Wow, I'm surprized nobody answered this. The specs in the back of Pete Snidal's service manual say the chain is 5/8 x 3/8". So that would be 530. You'll need a non-oring chain BTW. An oring chain is too wide and will hit the chaincase.
hope that helps, Debby '03 500ES
Re: chain size bullet#151626 05/30/057:13 am05/30/057:13 am
The other question is - how long? I don't know but I could count the links on mine if that would help. Or you could just give Classic Motorworks a call. They have chains for $29.95. With the Bullet's modest power you don't need a high-end chain!