ST70 Will only run on choke ! Help

Hi all....... Got my Lady Dax booked in yesterday for it's Mot after a Year of putting it back together.
The problem I have is if the choke is off and you open the throttle there is no power it justs dies!
If you run it with the choke on you can get up to 25mph out of her.
Very strange.The good news is it passed it's Mot.
Just got to get this sorted then will be using her for work.
Any help much appreciated.

Cheers John

Clean the carb completely or get a revision kit.
Renew the gaskets.
Set it up right.
Renew the spark plug.

Thanks for that Waynus ......I have stripped it all down today and ordered a new gasket set.
When I come to fitting it back on bike what is the best way of setting it up?
Any hints or tips would be grateful.

Cheers John