I posted this in the Dyna forum with no replies, so I figured I'd try it here...updated a few bits of info from the last post...
Hey guys,
Here's one for ya. I have an 08 Street Bob with 15K miles on it. I recently started feeling an odd oscillating vibration in 4th gear between roughly 52mph and 58mph. I checked all other gears at topped out speeds for each gear and everything felt smooth. As soon as I shift into 5th gear, maintaining the same speed, the vibration goes away.

Here's what I mean by oscillating vibration... It's not a continuous vibration (like when something is loose), it sort of cycles a little faster than twice per second (was counting in my head while riding). Kind of a "zzz - zzz" thing. I brought it to the dealer where I bought it and they couldn't get the symptom. It seemed like it went away for a ride or two, but now it's back.

My inclination is that it's not an RPM thing, or it would likely do it at that RPM in every gear. The Harley counter guy half assed something about maybe a bent shaft or something, while telling me they could tear down and inspect for a minimum of $400 if I wanted. Not the most compelling sale...you don't have a clue, but you'll investigate randomly on my dime? Anyhow, seems to me like if the drive shaft was bent, it would pose a vibration problem in every gear. I read several posts about vibrations possibly being linked to a tuning issue...I had the bike Dyno'd with a SERT and Thunderheader, seems to run fine...can a Dyno tune get "off"? Does it ever need to be checked or redone? I'd be surprised if it's a tuning thing given that it only happens in 4th gear, but who knows? Just throwing out things I've heard...

So, any input, is my reasoning correct? My gut tells me something is maybe funky with whatever parts are unique to 4th gear...

Any input, advice, help would be awesome and very appreciated. I'm going to bring it to a different dealer (the place where I've been going, where I bought the bike, has a track record of not fixing things to my satisfaction, so I'm done with them) to have one of their mechanics test ride it, but figured I'd check with you all here as well...maybe someone's had a similar problem? I did a search on the forum and didn't find anything like my problem...just more consistent, vibrating all the time issues...

This has, of course, cropped up just as my factory warranty is about to expire. I have no intention of buying Harley's extended "fear" warranty that they want a small fortune for, only to have the dealer or Harley deny that something is covered under the warranty (it's already happened to me within my 2 year warranty). So yeah, I 'd love to figure this out before my warranty expires in just over 2 weeks, ha!

Thanks,
Rob

 

Nothing? At all? No mechanics on this forum? Oh well.