Hi Susanne,
Firstly, stop using the Easystart - if the bike won't start on petrol, then there is a fault which Easystart will make worse, not better.
If the carb is OK and the spark is timed correctly, I would check out the 'O' rings on the induction pipes.
Try wiping a thin smear of silicon rubber around the joint of the pipes and alloy ends, leave it to cure overnight. If the bike then starts OK, the 'O' rings are at fault and need replacing. The one at the bellhousing end is a normal 'O' ring but the one at the cylinderhead end needs to be nitrile as it has to withstand greater temperatures. The use of the silicon rubber is only to find the fault and should not be used as a permanent cure - contamination with petrol will soon destroy the seal again!
If you are a member of the LDMCC, the correct 'O' rings are available from club spares.
If you are still using the original distributor, set the points to open at about 5 degrees before top dead centre. After you get the bike running, you might need to adjust this figure to improve the performance.
Regards,
Eddie.