rear chain tension

[g.m.c.janssen]

Just fitted new chain and sprockets, the old chain was broken partially. Had luck that I saw it just in time.



But now completely confused how the rear chain tension should be set

1) The workshop manual says there should be a person sitting on rear part of the saddle, the owners manual says without a person on the machine

2) the text in the workshop manual mentions a rebound range of 15-20 mm; the figure shows a 15-20 mm distance between chain and swing arm, this fits better with the text in the in the owners manual; but it mentions a minimal distance of 15-20 mm, so 30, 40 or 50 mm would be OK too, I doubt

So what is the correct procedure?

[Mc tool]

I hope you didnt get the same chain , looks light weight ,like maybe for a MX bike. Could be why it broke , also could be over tightening chain.
The chain tension changes as the rear suspension moves up and down . The chain is at its tightest when the output shaft (with front sprocket on it ) the swing arm pivot ant the rear axle are in allignment . At this point the chain should have minimal slack but not be pulled tight . If you can be bothered you could use a ratchet tie down and pull the suspension down till these pivots are alligned and set the chain tension to have next to no slack ( but not tight or stretched ) and then release the suspension and see how much slack you now have . This is your correct chain slack ....usually about 20- 25mm .
Chain slack ,(clearance ,tension , whatever you want to call it ) can negatively affect gear changes . If the chain is to slack it can make changes clunky and can even cause missed gears if you have a delicate toe . To much slack can also cause excessive transmission snatch. Properly set up (chain tension ) and well coordinated ( throttle hand and left foot ) your gear changes should be almost be a instinctive thing.
I have had good success with DID and RK
O ring chains but you gotta get the heavy duty ones with thick side plates ...not 125-250cc mx bike chains. A good chain on good sprockets that is cleaned and waxed should last 20,000 miles.
I use water soluable areosol degreaser and a paint brush to clean chain ( on the bike )and when its dry I used Maxxima areosol chain wax ( doesnt fly off ). Remember you are only lubing the chain to sprocket contact and a wee bit on the o rings so you dont have to put heaps on . I liked to clean and lube chain every 1000kms ( 600 miles ). Piece of cake :-)

[randtcastell]

Thank you for your excellent post. I always learn from you. Cheers! :^)

[g.m.c.janssen]

Mc Tool, thank you for your extensive explanation!

Will check again if my new chain meets specifications. It is a AFAM 520 XSR specified for Ducati 907 and others, the broken one was the same size from DID

[Mc tool]

I had never heard of Afar chains ,but then I haven't bought a chain for more than 10 years , certainly looks the part , them Japs make some really good quality stuff and if it's the one the recomend .....
One thing I omitted in my previous post is that the rollers also need a bit of lube . I usually get a longer straw for the aerosol can as it slows down the delivery rate and if you put a kink in it can help your aim . I aim for the spot where the rollers and side plates meet . I lift the back wheel on a w/shop stand . :-)

[g.m.c.janssen]

Hi Mc tool, sorry but I didn't get your last point about the rollers

[Mc tool]

The rollers are the little steel tubes that contact the sprocket ,situated between the inner side plates . These roll around the bush between the inner plates ( you cant see them) pin that link the inner and outer plates . You need to get a bit of lube between the pin and the rollers .
Google roller chain link ( I cant figure out how to post the pic here) and you can see the side plates , pin , bush and roller

[higgy]

[Mc tool]

Ah Higgy ,you clever bugger ......so whats my feckin password ? My smart phone logs on automatically but my laptop ...not so much , and Ive lost my note book with all my passwords ( I think Di chucked it out ). Just gettin old .

[g.m.c.janssen]

Thanks for all suggestions and clarifications! The chain has been fixed with the additional lube between pin and roller!