Modern Vespa

For a VBB, VNB and other vintage bikes, is it customary to richen the mixture for the cold weather months?

i tend to run a hotter plug ( b6ES for Lambrettas / P-series, ...BHS for your VBB ) ... to make it easier to start.

And it's going to take a little longer to warm up.. but other than that, should be the same as always. I wouldn't screw with your jetting.

what are the different plug choices? ie: what do you run in spring/summer and winter/fall. I converted the piston to a dome type with the appropriate head when I rebuilt the motor and there is a champion RN2C in there now, I believe.

I always run NGK plugs .. normally B7's, but in winter i go to B6's.

For your bike, look up the champion / NGK conversion of NGK B6HS

Does the conversion change the spark plug rating? There is also 2 types of plugs long and short-whats the difference?

No ..there's an equivelency chart that gives the comparitive plug between brands.

Short threaded plugs tend to go in all smallframes, non-sport models, ( VBBs/Sprint / Super ) .... long threaded plugs go in any sport model ( GS / SS / Rally / P200 ) and all lambrettas.

I meant the cylinder head/piston conversion-does this change the spark plug rating.

Also, I'll note: P200s take the B*ES (long) plugs, but 125s and 150s take the B*HS (short) plugs.