chain slack confusion
 

why it is that on my XTR-09:
-when I set the slack to 35mm: less vibration, smoother throttle control & pick up

- when I set it to 45~50 mm: a lot of vibes, throttle less smooth and pick up from 40~45 mph in top is horrible???????

When I got the bike (new) I noticed the chain slack was around 30 mm, I changed it to around 50. Now 2000 miles later, I decided to make it tighter than the 40~50 spec in the handbook & I got the above result.

I agree I run my chain tighter for less drive line shunt. It's a big single that's what they do.

thanks
great to know of your similar experience.
I am inclined to reset the slack tighter again, the pick up & roll off are so much smoother. I guess less vibes & shunting can only be good.
What's interesting is that the bike when new was delivered with a tighter than handbook chain.

I also noticed a 5 mm increase chain slack between the bike on paddock and side stand which is as I expected

Not that surprising. At the 6k service Tamworth Yamaha wound mine up so tight it was singing on the way home. Idiots. I wound a full turn off the adjusters when I got home.

If you're going to go tighter than recommended, make sure you check there's still a bit of slack through the entire suspension travel. I don't know about the XTR, but if the Ten is less than ~50mm on the sidestand, it goes tight with my weight pushing down on the pillion seat.

I just deal with the driveline shunt.

Although I noticed that tighter means smoother ride, my chain is on the loose side. I've heard and read many times that too tight means extra worn out on the axle/shaft (the thing with sprocket that goes into your gearbox).

@Kev: don't you think that tight is a risk for the axle?

Speaking from personal experience I'd definitely leave it on the loose side. Too tight and you risk trashing the gearbox output shaft bearing - and that means complete engine strip down. Happened to me once on my Africa Twin.

You never run your chain tight so there is no free play, there must be chain slack when the suspension is fully compressed, otherwise you will damags your gearbox.

I adjust mine on the tight side of the Yamaha spec, not tight so there is no free play.

And even tighter fully loaded with luggage and pillion. When going on long trips I get my wife (should use two of her as she is almost half my weight) to sit on the bike with luggage on and then adjust the chain at the tightest point.

OK I put pen to paper (PC application actually) & drew the swing arms/ chain movement and positions for normal & loaded positions (6deg compression).
What I actually saw was that when the whell is pushed up, the front to rear sprocket distance is actually marginally reduced!!
So this means that contrary to what we say, there should be an increase in chain slack??
Unfortunately I can't see a way of uploading the drawing to find out where I've gone wrong. Shame!

I called my dealer & talked about this, they said they tend to set the slack to somewhere between 30~35mm when they do the PDI. So this is what I'm gone a do:icon_pirat: http://www.xt660.com/g:%5Cchain%20slack%20V2.pdf

barking up the wrong tree!!
 

just an quick update after my last post which was contradicting my own previous thoughts.
I got another person to sit on the bike and checked the chain: less slack.
Checking the swingarm linkage, I noticed there was additional pivoting arms which added another plane of movement to the rear wheel as the suspension travels up & down.

So the chain becomes tighter as the suspension is compressed