2018 GP300 not starting / breaking kickstarters

[Undertow]

Some answers for very good suggestions:

- The coolant level is ok. Hydro lock would have been a good answer, but not this time.

- After putting the plug back the engine gets hard to turn right away.

- No extra fluid (water / petrol) coming out of the plug hole when turning the engine.

- No extra noises (as said before) when running, but really crappy running at lower rpm's and strong kick later, like my TE125 (original needle, and through this forum I know what to do, thnx).

- Have to look for the vent hole. A new one for me too, but if there is one it could be the reason (the starting got worse and worse until stopped totally).

- If the oil is to blame then the original oil is wrong one. The first kicker broke around 2 hours of riding.

- The design of the kicker is bad. The cam on the kicker puts forces in place that can't hold it well. All three have failed the same way as the one in the picture (see attached pictures). Just today got a new one with different design, this looks like it will hold better (the third picture).

- Maybe I'll install the kicker, get a new battery and try once more.