Hey everyone, I've just picked up a 1990 GS 500 E which is not running etc. Apparently its been a project for at least two people before myself so who knows what i will find hey?. The list of problems I've discovered so far is holes in both Carby diaphragms, pilot screws are butchered, Camshaft Cap has a stripped cover thread,  spine on gear change shaft and lever are toast, cam chain tensioner busted and cam timing wrong - Yikes!. This leads me to the most significant problem, the exhaust stems look damaged. I can see light through the exhaust port valve seat with the head off, all caused i imagine by them hitting the pistons. Anyway, my question to all the GS experts is, will a 2001 cylinder head go on my 1990 motor?  If not, do you think I could take out the exhaust valves and install them in my head? Any advice is appreciated. Cheers ~ richard (Perth Australia)   

yes it will.

and yes you can remove the exhaust valves and move them to a new head.

There are two differences; color and presence of a mechanical tachometer. Your 1990 has a worm gear for the tach, but I don't think the 2001 head will. I'm not actually sure when the switch to a electronic tach happened.

I've never done the swap, but I would guess that if you switched heads you would need to either get a 2001+ tach and wiring harness or go to an aftermarket tach that picks up the rpms from the spark plug wires.

Heads have mechanical tach drive on 89-02 models.  The electric tachs started with the 04 year.

The 2001 head does indeed seem to have the Mechanical Tacho, so it looks like I'm good to go then.   Many thanks for the help and input, much appreciated. I've learn't heaps already from this excellent community, and look forward to contributing myself in the future. Cheers ..