I have a 42 wm20 bsa it has been resting for 43 years, I have had the magneto rebuilt by a professional , I cleaned the carby, new spark plug, I'm mixing 91 & 98 octane petrol with upper cylinder lubricant . It's taking about 20 kicks to fire up cold and 1 hot , outside temp about 15 degrees c .
Any cold starting tips would be appreciated ,
Turn the petrol on...Depress the 'tickler' on the carb for a few seconds, but not long enough for petrol to be pouring out of the carb...Some experimentation will be needed to determine exactly how long to depress the tickler....No choke.
With the adv/rtd set at fully advanced try to start the bike, leaving the throttle shut until the engine fires....As it fires 'catch' it by gradually opening the throttle...Don't 'twist and kick' as M20s start better on a closed throttle initially..
If it kicks back retard the ignition SLIGHTLY...Only retard the ignition enough to stop it kicking back (if it does). If it is over retarded it will be hard to start...You'll soon get to know where to set the lever after a few starts....
If you haven't already set the spark plug gap to .018"...I'm assuming all other settings, carb specifications. etc. are correct..Ian