Thanks daviee and robbo. I read recently that the colour of plugs is more to do with finding out if the plugs heat range was suitable. Anyhow, since the carb strip, clean and balance the engine runs fabulous. My concern was that I was unable to adjust the seized mixture screws and would be stuffed if the lower rpm range was incorrect, I know a colour tune might help, but at the moment all seems fine for a 47000 mile engine. I've done some high speed / high load plug chops on other bikes and it's quite 'ahem' exhilarating 🤪. I noticed there's only 3 clicks left on the cam chain tensioner so it'll get chain and valve clearances done when the snow comes.I read on here that the oil light isn't for pressure but for oil level, while out checking the engine through its rev range for any running/mixture issues I noticed the oil light flicker at high revs in 3rd gear when the front wheel started lifting, I'm presuming (hoping) this was just oil surge to the rear of the cases. No oil loss and level to top of sight glass.
To clean the inside of the sight glass throw in a handful of iron filings with the oil and the run the engine and then you can use a magnet to pull some filings to the inside of the window and wiggle the magnet around and clean the inside glass.