Scooter spluttering

Hi, i have a Suzuki Katana AY50WRY LC 2000.
I have a 70 kit and new crankshaft professionally set up and run in.
Recently only about 20 miles ago had Mallossi 19mm carb and a new mallossi variator fitted professionally.
When i pull the throttle back a little or to half way it splutters but if i nail the throttle it sounds fine, surely this is not right?
Also when going down a quite steep hill the bike doesnt rev it just rolls and wont rev until its back down to about 30mph!

Thanks for any help!

 

I think a gear bearing or a crank bearing could of gone, could it be this?

 

If the bearing had have gone, your bike would be fucked right now!

 

Okay, any ideas then?

 

I think it's jetting. Has it been jetted properly? Take your plug out and take a look at the colour of it

 

i'm pretty sure its something to do with jetting, try taking the float bowl of your carb off and take out the jet, and just see if its blocked, blowing through the jet with your mouth will clear any blockages

 

Thanks for the replys
It shouldnt be the jet as a scooter shop did all the carb and set it up but i will have a look and let you know!

 

And the plug was a blackish coulor and i replaced it