I'd be cautious about launching anything quite that niche into the current magaine market – the newsstand is in terminal decline with all the major players looking at web media as a means of survival. The biggest problem with mags is the advertising – great in theory until you try to prize revenue out of the market, especially in this climate. Very few niche magaines can survive on cover sale revenue alone, it really isn't that much and in truth probably wouldn't even cover the origination costs.
That's not to say there's not an alternative. Take a look at
http://www.gpweek.com
E-zines have a lot going for them (one of the reasons why so many of the major players are looking so closely at them) – you can still sell the advertising space to make it into a commercial venture (adverts in e-zines can offer click-through links to respective websites), but you remove the big overheads of paper, print & bind, distribution. A big plus is the opportunity for dynamic content, motion, sound etc. And you can offer a pdf download feaure and an archive of back issues.
Some will say 'but you can't charge for it', but that misses the point – advertisers don't care if you sell your mag or give it away, all they're interested in is how many people get to see their advertising – the higher the circulation the more you can charge 'em.
At the end of the day could we, as a community, sustain the sales figures needed to keep a printed publication in circulation – I somehow doubt it. But a Retrobike e-zine could give John an opportunity to generate some solid revenue.