[K1W1]

Exhaust:
Will an early model exhaust (header, muffler, the whole thing) fit onto a 2011. Might sound weird I know but one thing we are looking at is to sace a little weight if possible. Not so much interested in more HP, tork, noise etc but if that comes with it it will be a bonus. Secondly, if it will fit, is it worth the effort. If it will only save me aobut a kilo or 2 might no be worth my time kinda thing.

There are two exhaust systems for the 650. Pre 2007 and 2007 or newer. Anything designed for a 2007 or new 650 will work. Staintune make one if you want to shop local.

Is it possible to convert the duel exhaust on the 1K to a single similar to the 650. Thinking being to save a little weight again, but also free up a bit of space to put on a tool tube. While I'm sure it's possible (isn't anything) is it worth the effort. If I was to loose HP, tork, ridability etc then might not be worth the time and effort

Anything is possible with enough effort and I seem to recall that it has been done but whether it's worthwhile financially is another story. Changing the mufflers to something lighter is probably the best bet.

Oil cooler:
Has anyone converted the air cooled oil cooler on wither of the stroms to a water cooled one similar to what is on the 1250 bandit and what looks to be fitted to the new 2012 DL650. When we got the mrs bike a few months back the first thing I thought of was a water cooled oil cooler (well, a heat exchanger really) and wandered if it would work. I forgot all about it for a while until now and then started thinking it might be able to be donw to both bikes and wondered if anyone had done it.

I don't think anybody has done that and to be honest I can't see why you would bother, For all the panic and worry people have about the oil cooler location there are virtually no reports of damage occurring to them and the motor is bullet proof as it is so you would not be improving reliability in any way.