Drilling the slide is only to do with throttle response.

Raise the needles too much and you get a flatspot due to it being too rich.

Have the needles too low and you also get a flatspot due to it being too lean.

The air/fuel ratio needs to remain on the right ratio constantly throughout the rev range for the bike to run perfectly.

Ok i will try no washers on the needle and see how i get on.

What do you have on there now?

Go down in 0.5mm increments, might save you from taking the carbs off more than once

There was the standard half mil ones on to begin with then i went up to 1mm washers with no difference

Just get it on a dyno. Anything else is guess work.

Sorry for the delay updating, been away to the northwest 200 and only got time at the weekend to get back to the bike. I have now removed the washers altogether on all needles but this has made no difference at all. It has been suggested it is running too rich and not lean but having gone from standard jets to bigger it did improve upper rev range.

My guess is that it's running lean, typical symptoms when too much air (or not enough fuel) is getting in.

You sure you have the stock rubber flap in place? Part 15 here: http://www.akhara.com/nc30/nc30parts/files/51.htm

Stock needles fitted (marked 'J51')? Stock pilot jets fitted (#35)?

Something's amiss...

Just like to thank everyone with suggestions for the vfr but no longer need to worry. An ershole in a Nissan Quashqi pulled out in front of my son last night resulting in the bike going under the car and my son into the wing. He is ok a bit sore today but the bike is dead. Once insurance company have sorted things out i will list for spares if anyone interested.

Shit..

Glad your lad is OK - that is what matters.