Is that a Lammy with 12 wheels or a Lammy with 12" wheels
Your problem could be the petrol tap full of poo or the petrol cap breather blocked ??
There's a guy in our club with a LC350 engine in a GP200, now that is scary !!
I had the same starting problem,spark then no spark,took off the pick up coil,cleaned it and now the bike starts fine.I hope that this has solved mine.