I just set up my first bottle-generator light system, using a cheap old dynamo (bought for a buck at a bike co-op) and a Busch & Muller Lumotec Oval headlight. I don't know what brand the dynamo is (it's got a "C" on the cap), but it's definitely low-end and old. Anyway, it feels like a BIG drag on the tire; I'm wondering whether A) they were all just like that, or B) I've got it set up wrong. If A), are the modern ones really any better? Advice on proper setup will be appreciated.

I keep hearing people say that a bottle generator shouldn't produce noticeable drag, but this one definitely does. Maybe I'm doing it wrong?