You think it needs some Hawaiian flowers and a "mystery machine" log on it Stefan? 

Horses for courses Nick, and across the web differing opinions exist. Sprockets for 219 tend to be smaller in diameter for a given tooth number and the chain runs smoother but is potentially weaker than a larger pitch chain. See this article... https://cutpriceracing.com.au/store/Page17/
420 chain is for motorcycle applications up to about 125cc usually, so, arguably, as we use a similar size wheel and have a similar torque transfer as a 125 to it, it should work out fine.
If you hold store in the article I sent you above, and I am not sure I do, then 219 should break more readily. I have not heard of a 219 chain breaking on any of the cyclekarts so far.
This probably has you no wiser 
Also this... https://gokartnerds.com/how-to-select-chain-for-go-kart-and-minibike/?utm_content=cmp-true

Jim

Don't fry me any bacon :-) not my bag. Left or right is the same to me, if I were to express a preference, I dress to the left 
The questionis do I turn the tyre around for an anti-clockwise track??? 

Loving the engine bay, it's looking very good!

Looks like we have a show with at least four cyclekarts! Should be good static or mobile. I have de-pilled the tweed jacket, polished my helmet and packed the funky trunk into the boot of the tow car. I hope that the overalls still fit.
Any news back from VSCC greatly appreciated.

Thanks Stefan, on the Silverstone website, it looks like the historic testing sessions are on the Friday afternoon. As we are not testing, it looks like from this that it will be a possibility. There seems to be no way of connecting to an actual human being on the Silverstone site to verify this though. A contact for the VSCC might yield an answer?

Unless you are lucky Stefan, and a clothes peg yields the perfect one, it might be your best shot. 

Another puzzle another legend, this time with cryptic and straight forward clues, choose your weapon!