Thanks for the replies, guys.

No definitive answer then?

I've removed the engine from the frame now so that I can give both of them a good clean up / check over & will check the valve clearences on the engine while it's out.
I'm now seriousley considering buying & fitting the less restrictive stainless steel down-pipes from Sandy Bike Spares via Ebay.
So, does anyone on here, with a non SP model GK76a, have a K&N filter with the LARGE inlet rubber fitted & a Scorpion end-can fitted to the above down-pipes?? If so, could they advise me please what size mainjets, needle clip position & pilot jet size to start with. Would 112.5 or 115 mains, needle clip moved from the middle slot to the 2nd from top slot & stock 47.5 pilot jets be a good place to start & then fine tune from there ??
Cheers.
Wullie.