XR250S Oil pump failure?

[miss P]

Hi all,
This is actually Mr P, who has offered to help a friend out with a top end failure of his 1996? XR250S.

Here's the brief story,

This bike may have been used for trail riding, but is now used on-road by a sensible mature rider.
The engine oil was regularly changed, the oil level was checked and topped up 2 days before the failure.
After failure, the bike was taken to a local bike shop, who said there was no oil in the frame and after stripping the top end, had found the camshaft had snapped, followers completely worn away.
I recovered the bike home to find the reason for this failure, I thought, blown seal, blocked oil way or other minor cause.
However, there was no signs of external leaks, so I removed the sump drain bolt and found that exactly the right amount of oil came out.
It would appear that the oil was not being returned to the frame.
Confused, I removed the side casing, clutch and oil pump, now expecting pump failure. But after stripping the pump, I found that it is all fine, and all within service limits, the sump screen is clear and the check valve is free.
I have also blown through the tank return oil pipe on to a rag, and that was all clear too.

I have heard of other top end problems on this bike, and was wondering if anyone can shed some light on the cause of this failure or if this is a common problem?
My friend is now stuck, between rebuilding this motor, or scrapping the bike.

Thanks in advance, Mr. P

[AIRWOLF]

Knackered head's seem to be quite common, I had always presumed it was lack of oil/maintenance.
the high price of head's and cam/rocker gear on ebay would suggest plenty folk looking for bit's.
if the pump is ok, i have no suggestions other than ensuring all oilways are clear.
Keep us updated.