Topic: Front sprocket wiggle - 750 78K - how much?

[fxef79]

So I know the front sprocket has some “wiggle” to it, both with the “two bolt” attachment method and with the K7/K8 center bolt. But just how much lateral movement is ok?  I just feel like this is a lot. I’ve got a total of 2.3mm of lateral movement.


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[BenelliSEI]

Does lateral movement man the sprocket slides along the shaft that much? As long as the lock plate is firmly engaged in the slot in the shaft, and both bolts are tight, it can’t come off. Should be OK.

[Alan F.]

77&78 don't have 2 bolts or a lock plate, just a single center bolt. I don't know how far toward the cases it can wander though.

[BenelliSEI]

77&78 don't have 2 bolts or a lock plate, just a single center bolt. I don't know how far toward the cases it can wander though.

Totally correct, my mistake (and I have one!).

[Alan F.]

I'd guess it's got a little side to side movement built in by design to keep the front sprocket lined up and lessen the possibility of wear from misalignment.

If you can push the sprocket toward the cases and a 630 chain doesn't touch anything, I'll bet you're ok. Convert to 530 next time you need new ones if you're concerned.

I just picked up a cheap o-ring chain and good quality sprockets for my K8, if I ever wear them out I'll convert to 530 too.

[fxef79]

I'd guess it's got a little side to side movement built in by design to keep the front sprocket lined up and lessen the possibility of wear from misalignment.

If you can push the sprocket toward the cases and a 630 chain doesn't touch anything, I'll bet you're ok. Convert to 530 next time you need new ones if you're concerned.

I just picked up a cheap o-ring chain and good quality sprockets for my K8, if I ever wear them out I'll convert to 530 too.

I should have said this, sorry. It’s already a 530 chain. It doesn’t hit the case.


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[fxef79]

I know that some wiggle is normal, I just don’t know how much. 2mm ok?


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[754]

Loctite the bolt, use the  right  cover, that will stop said bolt from coming out, put together and ride it..

[maxheadflow]

AFAIK, the washer on the K8s is supposed to keep it from wobbling. It's sort of a special spring washer.  Possible you don't have the right one.

[Alan F.]

Not sure about that Max, looks like a fender washer to me, but thicker.

Center hole is for an 8mm bolt.
https://www.cmsnl.com/products/washer8mm_90401405000/

[754]

All KO to K6, had floating sprocket.... can you think of acreason K7 and K8 should not.. washer is flat I think.l

[maxheadflow]

This is not a good picture but the washer is sitting on top of the clip for an earlier sprocket. It's just one of the issues I found with the bike..

Side view it kinda looks like this..     

    )
   |
hole
   |
    )

[fxef79]

This is not a good picture but the washer is sitting on top of the clip for an earlier sprocket. It's just one of the issues I found with the bike..

Side view it kinda looks like this..     

    )
   |
hole
   |
    )

That doesn’t look right.


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[maxheadflow]

OK it's more like this.  The outside edges are such that the washer has some give to it. The give clamps clamps the sprocket against a shoulder on the shaft.

[maxheadflow]

Post a pic of what you got..

[fxef79]

Post a pic of what you got..

Well, here is what was on the K8 when I got it. Note: the extra “spacer” ring you see shouldn’t be there. Doesn’t belong.


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[fxef79]

Post a pic of what you got..

And here is what was on the 73.  Note, the center “bolt” in this case holds nothing on - it is the chain oiler.




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[fxef79]

Post a pic of what you got..

Now, here is the shaft in the 73. Note the slot around its circumference which is for that plate that is held on by the two small bolts. That plate/bolts arrangement will only work on a 76 or earlier, because the 77/78 output shaft doesn’t have it. And the 77/78 doesn’t have a chain oiler - it is the center bolt that holds things on.




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[fxef79]

Post a pic of what you got..

And here is the 78 output shaft. No slot. So your arrangement could only be done on a 76 or earlier. But in that case you should have a chain oiler, not a center bolt or that washer.


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[Alan F.]

630 and 530 links are both 9.53mm wide. The 530 sprocket should have the same side to side motion available that the 630 would have. That extra spacer was probably added to take up the "slop".

[754]

The thinshim ring is probably there, because its a non shouldered sprocket.... stock are... meaning thicker in the middle. Ghe washer I have seen in K7 and K8 have been the big flat one..

[fxef79]

That extra spacer was probably added to take up the "slop".

That's what I think the PO did, when they swapped the sprockets (K8 should be a 630 chain with a 15 front/41 rear, but this had a 530 chain and 17 front sprocket).  So I guess someone put the new sprocket on, bolted it up and said "whoah, that sprocket wiggles.  Well, I'm certain I know better than Honda engineers, I need to add something to tighten up that sprocket... here, this doohickey looks like it'll fit in there". 

Note, that spacer was NOT centered when I took it apart, it was, for obvious reasons (spinning sprocket, nothing to keep it centered) slid off-center.  You can even see the pattern on the picture I showed of the wear mark on the sprocket where the spacer would sling around.

So I know there *should* be "slop"... I just wonder whether there's more here than there should be.

At this point, I'm gonna "send it".

[754]

Like I said stock is fatter in the middle, guess you need a pic or measurement, yeah the  shim  should have smaller id

[maxheadflow]

The problem is that theses bike are all old enough that it's hart to tell what the original was.  I do suspect that the washer I have is correct and that the sprocket base is wider than the sprocket teeth if you have the correct sprocket.  I don't think the sprocket floats on the 77/78.  The washer I have provides a light spring pressure on the sprocket to hold it in place. I've seen the same setup on newer Hondas.  I won't swear for sure tho as the part I have may be off a later bike.. When fit correctly there is a light pressure from flex on the washer holding the sprocket in place and the center bolt bottoms on the end of the shaft.

[754]

Post 11 shows a thicker stock sprocket.