GRiSO 850 intermittent start

Hello all, My 850 GRiSO is not behaving I bought a new battery to eliminate this item but the fault still exists.this is an intermittent issue and sometimes the bike will start perfectly. 12.5volts measured at battery and at starter motor.
When I press the start button I can hear a clonk at the starter motor and then another clonk when I release the starter button. Any advice would be good before I pull the starter motor off and test on the bench.

Sounds like the classic 'Startus Interuptus' or poor earthing. When it goes 'Clonk' does the dash go blank?

Pete

no blank on the display. Will check out the earthing tonight thx mark

Ok, earth checked 0 ohms on meter and cable looks in ok condition removed conection at stud near starter motor and cleaned cable ends and all ok.
Removed starter motor and noted top bolt thread gone in starter motor housing , possibly a bad earth here, so modified longer bolt and nut for a secure fitting. Tested now and still intermitant starting. Removed starter motor completely and set in vice on bench connected battery and tested perfectly every time.
Starter motor back in bike and still intermitant starting. Tested 12v from starter switch.
AAAAAAAAHHHHHHHHHHHhhhhhhhhhhhhhhhhhhh.

there is a cure Mark, as Pete says. Often called "startus interruptus" and exhibits just as you say. search for it on this site for a cure.

Searching now, thx