Stock is 13/42 on all but the Moto. DID X-Ring chain is an awesome chain. If you are buying new, get 100 links and keep the cut off piece for possible future gearing changes.
Jess,
Get a 40t rear for that new motor of yours to go with the 14t front, you are going to need it and the chain size can remain the same as stock.
Well, thats if I can get the new motor. I haven't been able to contact Timbo. I haven't tried calling him. I figure he is busy and I'm in no particular hurry right now so I haven't bothered him by calling. I guess I'll give him a shout sooner or later. But I need a new chain now. I get a good deal at my local shop on the chain and they cut it down for free.