I tried the larger squirters with limited success. To start, jet that puppy bigger 2 to 4 sizes per jet (primary and secondary) if the problem gets less, you need more fuel from the accelerator pumps. I believe the 650 comes with 31 nozzles standard. Going bigger doesn't help as the 30 cc pumps don't have enough volume per stroke to spray the fuel in as it is needed. I put dual 50 cc pumps on mine with 31 nozzles and I used the brown pump cam, turned it so it was about to push the accelerator pump lever, marked it and drilled my own hole. Hesitation went away for me.
You need more fuel, the manifold is fairly big for that combo, it has no exhaust crossover to heat anything so it needs more fuel.
This is all assuming the engine is happy and the carb is as well.