Considering the likelyhood of a crash or engine going pop, I'd have thought a van was essential. If you consider that european break down cover will cost you about £70 per bike, then hiring a van will probably work out cheaper.
If you camp, you'll need a van to take the gear - look how much I took last year:

F1 hotels are cheap enough, but you'll bump the cost by having to eat out every night. Camp sites are usually between £5 and £15 a night, depending on whether there's a pool!
Not saying it can't be done on your NSR's, just that I've done a lot of touring, and have learned the hard way!
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball
