I'm hoping that I've FINALLY found a good Heavy Duty alternative for the old YB16AL/A2 for my 900ss - funnily enough its a BMW spec for a bike that I used to own!
519-013-017
Here is a link to the guys that found it for me - they have been excellent so far - very helpful and good prices:
http://www.mdsbattery.co.uk Cheers - Frank
ps - two things they did mention - Varta use differing codes for the same battery in different parts of the world (confused ... I was).
and that Varta and Yuasa source their batteries from the same manufacturer ????