Hi Mick
First thing I would do is another plug - I have had a couple recently that wouldn't behave until another plug with a slightly larger plug gap.
Think these take a bkr5e plug?
The other thing I had a bit of luck with was a quantum with similar behaviour was to arc up the RPM to 3400 and spray this down the carby until it nearly stalls but doesn't. Do that about 5 times.
Then put back to idle and spray until it stalls. Leave it half hour and start it back up
https://www.repco.com.au/en/oils-fl...-conditioner-240ml-6601n-240/p/A9412003?
