I have a Denim Black 2009 Street Bob and for the past month or so I have been searching for a solution to a problem. The problem that I am seeing is that when it is hot outside, when running, idling or on the road, it sounds like it starts running on one cylinder or that it isn't getting a consistent spark. I open up the gas cap and then replace it and the problem goes away. I have changed plugs and plug wires. Does anyone else see this issue or one like it and have any ideas as to what could be the cause of the problem?

 

I've had this problem recently but haven't figured it out yet. Working with my closed loop bias thinking that the engine was running a little too lean when hot. I'll catch back up if I find anything though.

 

If you are opening the cap and replacing and the bike runs again. Sounds like the vent in the gas cap might be blocked and creating a vacuum in the tank that restricts the fuel pump operation.

 

100% correct vapour lock cap not venting properly

 

Thanks, guys. I'll check that out.

 

Thanks for the responses guys, I too will be checking this out.

 

As an update to the issue that I was having, after much troubleshooting, I found out that the high pressure switch in the fuel tank was causing the issue. Replaced it and haven't had the problem again.

 

Mine ended up being a bad O2 sensor. I took it out of closed loop operation by lowering my AFRs and the issue is gone.

 

How did you determine the problem?

 

Mine (2008 FXDC 13000 miles) has done this twice recently at highway speeds (60-70). I pulled in the clutch and revved the engine and it cleared up. I wish I knew how to determine what was/is wrong. I had a Power Commander and Auto Tuner installed when new by an independent who has since passed away...I know nothing past points, condenser, and carburetor days.