Can anyone tell me if the 17" wheel from a 1994 FZR600R Foxeye (4JH) will fit a 1990 FZR600 (3HE)?

Alex.

With a 160 wide tyre, it should do after a bit of spindle modding. Just beware though, that if you don't fit a suitable profile of tyre, your speedo will be miles out.

The Foxeye has a 160 tyre as standard, so that would not be a problem.

But there will need to be some modification to the axle?

I'm not sure how the tyre profile will affect the speedo, it's driven from the front wheel.

Alex.

Sorry, my bad. Didn't mean to put speedo down. At my age it's easy to get distracted (I was on the phone to a customer at the time talking about a similar issue with another bike).

If I remember correctly, the axle spindles are a different diameter so you will need a spindle from the 4JH.