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Click/pop taking off- I'm out of ideas.


shinyribs

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Nearly since the bike was new I would hear an occasional click/pop kind of sound on initial take off. I don't know how to describe the sound, but imagine a grain of sand between the chain and a sprocket tooth. Crunch.

On paddock stands when you put a rag on the chain/sprocket to wedge the rear tire forward for tightening the axle I can recreate the click. Hunting for it by feel is fruitless as I can feel the click pretty much throughout the entire frame. I can see any parts jumping or shifting either. 

I've inspected the front sprocket and how it fits on the countershaft. I've used other front sprockets and no difference.

I replaced the chain with no difference. 

I've inspected the cush drive for grit, but found nothing out of order. Full clean and reinstall with no difference.

I've closely inspected all of the rear wheel bearings/spacers- still perfect at 20k miles.

More than once ( last night included) I've pulled the swingarm and inspected all pivots and mounting points. Wondering if it's a needle clicking in the swingarm pivot. Everything feels tight and visually checks out as undamaged. 

The only thing unexpected that I've found is the color of the grease in the swingarm pivots. The grease I use is red when it's fresh. The grease in the pivot on the brake/exhaust side of the bike never loses its color and will be fresh every year when it gets serviced. The grease on the chain side will be black like it's been beat or contaminated. The seals on that side are still very tight. I can't imagine what could be contaminating it anyway. Chain lube cannot be making it's way in there, and I use kerosene fire cleaning the chain. The small amount of kero that may drip off in that area ( never noticed any) shouldn't be able to seep in to the pivot area. If it could, I don't believe that would turn the grease black anyway. 

Is there strictly enough pressure in that area to beat the grease up that bad? 

 

The swingarm pivot where it interfaces with the needle bearings only show very slight witness marks. Nothing you can feel with a fingernail. Everything is tight and snug still. Just to be sure I made certain to reinstall the pivot 90° rotated to see if something was somehow worn and shifting, but no change. 

As a test I started removing the aluminum side plates that create the outboard supports for the swingarm pivot. My idea was to loosen/remove them one at a time and monitor any changes to look for a clue. The clicking sound never changed from one plate slightly loosened all the way though to both plates completely removed. 

All frame joints have been closely inspected for cracks.

 

I'm out of ideas. 

 

The only thing I can think to do would be replace the swingarm bearings. I absolutely despise changing those little bastards out, especially when there are zero signs of wear or damage. 

 

Any ideas? Anyone else heard this click? 

 

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Is there anything , tools etc, that could be sliding around under the seat on acceleration?

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DewMan
 
Just shut up and ride.

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Hmm. Stumped also, other than changing the bearings in the swingarm. I can tell you from experience changing the bearings in the swingarm isn't that bad at all. I did a full refresh last January, 13 pieces between bearings and seals IIRC. Disassembling everything and raising the rear end and supporting it was the bigger issue I had, I used the step ladder and straps technique.

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3 hours ago, DewMan said:

Is there anything , tools etc, that could be sliding around under the seat on acceleration?

No, but I only say that confidently because I can recreate the sound dependably with a rag in the chain. I'll try to get a video. Who knows, it may help someone down the road.

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3 hours ago, DewMan said:

 

*Site won't let me delete this^

 

Anyway. Sounds much louder here than in person, but it's an accurate sound otherwise. 

 

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Very strange. Could there be a link seized (or partly) in the chain?  Oops, NO you said you changed the chain.

Edited by robbo10
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Just do it! 

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Can you feel various parts while clicking to see if you can feel it at the source.

The rag is tightening the chain. Is that a clue?

Edited by robbo10
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Just do it! 

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That is definitely a noise that would have me concerned.  It sounds like it's coming from counter shaft sprocket area. Is it as loud when you're not using the rag ?  The rag increases the chain tension  and changes the thrust loads. It sounds like you covered all the likely suspects; if it's been doing it for 20k miles and hasn't done any damage yet you may just have to live with it.

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44 minutes ago, bornagainbiker said:

I hate to ask, but could it be coming from the transmission output shaft bearing?

That's kinda what I'm afraid of at the moment. Especially since the bike seems to have a vibration that I don't recall. 

If it's a bad bearing, it's been making the exact same noise for about 18k miles without getting any worse. That gives me some comfort that it's not a bearing issue, but anything is possible.

Currently trying to come up with an idea of how to test this. All I can say definitively for now is the output shaft turns smoothly and quietly with the chain off of it.

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34 minutes ago, robbo10 said:

Can you feel various parts while clicking to see if you can feel it at the source.

The rag is tightening the chain. Is that a clue?

I don't feel any vibration from the click when I put my fingertips on the engine cases. I do feel it when I put my fingertips anywhere on the chassis. I want to say it strongest around the aluminum plate on the chain side, but it's really hard to pinpoint anything. If I remove that plate and perform the test the sound remains exactly the same. 

 

Having that plate off allows the swingarm pivot bolt to flex a huge amount, so I don't really like pushing that, but even when it's making the click sound in that scenario I can't see the pivot bolt jumping to match the click. It just flexes smoothly.

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8 minutes ago, longrider1951 said:

That is definitely a noise that would have me concerned.  It sounds like it's coming from counter shaft sprocket area. Is it as loud when you're not using the rag ?  The rag increases the chain tension  and changes the thrust loads. It sounds like you covered all the likely suspects; if it's been doing it for 20k miles and hasn't done any damage yet you may just have to live with it.

I'm not positive if it's louder with the rag or not. Im usually inside my helmet with the bike running when I hear it taking off, so my perception may not be accurate. 

 

Up on the lift in the video it is definitely louder than usual. I think the sound may be reflecting off the lift table? In everyday circumstances it just sounds like a faint click, like a grit of sand working through the sprocket/chain.

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1 hour ago, shinyribs said:

Up on the lift in the video it is definitely louder than usual.

Jeez,that's a head scratcher for sure. Strange, I'll be checking back to see how this unfolds for sure. 

Good Luck.

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I'm not right in the head just now BUT, my gut tells me to feel around on the suspension pieces, in particular the shock and shock spring. Bear with me for a second. When you run a rag in there like that it loads the entire rear of the bike (the unsprung stuff in particular) That action can cause the swingarm to move which in turn moves the linkages and shock back and forth. That noise almost sounds like the collective slop (technical term for play) in the entire moving rear system popping into and out of tension. All the loose parts such as wheel spacers, brake carriers, brake torque arms, axles, nuts, washers, shims, bearings, bearing pivots, linkage bits, blah, blah all react to said torsional loads in some way.  That type of load, being artificially created in that fashion, would exaggerate the amount and volume of said noise over the same noise being created under normal operating conditions, tooteling down the road. 

Meh?

 

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58 minutes ago, mossrider said:

I'm not right in the head just now BUT, my gut tells me to feel around on the suspension pieces, in particular the shock and shock spring. Bear with me for a second. When you run a rag in there like that it loads the entire rear of the bike (the unsprung stuff in particular) That action can cause the swingarm to move which in turn moves the linkages and shock back and forth. That noise almost sounds like the collective slop (technical term for play) in the entire moving rear system popping into and out of tension. All the loose parts such as wheel spacers, brake carriers, brake torque arms, axles, nuts, washers, shims, bearings, bearing pivots, linkage bits, blah, blah all react to said torsional loads in some way.  That type of load, being artificially created in that fashion, would exaggerate the amount and volume of said noise over the same noise being created under normal operating conditions, tooteling down the road. 

Meh?

 

It is a kinda brutal way to load things, but I'm not pulling on the tire extremely hard to cause the issue. I mean, is not like the sprocket is piercing the rag or anything. But you're right, you can see the bike squat when you load it this way. 

 

As a quick test I'll pop the stock shock back on and see if makes the same noise. I've had the rest of the rear suspension off just last night. 

Hmm...come to think if it, I've been thinking this sound started around 2k miles, and that's about the same time I put the CBR shock on...

Edited by shinyribs
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Just now, shinyribs said:

It is a kinda brutal way to load things, but I'm not pulling on the tire extremely hard to cause the issue. I mean, is not like the sprocket is piercing the rag or anything. But you're right, you can see the bike squat when you load it this way. 

 

As a quick test I'll pop the stock shock back on and see if makes the same noise. I've had the rear of the rear suspension off just last night. 

Hmm...come to think if it, I've been thinking this sounds started around 2k miles, and that's about the same time I put the CBR shock on...

I've heard similar gronks outta my rear end fiddling with it and I can feel it with my hand when I hold the spring, "click-clonk" , viscerally it feels like a collective mashup.

Re-listening to that with half a mind it sounds like your shock spring binding and unbinding in its collars. 

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On 9/25/2020 at 4:44 PM, seven said:

What happens if you put the bike into a gear and do both the test with and without the rag?

The same sound happens. The rag is just a way for me to put tension on the driveline to simulate the forces of accelerating away from a standstill. The noise is the same if I take off in first or second gear, and it's the same using the rag with the gearbox in neutral. 

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  • 2 months later...

See the original post.  The chain does not appear to be the source of problem, replacing made no difference.

On 9/23/2020 at 5:50 AM, shinyribs said:

...I replaced the chain with no difference. 

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DewMan idea use mechanics stethoscope, I know a lifelong bike wrencher who seems to be able to zero in with that easily.

A stupid trick, unscrew the oil filler cap and put your ear close, crankcase has a way of amplifing internal sounds. If you can just get a clue where it's louder/different sounding...

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