Chain obsession...

[HelmetHair]

The more I think about this, the more I realise the whole problem is not the chain tension as such, but rather the distance the rear wheel can move through its arc.
on sports bikes, with hard suspension, any difference in length created by the swing arm not centering on the front sprocket is minimal.
@ allow a much greater difference to occur, which means getting the chain set up correctly depends on the suspension settings.
if you max the preload (ie jack up the back end on the spring/compress the spring to max) the rear wheel can move only a little bit up and down. therefore, the chain tension will vary only a little bit.
if there is no preload, the rear wheel can move through a huge arc, and create a large difference in the chain tension from tight to loose.

the settings on ATIC and 70mm and @ manual/35-40mm are all very interesting, but if the suspension is not set up correctly for the weight used on the bike (ie rider only, rider and passenger and luggage)AND bearing in mind how worn the spring is, the chain will be either too tight (bad), or too loose(a matter of degree).
the only way to get it right is to load up the bike with the weight you will be riding with, and set the chain tension to its tightest (WITHOUT screwing up the output shaft)
then unload the bike and put it on the centre stand(or lift it with a jack/whatever) and see how far the chain sags. If it can come off the rear sprocket because of side to side movement you will need to increase the preload.
It is then time to reset the max tension again, as adjusting the preload will affect the chain, and repeat until you reach a happy end point.

How loose a chain you are prepared to ride with is up to you, as is how hard a ride you can take-min preload will give a sloppy bouncy ride, max preload will lift the seat up, and you will feel every bump.

Does this make sense? I have increased my preload to take up the slack of an old spring, the seat is higher, the ride firmer, the chain is not pulling the output shaft apart when I'm on it, and the chain does not flap around when I'm off it (and so does not flap around when the rear wheel goes down a pothole, or a dip in the road)so will not fall off the rear sprocket either. Therefore, I'm happy.
ish.

[HelmetHair]

So that's all ok, then? Anyone out there thought "Blimey, he's right" or "cretin"

[chronyx]

I think you're completely right!

[Muckybill]

Keep it simple.
Place bike on centre stand and set chain slack to 70mm measuring under swing arm midway.

Ignore preload and sag.

When the bike is on the centre stand the shock has extended to it`s max length, this is where the chain should be adjusted.

If the suspension were to bottom out in use the 70mm is enough to stop the chain becoming tight and putting stress into wheel bearings and gearbox.

I adjusted my chain using this method from new (RD07a) and the c&s lasted to 42000mls approx using a scott oiler. Used the same method on a RD04 and got similar mileage out of chain.

After adjusting chain take the bike of the stand and get someone to sit on it then check if you can lift the chain of the rear sprocket at the three o`clock position. A very small amount of lift is ok. If loads, the chain is worn.

Bill

[HelmetHair]

Thanks for input-I reckon the problem with my bike was trying to get tension right with 1) an old spring-way too much "give" and 2) a chain that had seen better miles-
Muckybills posting is, I am sure, correct with a new bike and a new chain as he says, but with old/worn components it would be necessary to adjust the preload too, to allow for the dodgy spring
I'll leave this one alone now, as I am going to get a new chain after the next 1000miles, so will have to reset it then anyway-who knows, i may even get a new spring while I'm at it!
:P

[djadams]

Tightest point is always with the spring compressed (or removed and the swinger lifted) so the gearbox output shaft, swingarm pivot and rear spindle lie on a straight line.

If the suspension is set up as Honda intended, the rear wheel travel can pass through this point and out the other side, and the chain tension guidelines are designed to ensure that there would be sufficient slack in the chain to avoid the chain interfering with the suspension motion at this point.

Increasing pre-load will reduce travel, but it's not the correct way to do so - preload is intended to adjust sag. If you aim to reduce travel by increasing preload you reduce sag. As sag reduces, the ability of the wheel to stay in contact with the road over dips in the road surface reduces, which will give a skittish ride. The best way to adjust travel is to change the spring rate (with a stiffer spring).

There's no need to have anyone sat on the bike while checking the chain for wear.

[piguglyshandydrinker]

Tightest point is always with the spring compressed (or removed and the swinger lifted) so the gearbox output shaft, swingarm pivot and rear spindle lie on a straight line.

If the suspension is set up as Honda intended, the rear wheel travel can pass through this point and out the other side, and the chain tension guidelines are designed to ensure that there would be sufficient slack in the chain to avoid the chain interfering with the suspension motion at this point.

Increasing pre-load will reduce travel, but it's not the correct way to do so - preload is intended to adjust sag. If you aim to reduce travel by increasing preload you reduce sag. As sag reduces, the ability of the wheel to stay in contact with the road over dips in the road surface reduces, which will give a skittish ride. The best way to adjust travel is to change the spring rate (with a stiffer spring).

There's no need to have anyone sat on the bike while checking the chain for wear.

Helmet Hair, I think your'e thinking about this too much.

Suspension is designed to move, if you have the rear preload wound so tight that suspension never moves past half of it's potential movement, something is fundamentally wrong.

Best way is to remove a pivot bolt lift the rear wheel to find the tightet point in it's arc (in line with swing arm pivot, output shaft and rear wheel spindle) and the chain tight spot (if there is one) THAT is the tightest the chain can be, adjust to give a little slack, reassemble and take your own measurement with bike on the center stand for future refference.

Phil

[HelmetHair]

Thanks guys, I reckon you are right-I'm over thinking it.
Carbs need balancing too, and I'm not going to get involved in that, so I'll get a "proper" mechanic (ie not me!) to balance the carbs and get the chain/suspension set up right!

[XRV_AndyM]

Did a round trip from Ireland to Spain on a worn out chain and sprockets last year on my 98@. Drove to Costa Brava and Barcelona. Crossed North Spain and after a long ride from Biarritz to Paris the chain literally fell off on a bump when slowing down to get petrol. I rolled up to the Pump. Filled up the tank and slung the chain back onto the rear sprocket. Paid for fuel and then pulled the back wheel back as far as possible. I could still almost lift the chain off of the sprocket at this adjustment.

Drove from Paris to Roscoff three days later on the same chain and then drove from Rosslaire to Dublin. By the time I got home I could pull the chain off with my hand.

I replaced the C&S when I got home (Got a sealed chain, no split link) but I always ride with it a little loose as I can never really tell when adjusting if it's too tight.

My conclusion is that these motorcycle chains are very tough. And I would not worry to much about them slapping around a bit under the bike. Once you can't lift it off the sprocket with your hand then it ain't coming off. Having it too tight is not good at all. I have a scott oiler HCR kit fitted but I still use chain lube after cleaning the bike down.