In Oregon, at least, there's no distinction between a DUII (driving under the influence of intoxicants) with a car vs. a bike. They lead to the same penalties, etc.

That said, I'll never drive a car after drinking, not even a sip (been there, done arrested), but I'll get on my bike after a drink or two max. (Edit: by the way, my attitudes toward drinking and driving has very little to do with the legal ramifications any more.)