i was told that if i replace the rear sprocket on my 1000ds (from 42 teeth to 44) the chain slack recommended by ducati 38-42mm changes. is this true?
Changing the rear sprocket for a larger diameter sprocket will mean that you have to move the adjusters to get the recommended slack from their original position. A larger sprocket will mean the chain has longer to run so the adjusters need to move forwards from where they were to give the recommended slack. I'm not 100% sure if I have answered your question but let me know if not
my question was whether the slack still has to be 38-42 as per the sticker on the swingarm when changing gear ratios?
The chain slack is merely an allowance to take into account the effect suspension movement has on the chain tension. I would not expect a change in 2 sprocket teeth to affect the static free play. Yes, set the slack the same.
To my mind the required slack in the chain is to allow for the offset between the centre of the front sprocket and the swinging-arm pivot and the effect on chain tension that this has as the suspension compresses throughout its range. A change of rear sprocket shouldn't effect this in a meaningful way. Ergo, the std slack will be OK.
Although I'm not entirely sure it's a wise move to replace the (one) sprocket and not the chain. It is usually recommended to change them all together, both sprockets & the chain, as a set.
No, you keep the recommended chain slack the same. Do check however the chain as fitted is long enough to accommodate 2 extra teeth on the rear sprocket AND maintain the recommended slack. Depending how many links are in the current chain you may need a longer chain for the larger rear sprocket.
