Hello HD forum peeps,

I recently bought a 2008 Crossbones with 6000 miles on. Seemed like a steel at 9k. It was over 100 degrees when I test drove it and all seemed good. Wasn't until the temp dropped that I realized there was a problem. The bike backfires and/or just looses power under hard acceleration. Happens at higher temps just not as bad. No backfire under deceleration and it runs fine as long as I roll on the throttle slowly. The more the temperature drops the worst it gets. At 80 degrees it starts to backfire with every shift. At 70 degrees it is almost unrideable cutting out with anything more than a quarter throttle. Also, doesn't seem to happen unless under load. Can give it quick revs in neutral w/o any problem.

I took it to Harley and they flash tuned it. Told me, "it is running much better now". Paid the bill, got out on the street, hard into the throttle, and it cut out again. Took it back they decided it was the fuel pump. Don't know why since they did a fuel pressure test and it was good but they said they didn't have time and I would have to schedule an appointment. I figured I could throw parts at it a lot cheaper then they could so I replaced the fuel pump, then both fuel lines and check valve, then filter and regulator. No change. Took it to a guy with a dyno who was really sure that the problem was in the tune and he could get it dialed in for me. Got one pull w/o it acting up and that was the end of that. He realized he couldn't tune it because of the cutting out. But I did learn that it was running rich (about 11.5) through the whole rpm range on both cylinders. He decided it had to be the coil. It wasn't. I'm at a loss. Hoping someone out there has dealt with this issue before. Thanks in advance for your help!

For those who don't know 2008 crossbones is fuel injected. Not a carb issue. Only mods are pipes and air filter as far as I know

 

I had very similar symptoms, after much head scratching, carb stripping and cleaning (I know yours is injection) and replacement spark plugs and then coil and leads which temporarily seemed to fix it only to return later...I discovered that a bit of fancy chrome shroud around the coil was just barely touching the HT lead to the front spark plug where it exited the shroud, over time with a bit of vibration it cut into the lead just enough to short it but only under load (hence new leads provided a short term fix). It would run fine as long as I was gentle on the throttle but, open up and it would lose power and pop and stutter.

Have you tried changing the plugs and/or leads and checking for anything touching?

 

Thanks for sharing your experience. I didn't find anything touching though it an electrical problem does seem to make the most since at this point. May be a weak spark under load because of short of some kind. What you found on yours does reinforce that theory. I did swap out the plugs. I checked the leads for damage but didn't find any. I will try swapping them out next.

 

Turned out to be a bad timing sensor. Runs great now

 

First time ever hearing of a timing sensor
glad to hear it worked for you. Love the CB enjoy

 

I'd like to """THANK""" you for letting us know what the fix was..

Many of the other members NEVER post back to let us know if they got their bike fixed or at least us know what was causing the problem..