gpx250 valve trouble

[seasalt]

I accidentally posted this in zzr forum, and not getting far.

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. (What the ??!) 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?

Haven't had any luck finding answers on that so:

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?

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

[Martin]

i've got an 89 gpx 250 and im rebuilding the engine right now, but i dont have any valve problems...its an old worn out engine so if there is a common problem then i should be experiencing it too, right? i've just got the usual gasket problems

[Marty ZZR rider]

You could try this:
<http://cgi.ebay.com.au/GPX250-Kawasaki-2006-Motor-engine-can-freight-20300km_W0QQitemZ260382489256QQcmdZViewItemQQptZAU_Motorcycle_Parts_Accessories?hash=item260382489256&_trksid=p3286.c0.m14&_trkparms=66%3A2%7C65%3A1%7C39%3A1%7C240%3A1318#ebayphotohosting>


I will also add, I have no interest in this sale
Good luck

[seasalt]

Thanks for posting guys.
I agree it is not a normal problem. The seats are not damaged, but the valve face is worn away.
We got onto some stainless valve blanks within spec, so we'll try that.