Hi Alan
Sadly, I haven't had enough freetime to clock up a few hours on my Moster yet, so I haven't encountered any of the following. However, one or two have clocked CHT of up to 300 degrees at full power. Could be that they'll resolve that with a richer mixture, although, in the abcense of a CHT guage, I will say that my exhaust went purple, even at rich mixtures for running in the motor.
A couple of guys had exhausts break. I think there is already a better one now.
There is a new recoil starter spring modification, but apparently, on it's own, it wont cure a problem which has been flagged up by more than one chap. That being, if the starter handle, or any exposed length of rope, is allowed to flap around in the wind, it will wear the rachet in the starter gear, to the point where, eventually, it destroys itself, sometimes letting the rope, and handle, go back into the prop. Lovely !! I also think that, if the handle is mounted to the frame, and the engine mounts are softish, the movement of the engine would probably cause enough movement in the rope to engage the dogs enough to cause problems. Looking at using a bungee to modify mine to copy Clive's idea on the Bulldog.
Dave