Shake/thumb felt through the footpegs, only in 3rd gear

[Squishy]

Btw, when I tried setting the chain tighter.. the whining got MUCH MUCH worse, and it pretty much every gear.. but I figured it was the chain rubbing against the glider or something..

Now I think about it might have put more strain on the axle or bearing, causing that noise..

[ventYl]

I think you posted the incorrect youtube link ventYl...

Why? It makes exactly that noise at 0:35 

Well, then I think it is time to inspect your gearbox. IIRC It should be accessible after removing oil pan with engine in frame. Wasting one day by gearbox inspection is better than wasting whole bike when something blocks gears while in motion. Gears are still available and the price is not killing.

[Squishy]

I think you posted the incorrect youtube link ventYl...

Why? It makes exactly that noise at 0:35 

Well, then I think it is time to inspect your gearbox. IIRC It should be accessible after removing oil pan with engine in frame. Wasting one day by gearbox inspection is better than wasting whole bike when something blocks gears while in motion. Gears are still available and the price is not killing.

Hm, well on this board someone (Chris H) said you need to remove the flywheel and clutch first?
http://forums.banditalley.net/index.php?topic=13754.msg108953#msg108953

Does someone know exactly what needs to be done?
In the manual the gearbox is the last thing on the list on engine removal..

[ventYl]

-> shop manual

google knows where to get it

[Squishy]

-> shop manual

google knows where to get it

I've got the manual.. but it only says how to dismantle entire engine to get to the gearbox..
Or is there another manual?

[ventYl]

you just need to get a visual contact so check if before removing oil pan there are any additional steps affecting the engine (you have to remove output headers) and also if removing oil pan will get you a visual reach to gearbox.

this should be deducible from pictures in shop manual

[greg737]

VentYl is right, taking the oil pan off gives you a pretty good view up into the gearbox.  I used this method to inspect the gearbox of my fuel injection project bike.

The only drawback is having to look at it upside down from underneath the bike.  I used a combination of items to do my gearbox inspection: I used a mirror for general looking and a USB boroscope hooked up to my computer for the fine detail looking.

I was able to thoroughly inspect every cog and dog in the gearbox.  I wasn't paying close attention to the bearings though so I don't know if they can be viewed easily with the mirror or boroscope. 

[Squishy]

VentYl is right, taking the oil pan off gives you a pretty good view up into the gearbox.  I used this method to inspect the gearbox of my fuel injection project bike.

The only drawback is having to look at it upside down from underneath the bike.  I used a combination of items to do my gearbox inspection: I used a mirror for general looking and a USB boroscope hooked up to my computer for the fine detail looking.

I was able to thoroughly inspect every cog and dog in the gearbox.  I wasn't paying close attention to the bearings though so I don't know if they can be viewed easily with the mirror or boroscope.

So you can just remove the oil pan without removing anything else?
Then what did Chris H mean in the other topic?

[greg737]

Yes, if your intent is to merely inspect/troubleshoot the gearbox then viewing it from the bottom after removing the oil pan is the way to go.

Because I was refurbishing my entire project bike I did this: With the bike up on stands (front and rear to get it up in the air and stabilized so I could put my head under the engine), drained the oil and then removed the oil pan.  Once this prep work was done I began inspecting the gearbox.

I also removed the chain and the countersproket so I could spin the gearbox without the extra noise of the chain clacking across the countersproket.  I used a rubber coupling and a cordless drill to spin the gearbox when I wanted to listen to the gearbox bearings.  A "mechanic's stethoscope" is a nice thing to have/use when you're trying to determine if a bearing is good or bad.

[greg737]

VentYl is right, taking the oil pan off gives you a pretty good view up into the gearbox.  I used this method to inspect the gearbox of my fuel injection project bike.

The only drawback is having to look at it upside down from underneath the bike.  I used a combination of items to do my gearbox inspection: I used a mirror for general looking and a USB boroscope hooked up to my computer for the fine detail looking.

I was able to thoroughly inspect every cog and dog in the gearbox.  I wasn't paying close attention to the bearings though so I don't know if they can be viewed easily with the mirror or boroscope.

So you can just remove the oil pan without removing anything else?
Then what did Chris H mean in the other topic?

Almost forgot... I think you may also need to remove the oil pickup after you remove the oil pan.  I remember doing that too but can't recall whether it was due to gearbox viewing or "just because it was there".  Either way it's easy to remove and replace.

[greg737]

Another "also":  Over the last few days I was reading this thread and giving it some thought.  I was intrigued by your description, that it was noticeable in one gear and not in others.

The only thing I could come up with was this: In a standard 6 speed Constant-Mesh motorcycle gearbox you have two shafts, the "drive" and the "driven".  This entire assembly turns (is carried by) four bearings, one at the end of each shaft.  You would think that if one of those bearings was going to make noise it would do it no matter what gear ratio I engaged. 


But while thinking about your problem I began to wonder if that's not true because when you select different gears the vector of force within the gearbox changes.  There are some good demonstration videos of motorcycle gearboxes that are posted up on YouTube that you can watch to see this.  With every gear change the path of power transfer through the gearbox also changes.  Each of these unique pathways has its own unique vector of force and that vector will affect the four bearings that support the gearbox differently.

This might explain your experience with the sound/vibration/thrumming feeling.

[greg737]

And... Good luck with this problem, we're all pulling for you.

[Squishy]

But while thinking about your problem I began to wonder if that's not true because when you select different gears the vector of force within the gearbox changes.  There are some good demonstration videos of motorcycle gearboxes that are posted up on YouTube that you can watch to see this.  With every gear change the path of power transfer through the gearbox also changes.  Each of these unique pathways has its own unique vector of force and that vector will affect the four bearings that support the gearbox differently.

This might explain your experience with the sound/vibration/thrumming feeling.

Bit of a late reply.. I haven't done anything to the bandit all winter (busy on GPZ900 and GSX600F) .. but this sunday I replaced the oil and filter and went for a spin. There wasn't any hard metal or aluminum on the drain bolt or on the inside of the thread.. so that's good.

The shake/thumb is still there though. I thought about what you said, and I can understand it happening only in one gear by way of unique vector of forces etc.. but do you really think it could be so specific that it can only happen between 4k and 5k rpm.. and not at 3k or 6k rpm? The vector of forces would apply throughout the entire rev-range. Only maybe some specific resonance could explain it but I find it very hard to believe...