Having a bit of trouble with my gk76 sp. I bought the bike as a non runner, I stripped the carbs and replaced the o rings with a viton seal kit from litetek. Put all back together. Did not adjust any float heights but set the air screws to 1.5 turns out. Basically when starting the bike with choke it starts on 2/3 cylinders and then comes on all 4. The bike will idle but it won't take a rev at all. It just bogs and then cuts out. If I feed the throttle slowly it will rev up to about 6000 rpm but it's very fluffy. Has anybody experienced the same issue?

Hi, have you got the airbox fitted back on? These bikes are really susceptible to fouling plugs I've found, and once fouled it's hit or miss whether they clean up again. I left the choke on my well set up 73sp on a TD session, and it fouled the plug, and had to replace them.
I may be able to help more with more info.

So today I stripped down the carbs again, I set the float heights to spec (2 were slightly off) and I also raised the needles slightly putting the clip on the third position. put everything back together and back into the bike. Balanced the carbs and now there is a bit of an improvement, it's not fluffy like it was but the bike still does bog slightly when revved suddenly. Would bringing the mixture screws out maybe half a turn help the bog issue or are they only adjusted for idle?

Pilots control idle + up to circa 1/4 throttle position. Especially when revving engine suddenly from idle. But before you go and fiddle with carbs check that everything else is fine. Is you fuel supply and valve clearance setting in spec? Also, do you have air filter / exhaust can mounted?