GPZ250 intake valve wear problem

[seasalt]

I've put this in the wrong forum. great start. Can a Mod shift it to GPZ please?

My 17yr old son bought a '96(?) blue black GPZ250. Within three week it slowly became impossible to start.
Inlet clearances had closed to the point where no adjustment was left.
Disassembled it. The intake valves had worn their contact face away. We had the engine rebuilt, including new valves.
In 2000klm the clearances had closed up again to the point where it wouldn't start.
Disassembled it. The intake valves had worn their contact face away again. Neither the mechanic nor myself understand why
it would do this. We are thinking Kawa spares may have a "bad" batch of valves, for want of other ideas.
We thought we'd get stainless inlet valves, but after trying his suppliers the mechanic said the stem and valve size were not common, and he couldn't find
suitable blanks or a close match.

He suggested I ask on a Kawasaki forum:
Do ZZR250 valves fit straight into the earlier GPZ250 motor? Are they different? He is assuming they would be improved spec.

Anyone else had this valve wear problem?

[mike-s]

Dumb question, but you didnt add any valve lubricant to the fuel? the bike didn't have hard valve seats did it?

[seasalt]

I doubt "upper cylinder lubricant" would make that much difference. With or without, 2000k is a very short life.
As far as I know valve seats are refaced originals.
I would not expect an honest answer about its history from the guy we bought it off as we feel he knew this was happening.
Saw him at servo and he saw me but pretended not to and drove off. Oh well, "buyer beware".

Its not normal I know, I've searched for posts on valve wear and found nothing like what our bike is doing.

Are ZZR valves same dimensions? Anyone know 4 sure?

[mike-s]

originally i had put in "I'd just suggest trying to find a spare head and go from there. Might be better in the long run to be honest.."

then i re read "The intake valves had worn their contact face away again" do you mean it wore away the face on the VALVE ITSELF? or (as i originally read it) the valves wore down the seats in the head?

if its the valves, yeah i'd seriously start trying compare valves from a zzr250/gpx250 those of a gpx250 to see. They are both 8 valvers, aren't they? if so im sure as the gpz became the gpx there's a fair chance a decent portion of the motor may be the same.

[seasalt]

Have just been Googling for a head. No luck. Found a zzr motor, but that's an expensive fix.
Anyone got a '96 or close, gpz250 spare head on a wreck or something?