Still having the same issue.
I have sealed exhaust (it was the joint between box and U bend I was on about) Made no difference
When it started I left it running for a good 5 mins before switching off the choke and it stopped, when I Kicked it over again without the choke it started, if I put the choke on it revved up it didn’t cut out.
Took carb off to check my jets and they were as had written, when I put it back on It would not start
so I fitted the old original sh1/18 carb which is 50 choke, 5889-2 atomiser with 105 main and 45 pilot ... would not start
Not sure where to go with it now
If I could get it started I would check my stator settings again but it was set up with a “buzzwangle” so pretty sure it’s correct. As I said before it’s a new BGM stator that read ok.
Could it be todo without piston rings but compression seems ok.
I have a Casa 185 kit I could put on but would need another carb for that....starting to become a nightmare
Good job I have another to ride on