Chain Slack on S2

[Devic]

Got a question for any S2 owners or anyone that knows the answer.

Every bike I have ever owned chain slack has been 25/30mm so checked my 07 plate S2 the other day in case it needed adjusting and seemed a little slack.

I don't have the manual for it so downloaded them from the Yamaha site, problem is there is the basic one that should come with the bike and then two for the S2 that are more like a full Haynes type.

Looking through them says chain slack should be between 45/55mm which I thought seemed a little bit excessive at 2 inches, after that came the next problem. One S2 manual shows checking the slack up near the front under where the rubber is mounted on the bottom of the swinging arm and the other one shows to check midway along the chain which I have always done with the exception of an Aprilia that I owned.

So basically any 07 or S2 owners/anyone with knowledge on the subject point me in the right direction as Yamaha seems to be arguing with itself in the manuals and doing a search didn't help much either that ranged from 25/55mm.

Thought I would ask as I just read Deefers reply on someone's main bearing 

[ChristoT]

Correct me if I'm wrong, but could it mean 25/30mm at the front rubber, and 45/55mm in the middle as the same thing?

But I agree, that does seem a lot.

[JC]

I don't take much notice of what the manuals say for chain slack, just about 1 inch, when sat on the bike.

[Grahamm]

So basically any 07 or S2 owners/anyone with knowledge on the subject point me in the right direction as Yamaha seems to be arguing with itself in the manuals and doing a search didn't help much either that ranged from 25/55mm.

I've got the FZ6-S (04-06) but the figures are the same, ie 45/55mm measured just back of where the rear shock mounts on the swingarm.

[JoeRock]

By any chance are you supposed to do chain slack with the bike on the centre stand? If so, that's about right 45ish mm of slack on a centre stand will be about 25/30 on the side stand

[Grahamm]

By any chance are you supposed to do chain slack with the bike on the centre stand?

According to Yamaha it makes no difference, you can check it either on the side stand or on the centre stand with the rear wheel off the ground.

[Devic]

Thanks for all the replies, I normally do the chain on the centre stand then check the slack with it off the stand and sat on it or get someone to sit on it while I get down and check.

Like it's been mentioned does seem a little excessive, it's a chain not a whip and like it was mentioned one manual downloaded from Yamaha shows mid point, other shows where Grahamm said near where the rear shock is.

At the moment it's between 25/30mm bit more in some places as got a couple of tight spots so that's where I adjusted from but like ChristoT said does seem a lot and most of the bike dealers I know and asked have questioned it and said normally they adjust to around 25/30mm.

Thanks for all the input though put my mind at rest a bit as I have never in 31 years of riding on the road had a bike that had the chain adjusted to over 2 inches slack 

[chaz]

There might be a formula to work out how much slack you should have? it would depend on the position of the gearbox sprocket to the pivot point of the swingarm the length of the arm the amount of arc it moves etc. this is why there are different amounts.

[ChristoT]

There might be a formula to work out how much slack you should have? it would depend on the position of the gearbox sprocket to the pivot point of the swingarm the length of the arm the amount of arc it moves etc. this is why there are different amounts.

You're right, I personally have always measured my maximum slack

Your comment about a formula made me think. So I gave it a go, and came up with the following algebraic fomula:

Let's call the mass of the rider (in kg - a factor for measuring the chain tension): M
The tension of the chain (in newtons) at the middle point: T
The distance between sprockets (Note! in m, not cm): X
Pivot actuation (pivot to front sprocket): P
As this could vary from bike to bike:
Radius of front sprocket: F
Radius of rear sprocket: R


So, let's see..

Length of chain (taught) would be the following:

Details Chain slack maths L

Chain slack maths L

We need to bear in mind chain stretch (C), so we add the following:

Details Chain slack maths C

Chain slack maths C

The tension is defined by the following:

Details Chain slack maths T

Chain slack maths T

Our slack is now defined by θ, which gives us the following:

Details Chain slack maths

Chain slack maths

And because multiplication is commutative, we get:

Details Chain slack maths 2

Chain slack maths 2

 

Please note, I take no responsibility for the consequences of anyone daft enough applying that equation to his or her bike! 
 

[chaz]

M has increased because of too many Pi's

[ChristoT]

M has increased because of too many Pi's

I was tempted to add a B variable (whatever you had for Breakfast!), but thought that wad going too far!

[acid drop]

So basically any 07 or S2 owners/anyone with knowledge on the subject point me in the right direction as Yamaha seems to be arguing with itself in the manuals and doing a search didn't help much either that ranged from 25/55mm.

I've got the FZ6-S (04-06) but the figures are the same, ie 45/55mm measured just back of where the rear shock mounts on the swingarm.

             07 onwards 45/55mm  same measurements with bike on center stand as quoted in the owners manwell.

[Devic]

Well glad that is clearer now and the last post is back to what Yamaha manuals say although the two S2 manuals still don't agree on where the slack should be measured, apart from that the pages are identical 

[foxbass]

I have read on other forums that the Fazer works best with max spec slack. I have tried mine tighter but this is not a good idea if you ever take a pillion as the suspension geometry means that the chain could go tight. Ditto the effects of rough roads/potholes.

The best advice I received, and has indeed worked well for my last 3 fazers, is : take a screw driver or spanner and roughly mid-way between sprockets, lift the chain. It should easily touch the underside of the swingarm, only going tight just as it reaches.
This amount keeps chain/sprocket wear to a minimum and makes selection of 1st less clunky.

Hope this helps

[Devic]

Thanks for that Foxbass, actually checked the chain again on Thursday as had a couple of long trips last couple of days and thinking probably time for a new chain anyway as this one seems to have been a big naff that the previous owner put on it decent quality chain and probably few thousand miles left in it but it's got about 6 tight spots so a pain in the rear to adjust.