Based entirely on my (slightly dodgy) memory and a bit of lateral thinking I think he must have been on a V4 for the F1.

It was listed as a Honda, he was a works rider so I think that's the only option, although I seem to remember that someone, I'm sure it wasn't Honda, had a go at producing a budget racer around the CBX750 that was available at that time.

When Sticky re-appears I'm convinced he'll have a photo that will settle it. Over to you Sticky