Leaderboard

It sounds to me like it's leaning off after a certain point... almost as though one of your jets is blocked.

try opening the carb bowl drain screw (fuel tap ON) before you delve too deep taff just incase theres a drop of water in the bowl

Sounds to me like the throttle cable free play needs some adjustment. An easier way to test the speedo cable by the way, disconnect it at both ends, and then twist one end with your fingers, you should see the other end move. If not your speedo cable is broken. If it's moving when you twist it with your fingers, then connect it to your hub, turn the wheel by either pushing the bike or have it up on a stand, and just watch to see if the other end of the cable moves. If it doesn't, try pushing the inner cable down into the outer cable a bit, and repeat the process to check if it's moving with the wheel. If not then your hub is the culprit. If all is fine here, then reconnect it to the speedo, making sure that it's properly seated and threaded. If you're still having no joy then the speedo is your culprit.

FFS then I really am in trouble!!