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Discussion Starter · #1 ·
I am trying to get my 80 Cm400 on the road and I lubbed the chain so I can roll it around before I install a new chain...

While I was spinning the tire I noticed the Rear Sprocket cover that has bolts is moving up and down and I can push on toward the wheel and there is a good amount of play and not sure what it is...

What r the fixes to this problem or is it Normal???? Are there rubber bushings in there that may have dried up and rotted????
 

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Yep, according to the fiche on BikeBandit website http://www.bikebandit.com/houseofmotorc ... 0t/o/m2129 your bike's rear sprocket is held on by bolts that fit into a series of rubber bushings inserted in the drive hub of the wheel. Those bushings can indeed harden/shrink and allow excess play.

They are easy to replace or they can easily be shimmed with a home-made rubber or plastic shim. This will take out much of the play. That said, I don't think there's supposed to be a lot of side-to-side play at all. That is, there's a circlip that holds the assembly in, and again, there isn't really meant to be a lot (if any) side-to-side play.

Take it apart and have a look...

Kirk
 

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Discussion Starter · #3 ·
I saw the rubber bushings in the Service Manual here on the forum....I will have to order a new set of them.
 

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If the rubber cushions are worn or deteriorated it could account for some rotational play. If you can move the edge of the sprocket in and out, like a loose bearing on a shaft, there's something more serious wrong.

I'd suggest taking the wheel off (sounds like you're on your way there anyway) to see what you have.
 

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Discussion Starter · #5 ·
JT...

I am taking the wheels off soon...MY tires are on a UPS truck today...So i am going to be doing this sometime this week...

My life just got busier because I just and another Healthy Child.....Baby Girl Gabriella...

Sorry off subject just so excited....

Hopefully in between bottle feedings I can get this bike rolling..
 

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Discussion Starter · #8 ·
WOW...long time away....Sucks being busy.....

Well I have removed the rear wheel and removed sprocket.....In the mean time I have ordered new rubber bushings and collars....

Upon waiting for goods to arrive I discovered whom ever owned bike previously had no idea on how to fix anything....When the person but all spacers/washers back into wheel underneath sprocket...They installed the Flat washer on Top of Beveled spacer the sprocket slides onto...

The sprocket was resting on a flat washer instead of resting on the beveled spacer....This is why I had excessive sid to side play.....WOW ans someone rode this bike like this because the outer lip of sprocket is marked up from the chain riding on it...It looks like the chain was traveling on this edge close to flying off sprocket totally..

Wow is all I have to say!!!!!

I have put it back together and I am currently riding it....O yeah the rubber bushings also made a huge difference..

Thanks all
 

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You have to love PO's and their 'fixes'. I found so many things done wrong on my CB400T it was scary. Glad you found the issue. Be sure to check out the rest of the bike for these type of things, never know what the PO was up to, don't want something dangerous there just waiting for the right moment.
 

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This is tangentially related. And I'm running into a problem. I'm also working on the rear wheel sprocket. I have a CB400t which has essentially the same set up. I got 37t sprocket and I'm trying to replace the current one. However, when I have the sprocket off of the wheel, it seems to be mounted onto a plate ( see attached diagram ). Should I try and remove the sprocket from the plate or is it a component that I should have ordered that's one piece?

Any ideas will be helpful.

Thanks!
 

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Sensei
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That outer chain guide is not essential for correct operation....
 

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If your chain will lift far enough to clear the sprocket teeth (that extra 1/4" of side guard tin won't retain it anyway), and SOMEONE hasn't been doing proper maintenance.... If you get on ANY bike to ride it without having (recently) checked fuel and oil level, tires, brake function and chain adjustment (at a minimum) you shouldn't be riding it.... I check all that plus the lights at least every few riding days or at set mileages, unless I have just attended to it. (F.Ex , just fueled up, so don't need to check that today...)
 

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Attached is a photograph of the sprocket that's identical to mine. Ignore the rust. The thing that concerns me is that chain guard has a metal lip which gives the sprocket an additional 1/2 inch where it's not resting against the hub. It doesn't need this?
 

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Sensei
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I don't understand your question.... The sprocket center hole "rests' around/against the hub (touches it) and the "pins' transfer the rotational force to the hub (usually through rubber cushions)... The washer and circlip retain it on the hub...... You could drill out the four rivets and remove the guide, (that "tin" ring around the outer edge near the teeth) as it has no real effect on sprocket spacing....It does not even go near the center hole..... Please refer to this CM 400 sprocket drawing from CMSNL.....( http://images.cmsnl.com/img/partslists/ ... 1_00a3.gif ) as it shows what I'm trying to say...

Are you saying the center "spacer" (very rusty in your pic) is a part of the guide on your bike?... It should be part of the sprocket....
 

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So the new sprocket ( see picture below ) doesn't have that rusty middle ring. Should I try to hammer out the old ring? Does it even come off?


Thanks again for your feedback on this.
 

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Sensei
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Is the inner diameter of the new sprocket the SAME as the inner of the "rusty part"? (is there room to install that rusty spacer assuming it can come out?)
 

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To remove the rusty centre spacer I would heat up the chain ring and then hit it with an ally drift. You could try and quench the middle spacer with a wet rag, this should cause a contraction of the ring and make it even easier to slip out.
Putting it intp the new chainring.
Freeze the middle ring (or if you are in the south UK at the moment) just leave it in the snow :eek: (we dont often get it here so its always a suprise and complete chaos ensues)
Then heat the chain ring in the oven (best to wait till the wife has gon shopping for this part) tap it into position.
 

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Do what Steve says, measure it.
There's a good possibility the maker of the new one compensated for that ring.......it serves no function that I can perceive.
 
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