Loud Vibrating Sound coming for acceleration/engine braking

[quiktaco]

I have this wierd vibrating sound coming from around the engine during acceleration, and especially during engine braking.  If I pull in the clutch, the sound stops.  I don't know if it's from the engine itself or from vibrating caused by the engine.  I really want to figure this out, but I can't track down where it's coming from.  It sounds like something is going to fall apart.  Any ideas?

[quiktaco]

Anyone have any ideas?

[coll0412]

A bearing thats about to go?

Magnet has broke loose on the stator rotor and is making a nasty noise?

Does it do it when its idiling? How about if you rev it in neutral?

[quiktaco]

Don't know about a bearing or magnet.  Could be, but I don't think so.  It doesn't do it at a sitting idle.  It does it slightly in neutral while reving it.  It's a lot more prominent while riding it though.  The main time that I hear it is while engine braking/downshifting.

It started 2 days ago, and today seems worse than yesterday.  I downshifted too much, and foolishly skidded the back tire cause of it.  Nothing seamed to be wrong, and it ran fine after, but the next morning it started doing this noise.  That's the only thing I can think of, that could have caused something to go wrong, but what, I don't know.

[quiktaco]

It's almost like it could be something outside the engine.  I almost thought it was the headlight bucket that was loose and vibrating, but I've gone over the bike 3 times now and can't find a single thing that's loose.  (it sounds like it's farthur down than the headlight bucket...with my helmet on, it was hard to hear exactly where it was).  I also drove with my helmet off in a small residential area to see if I could track it down, but had no luck.

[DarkStarr]

I have the exact same problem, except sometimes I cant reproduce it.  I notice it the most around 4500 RPM's...  I'm about to take it to the dealer and have them look at it, but it hasn't affected any performance that I have noticed.

[GeeP]

Probably the gas tank.  A known problem right around 4,500 RPM.  Fill the tank or grip it really hard with your legs.  The sound should go away.  If so, check the rubber strip that lines the bottom of the tank and the pad that isolates the front catch from the frame. 

[DarkStarr]

I'm about to head out in a half hour, when I get home tonight I'll give a report!  I do notice it less with a full tank too...  interesting.

[The Buddha]

Yea gas tank can vibrate but that is a very low bass drum kinida noise and will be both on the throttle and on trailing throttle.
Trailing throttle noises are typically lower end related, rod bearings, crank bearing etc.
Cool.
Buddha.

[ABSOLUTNATI]

I just fixed something like that yesterday. It was my windscreen. Only needed a quarter turn on the screws to tighten up and made a WORLD of a difference. I also had to tighten my tach cable last year which caused buzzing. Think of something very simple before you go looking for major mechanical issues.

[quiktaco]

AWESOME!  Thanks guys, it was the gas tank!  I guess when I was messing with the carbs a few days ago, I must have knocked off the right side rubber pad thing that keeps it off of the frame.  I rode it this morning to work, and just lifted the right side of the tank with my left hand and it went away.  I was so worried that it was something in the transmission or something.

At least coming from this problem, I don't have a loose nut or bolt anywhere on the bike, oil is topped off, and I found a missing bolt (not super important one) that I replaced.

[The Buddha]

K good, I have run with both of them missing for years, not loud by any means ... atleast not on the 2-3 I have done that on. Cam chain and cam shaft end play noises are far louder.
Cool.
Buddha.

[quiktaco]

My tank is missing the rubber strip that goes around the bottom of the tank edge.  It was metal on metal vibrating, and I could here that noise easily over my engine and exhaust.  It was definitely loud 

[The Buddha]

That rubber thing ... OK none of my bikes have had that. hey, I am not saying your analysis is not right ... just that I never had it sound loud, and I sold 1-2 bikes that way most notably the seca I just sold. However that thing was smooth as butter by the time I was done with it, it could ahve had no bolts in the tank and still made out the same way.
BTW carbs being nice in synch can make it vibrate less ... regardless of what your tank is doing.
Cool.
Buddha.

[quiktaco]

Ok, I'll check to make sure the carbs are in sync, too.  Thanks

[DarkStarr]

I'll just have the dealer look at it when they are checkin out the rest of the bike..  can't seem to find the cause.