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Changing sprocket Q


Mister2

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hey, putting new chain and sprockets on my 00 CBR, i bought a RK kit from local dealer, and my question is this...

i installed the new driving sprocket (quick accel kit) and tightened down the bolt, but the sprocket can move about 1/8 in. in and out on the shaft, is this normal? the old sprocket had a rubber grommet on both sides but its made on the sprocket where as the new one does not,

i just wanted to get an opinion from someone who has done this before. this is my first chain/sprocket swap and i dont want to mess anything up...Thanks for the advice!!!

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ok..well to be sure, i installed the old sprocket and it had movement in and out also, but i am unable to torque the bolt down to spec without the chain on to keep it from turning, so idk if it was all the way tight...

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ok..i will try and explain better, take pics if need be..

the driving sprocket fits over a splined shaft, splined shaft is tight, no play or slop, there is a bolt that fits in the middle of the splined shaft that holds the sprocket in place, with the bolt drawn up agianst the sprocket, there is *about* 1/8 inch of movement of the sprocket on the splined shaft in and out, (toward the bolt and away) i figured it just has this small amount of play so the chain can track straight. but i just wanted to make sure....

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what brand sprocket is it? is there at least a spacer or built in metal grommet on one side? When I changed my front sprocket, the OEM had a metal spacer built in. Although the pictures and logo's showed it should be in one way, it had to be the other way otherwise it would not line up.

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I'm going to guess that the particular original design had a bit of vibration or wear when the front sprocket doesn't have the rubber bushings of the stock front sprocket.

I'm also going to guess that the aftermarket front sprocket will work with the free play, shimmed up with rubber washers, or shimmed up with steel washers. The chain itself has enough flex to handle small misalignment. But if the sprockets wear on the sides of the teeth, the alignment between front and rear sprockets is way off. It's also worth looking for that type of wear on the old sprockets.

Good question. I don't know what I'd do without looking at the two sprockets first. Best guess and quick fix would be to slap a big rubber o-ring on one or both sides and torque it down. Both sides, I think, since the stock sprocket had rubber on both sides.

edit: I'm trying to pin down what the design specs might be, but not having any luck yet. Not even the Honda common service manual.

Edited by ReconRat
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I don't see what's wrong w/ some lateral float? :dunno: You probably want some of that designed in so the front sprocket will end of in a "position of least resistance" relative to the chain and rear sprocket.

The OP said the inner part of the sprocket fits on the splines without play so there's no vertical movement, but I have a feeling the outer will true itself laterally after a run down the road. I'm assuming it can only move laterally in the strictest sense, no yaw or twisting in the sprocket.

Shimming it won't hurt it if you want a "belt and suspenders" approach, but I don't think leaving it float on the spline is going to hurt either.

I'm not a motorcycle tech though and I've never changed my sprockets. :dunno: I'm waiting to see what Tom comes up with as the right answer.

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Mechanical Design Handbook, in the section on transverse vibrations of chains, it indicates that chains have resonate vibrations at critical speeds. In such cases dampening is used.

I would have to guess that any motorcycle using a stock front sprocket that had dampening, would be one that the engineers thought there might be a resonate vibration that needed to be dampened.

So if the new sprocket is installed without dampening, and a bad vibration is noticed that wasn't there before, it would need to be dampened. It would be at a particular road speed, not rpm.

In other words, a chain has a natural bad frequency at which it vibrates too much. That has to be avoided or fixed.

edit: Replicating the alignment of the stock front sprocket is a separate issue.

Edited by ReconRat
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oh hey, very cool... Regina Chain in Italy, a webpage of info on chains and problems. In English, even.

http://www.reginachain.it/eng/use_and_maintenance/how_to07.shtml

http://www.reginachain.it/eng/use_and_maintenance/index.shtml

nothing on sprockets though.

Edited by ReconRat
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well the washers would have to be splined, or very small outer diameter or it would contact the chain...but what is the general thought on this? some play or no play?

Since the washers are not under load there is no need to have splines on them. I had to use them on my klr to space the sprocket out. If the OD is to large grind them down. Only reason Play isn't a okay is that a loose chain could twist the sprocket and bind in the empty space resulting in a total lock up of the rear drive.

I'm surprised no one has come out with a bushing that can be stuck to the inside of a sprocket. Again since it's just a spacer it doesn't have to be attached too securely, just enough to keep it centered during installation.

Edited by buildit
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Since the washers are not under load there is no need to have splines on them. I had to use them on my klr to space the sprocket out. If the OD is to large grind them down. Only reason Play isn't a okay is that a loose chain could twist the sprocket and bind in the empty space resulting in a total lock up of the rear drive.

I'm surprised no one has come out with a bushing that can be stuck to the inside of a sprocket. Again since it's just a spacer it doesn't have to be attached too securely, just enough to keep it centered during installation.

+1. My 520 conversion came with a washer to help w/ the sprocket alignment. It's important to get a straight path from the front to the rear sprocket. Slipping a chain on a moto isn't as forgiving as on a bicycle. :eek:

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