Chain Slack, Make/Model Specific???

gthoma23

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Apr 24, 2008
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i'm just wondering if the chain slack is different each make/model?

I went through, took off my shock, made the SC, pivot bolt, and rear axle aligned. Then mearured the distance from sprocket center to sprocket center (which was 25.75") and multiplied that by .02 (2%) which gave me 0.515. So i went i adjusted my chain til it had .51" of total movement (amount able to move up added to the amount able to move down). So after that i put the shock back on. the problem was, my chain was almost the exact same after putting on the shock.

did i do something wrong? or does it matter what make/model you have if this works or not?

and also, my manual says my chain is suppose to have 1-1 3/8" of vertical movement. does that mean just how much the chain is suppose to move up, and not add what it can move down?

thanks...
 

2-Strokes 4-ever

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Hmmm. I believe KTM's are different than most. As a rule of thumb aprox 2 1/2" is usually good. On our past Honda's, Kaw's, Yam's and our current Zuk's we use the 3 finger measure (about 2 1/2".) Just to the rear of the top of the chain slider adjust slack so 3 fingers slide in. If Honda is saying 1-1 3/8 "vertical slack" I betcha' you could push it down an inch or so to come up with the same total. Why does Honda have to word it so differently?
 

Ol'89r

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gthoma23 said:
i'm just wondering if the chain slack is different each make/model?
did i do something wrong? or does it matter what make/model you have if this works or not?
All bikes are different. It depends on the relation/angle of the countershaft sprocket, the swingarm pivot point and the rear axle. If you compress the rear suspension all the way down, you will notice the chain will get tight and then get looser. On some bikes the chain will start out tight and get looser as the suspension compresses. On others it will start out loose and get tighter as the suspension bottoms out. Sometimes it starts out loose and gets tighter in the center of the stroke and then gets loose again. It all depends on if the countershaft sprocket is located in line with the rear axle and the swingarm pivot or is positioned above or below that line.

You don't have to use the formula that Honda gives, just compress the suspension until the chain is at it's tightest point in the stroke and adjust it like 2-strokes said at about 1 1/2 to 2 1/2" total up and down slack at that point.
 

gthoma23

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Apr 24, 2008
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2-Strokes 4-ever said:
Why does Honda have to word it so differently?
good question, some1 needs to re-write these manuals so they make more sense. but i always hear different things about the 3 finger rule. but when u say 3 fingers, is that so ur fingers can slide in w/out touching, or that you can barely fit 3 fingers in?
 
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2-Strokes 4-ever

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We do 3 fingers slide in comfortably.
 

XRpredator

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gthoma23 said:
. . . when u say 3 fingers, is that so ur fingers can slide in w/out touching, or that you can barely fit 3 fingers in?
2-Strokes 4-ever said:
We do 3 fingers slide in comfortably.
must . . . resist . . . :bang:
 

2-Strokes 4-ever

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XRpredator said:
must . . . resist . . . :bang:
Where this gets REALLY creepy is just imagining what the "defininition of marriage" is on Planet Hillbilly... eeewww

(hands over ears)... "La la la la la"
 

Jaybird

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No matter what bike it is, there is a tight point for the chain. This point will also be when the CS, swingarm, and rear shaft are in alignment. Physics and geometry makes this happen, and does not distinguish between bike brands or models.

Accepted engineering practice for a chain drive states that the slack of the chain should be between 1%-3% of the distance from front driver shaft to the rear driven shaft.
Adjust the chain so it has 1% of the distance of your shafts, in total up and down movement of the chain, when it is in it's tightest position in the travel. Then check until you reach 3% and then readjust.

Manuals are confusing and in many cases flat out wrong. Several reasons for this, but if you use standard engineering practice, you cannot go wrong.
If things didn't work out, back up and see what you did wrong.
 

gthoma23

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Apr 24, 2008
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Jaybird said:
Manuals are confusing and in many cases flat out wrong. Several reasons for this, but if you use standard engineering practice, you cannot go wrong.
If things didn't work out, back up and see what you did wrong.
I read ur post on this subject before, and followed it when doing this. my question is, is it possible to not have to point of where it it the tightest not to change throw the stroke of the shock? cause i think i did it right, but it never change the amount of slack between when the CS, swing arm and axle were aligned.
 

Jaybird

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Geometry will not let it happen like that. Especially since you have linkage that connects the swing arm to the frame.

I would go through the procedure again. Make certain that you have the cs swing arm and rear shaft all in a straight plane. You should be able to line a yardstick edge up with the center of each item perfectly. If not, you are not there yet.
Now, putting the swing arm in that position so you can work on it will mean one of two things...you either have to remove the shock, or you have to hold the swing arm in the correct position with a strap of some sort. This should be when the bike is off the ground and on a stand.
My suggestion would be to remove the shock to do this adjustment. It is much easier to adjust correctly this way.

IF you do have the thing in it's tightest position, and it DOES have a tightest position, then you want to have the 1% of the shaft distance in total up and down movement of the chain. When you have it like this, you will find that you cannot make it get any tighter, but you can easily make it looser simply by letting the swing arm go back to where the shock takes it once remounted.

This task is very tedious, and you will need to double and triple check both your tension measurement and your alignment when tightening things back up. This is the point where many make the mistake of not rechecking, and when it is all buttoned back up, it won't be the same as they thought they had it. Things can move very easily when tightening, and we are only talking about very little movement to get things hosed up. So check, and recheck as you tighten things up.

Go through the procedure again and see if you don't find just what I'm telling you.

Also...
Once you do this procedure, the first thing you should do after it's done correctly is to put the bike on the ground in normal ride position, and then see just exactly how much distance there is from the chain to a spot on the swing arm...like the edge of the chain slide, or something stationary. You can then forget about taking the shock of and all, and simply readjust to that measurement from then on.
Now, that measurement when on th4e ground is going to be different when on the stand. So take two measurements. One on the ground, one on the stand.
Use your ground measure so you can keep an eye on your chain at any time you want.
And know what the measurement equivalent is to that while on the stand, because THAT is where you will have to do the adjustment work.

I hope that makes sense to you. If not holler and I can try to be more clear.
 
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