Chain Slack - what is best?

Notice how both of those ranges cover the 25-30 mm range. Then note that that range is precisely what I recommended in my earlier post. It's important to remember that engineers do not write service manuals, and in fact, rarely even proof read them. We have mark ups with incorrect data in each and every service manual we have on the shelves. This covers Yamaha, Honda, Buell, Triumph, and KTM. They all have issues.

But back on topic, within this bike's rear wheel's range of travel, there will be more chain slack when the rear wheel is hanging (unsupported, as if there were a center stand). As the suspension compresses and the axle moves into alignment with the countershaft AND swingarm pivot, the chain slack will decrease. Keep compressing past that point and the chain slack will increase again.

The rear suspension is loaded more on a rear stand than a side stand, therefore the axle is closer to the tightest chain condition.

Now anyway, the numbers I provided were determined NOT by the manual, but rather by experimentation. We remove the spring on the shock and run the rear suspension through it's full range of motion. This is the only way to collect data on the rear suspension's lever ratio. While we do this, we also check for proper chain tension. At it's tightest condition, we add enough slack and then record what that correlates to on the paddock stand. Back to the 25-30 mm number...which again, is what Yamaha recommends.

I must admit that I realized I had a brain fart after I saw your response.  You are right.  But even on a stand that supports the swingarm I'm quite sure that both of my bikes have significantly more slack on the "paddock" stand.  I'm traveling and don't have time to check my theory though.  But I do want to apologize in that my response was lacking the logic that I used.  My bad.  Old age setting in.  That's my story and I'm sticking to it!  

It's all good!

It really comes down to suspension geometry. In this case, primarily the swing arm angle. A lot of cruisers have a 'negative' swing arm angle for that "really cool (but useless) slammed look". In other words, the axle is located HIGHER than the swing arm pivot! Any properly designed bike will have a positive swing arm angle to provide some degree of anti-squat. Anti squat is critical in ensuring that the shock operates in the right part of its stroke under all conditions. The chain tension will pull the wheel down with a positive swing arm angle, and conversely, up with a negative angle. With reason, down = good and up = bad.

I'm going to predicate my earlier responses on the fact that every bike is different. While what I said is true of the -10 (and most other bikes), there are other considerations. For example, if the swing arm were allowed to droop far enough, the chain would start to 'wrap' around the swing arm pivot, thus tightening. Same with up travel. HOWEVER, this is highly unlikely in any scenario because good design prevents such a condition. It's also an extreme. Dirt bikes have a tremendous amount of wheel travel (most are 2.25-2.75 times the -10), so the chain tension can start getting funky.

Here's another good explanation with visuals (everything except the bit about the alignment marks...good enough for a dirt bike, but NOT a street/track bike!):

www.motosport.com/blog/how-to-tighten-your-dirt-bike-chain

Got a new video? I can't tell with the last one...

So, I also feel that my FZ is noisy — both at the drive chain, and on the top end of the motor.

My drive chain seems to be perfectly adjusted, though. Slack is exactly what it should be, every way I measure it. Visual inspection says that the chain tracks perfectly centered on the rear sprocket. Finally, I took the time to check rear wheel alignment a couple weeks ago, using the "string method", and it is perfectly aligned. So, I am trying to be at peace with the idea that it’s just how it is. It is my first road bike with a chain. Prior bikes have had drive belts, which are remarkably quiet and easy to maintain.

My top end ticks and clicks exactly as yours does in your video, and I don’t like it. They could be twins. It seems/sounds wrong to me. I took it to the dealership recently to ask their tech to look/listen with me, feeling pretty certain that they would agree that it sounded wrong. I described the noise as a prominent ticking that happens pretty consistently, and is very easy to hear in gears 2, 3, and 4, at RPMs between 3k and 4K, when the motor is running fast enough to make the noise, but we’re not moving so fast that all sound is drowned out by wind noise and such. 

Well, they listened to it and rode it and returned it to me saying that it is running exactly as it is supposed to. My FZ is tip-top, it turns out, and the acknowledged ticking and clicking is completely normal — it’s simply the sound that this motor makes. Then they charged me $125 for that "service", despite the fact that I’ve had the bike only two months, and put only 2,500 miles on it. On the invoice, they did add a list of things that they supposedly checked — I think to suggest that they at least lubed up a bit for me. Evidently, that’s just the "yamatick", as others have described it. The tech tried to describe it to me — why it does what it does. He even suggested that if I wanted a smooth, quiet, purring engine, I should have bought a Honda. Haha!! I still don’t like it, though. 

Anyway, I’m going to install a manual cam chain tensioner, as so many others have done, and seem to be pleased. 

If that that doesn’t work, I’m just gonna install a louder exhaust and ride the sh!t out of it. 

So...what did the dealer tell you? If they replaced the auto cam chain tensioner, they evidently agreed that it didn’t sound right? What do they say now, that it still makes the same noise?

The comment on the fuel is an interesting one. Are you hearing detonation (knock)? If your standard brand and octane isn't working, you may need to find a better supplier. Not all fuel is considered equal (at least here in the states).

What kind of oil are you using in the engine? Another one of those 'not all oils are equals'...but for fear of turning this into an oil thread, I'll stop there.

Yamalube 15w50 is pretty good for hot temps, so that's probably a solid change. It's a long shot, but I'd start playing with the fuels you're using to see if the brands and octane ratings have a repeatable effect.

Octane rating is one of the more straight forward parts of fuel ratings. But there's a whole lot else in the fuel that matters...the cleansers and additives. Here in the states, we have a wide variety of fuels. Our octane ratings are different an just about everyone else in the world, but we can find anything from 85 to 93 readily...with higher on the fringe. Same with ethanol content. But the bottom line is that some fuels just suck.

The good news, is that its easily to isolate if fuel is causing the performance issue. Keep good notes and vary the supply. Most motorcycles do not have knock sensors like our four-wheeled brethren do, so the ECU cannot automatically pull timing when knock starts to occur. Fuel quality matters!

Bikes gone in for a tighten as new chain was installed 600km’s ago.

Different dealership this time and it’s sitting at 2cm as opposed to 5cm by the dealership that’s replaced the cam tensioner and chain.

Bike sounds much better. Still got something not right but better than b4.

Checked new bikes on the floor and all sitting around 2cm of slack.

So much tighter than the other dealerships settings for my chain but spec is 2-3 and given the better ride it produces...obviously the spec exists for a reason.

Which is what I’ve been telling the other Yama dealers all along. Falls on deaf ears tho...