Suzuki GT500

[MARTIN46]

Hi all,
I have a 76 GT500 as a TR500 replica with individual foam air filters and expansion chambers (Higg Speed) it has also been ported, I took it out for its first run and it wont rev over 3000 RPM it just splutters if apply the choke it gets worse, has anyone any idea re what the jetting and needle settings should be as I am now struggling, plug colour was OK maybe a little on the dark side, any help appreciated.
Martin.