My R50 runs now….as a 250.  I'm hunting around for a 6 volt (told you it was old) timing light to see what theat may tell me but between one thing and another (these “things” are 4 years old and 15 months old…) I think it may be better to get teh bike to someone who knows and can work on them so I can get this firing issue sorted and get teh bike through compliance etc. Odd thing - ran on two before.  Had B8HS plugs which worked until recently - swapped them for B6HS plugs that I had lying around and it worked again...then the LHS cylinder decided to not fire (exhaust cold, removing plug made no difference).  Fuel is getting to the carb and disappearing into the cylinder.  Spark is sparking well when I tried it on the barrel and there is compression - all the components for making a bang.Can I use a 12 volt timing light on a 6 volt bike?  I ask as any mention of 6 volt to the pimply youths in Rep/Appco etc bring about a rather blank stare...Edit - need the mechanic/bloke who knows in Auckland - preferably the North Shore