have now taken off & cleaned carb three times but each time after a few minutes running it gushes petrol. I have read a fix where you drill though various ports on the carb as suggested by David Ryan (details below) has anyone actually done this? If so did it stop the leaks???

YOU NEED: 1. Flat blade screwdriver to remove carby.

2. Phillips screwdriver to remove float bowl.

3. 6mm ring or open end spanner to remove main jet.

4. 10mm socket to remove needle and seat assembly.

5. 2mm drill.

6. Loctite 3805 to fill holes.

7. Flat file to flatten brass filling sphere.

METHOD: 1. Remove carby from bike.

2. Remove float bowl.

3. Remove main jet.

4. Remove needle and seat assembly.

5. Flatten head of brass sphere at C

Simply adjusting the float height worked for me. Still, I think JLI recommend the drilling mod for the SSDT.

...has anyone actually done this? If so did it stop the leaks???

I did this. And it stops the leaking. I just jumped over this step:

6. Drill down through existing hole at C. You need to drill 28mm.

I don't think that this is necessary. (Maybe the older Mikuni carbs was a bit different, and there was needed this step, too?)

http://www.r2wtrials.co.uk/html_files/betacarbsetup.html