally.The bike only has 5300 original miles , suffers from not being ridden enough more than anything , LOL

 

The vacuum line attaches to the top of the carb on the engine side- you may be able to access it buy just removing the rear tank mount bolt, loosening the front and lifting the tank slightly. Easier than removing the carb. If you're going to pull the carb anyway, you might as well pull the float bowl and make sure the jets aren't clogged and that the float height is correct. That would also cause the bike to run lean.