After trying out numerous mods that didn't work I went back to stock. My problem now is that with the stock carb setting I'm getting popping sounds in the intake. My fuel mixture screw is at 1-1/2 turns out, 157.5 main jet and clip at 4th groove from top, all stock settings before I tried all the mods. This happens at low to mid throttle. Just before I went back to stock I tried the clip on the 5th groove & 160 main jet and it fouled the plugs with black soot. Would you have any advice on where to go with the stock set-up from here ?

You might have tight valves, you should adjust your valves and do a compression test and get back to us.

The valves are non-adjustable on the 700 as I am told.

It uses hydraulic lifters and there is no adjustment. Are you sure the carb adapter isn't torn? The jets and needles sound right. You might want to check the float level.

OK so it is not the valves, but you should still do a compression test. Then look for carb adaptor leaks. Start it and let it idle then spray carb cleaner or something like it all around your carb and boot. If the idle speed changes you have a leak somewhere.