Richard I’m a big guy also 6’2″ 220 and it’s true we are to big to take full advantage of karting “But” you can work on your race craft that will get you closer. I’ve tried different gears and you’ll suffer up top or on the bottom . I don’t road race so it could be different but I gear for a little more top end because I’m better/Faster in the tighter stuff I loose on the striaghts and get it back in the turns. If I’m clean and carry as much speed as possible even with a shifter.
I did a challange in rental karts 2 weeks ago on a pretty tight track I had the 13th Fastest qual timeout of 36 drivers I was the biggest of all the drivers. I tried to be as smooth as possible and didn’t over brake. A 6th and two 3rds in the heats. My team mates didn’t do as well so finish not so good. :(
I run a KZ kart and the power is different but when your 40lb heavier than the rest there really isn’t alot you can do that 40-50 puts you a second and a half off the leaders.
Try and find a gear you feel comfortable with and work on your race craft and be smooth don’t over work the chassis let it do it’s job. A very good driver once told me drive like your the only one on the track and it dosen’t matter ! you’ll go faster when your calm and not forcing yourself.