Here's the service scedule for a single spark 650, only difference is the fuel filter is now recommended to be changed at 24k, However the general consensus is to only change the filter if or when it becomes blocked, it's around £65 ffs
As for the valves, a bit of a fiddle, damn right they are. Takes me around 3/4 of an hour just to reach em through all the plastic and other bits.

Not too bad as the oil tank needs to come off to be drained properly and the battery can have a quick charge whilst it's out.
I'm coming up-to 24k miles, I should be able to do a complete service for under £70

£20 for the service kit which is two spark plugs and an oil filter, the rest on oil, coolant and consumables. I have a k&n oil filter that'll just need cleaning and oiling, everything else on the service schedule gets done as and when needed
