MF, the few things I would be checking first would be a marginally lean mixture (hence hotter but also explains the hesitation) or if the governor butterfly moves freely ( have seen a few where the plastic has aged and when it expands with heat its base rubs/binds on the coil and wont increase revs as quickly.
With this carby, the choke acts as an accelerator pump – it shuts partially when the throttle is opened to richen up mixture. If the mixture screw is not opened enough, the choke will jamb full on and try to pick speed up. Problem is since there is no limiter, it goes full on and bogs the motor down.
Probably good for Cam to check the same things with his as any of these will make the motor feel down on power
