I have a 2007 Triumph Tiger with 15,500 miles on it. Under VERY light throttle above 4,000 rpms, the engine has a stumble to it. Under regular throttle it runs very strong and has no issues, but if I am coasting down a hill at 4500 rpms and barely have the throttle open, the bike will lurch like I have chopped the throttle off and back on. You can see evidence of it in this video:
I thought it was an ignition miss, but a mechanic I showed the video to thinks it is too "smooth" to be a miss, and more of a fueling issue. I believe the previous owner changed the plugs at 12,000 miles. I am just trying to narrow down the problem to see if I should order any parts before I tear into it (I live a ways from a dealer, so I am going to buy off Ebay and then resell the ones I don't need).
I would love to hear opinions from experienced mechanics.