XBR500 Broken Camshaft

[guest1645]

Hi,
Have just bought a 'project' in form of XBR500 (35 years since my last bike). Thinking to make it a bit more cafe.
It was running but only on two valves. Left hand valves were permanently shut.
Have now got into it and found the camshaft neatly split in two. Question is whether I can save the Cyl Head and the rocker cover.
Is there actually suppposed to be a centre bearing for the Camshaft formed by the profile in the Head and the rocker cover?
The camshaft doesn't look as if it had a machined bearing surface. I don't think Al could have caused so much damage/wear to the CI.
I'm  a bit confused as which camshafts would fit. Does anybody know if an XR600 cam would fit? Would it slot into existing cover or need the rockers and cover from XR600?
Really like the huge range of help that there is in this forum. Many thanks

[guest1645]

Hi, Here is picture of my broken cam. From pictures of a new shaft it seems that there should be a centre journal bearing running on the Al of the head. I can't believe that the Al has completely worn away the CI journal.  There is some CI deposited into the Head and cover bearing seats, but no where near enough metal to account for the volume of worn metal. It's not in the sump or oil filter either!
Has somebody machined away the journal in the hope that the end bearings will be sufficient? Any body heard of this being done before? Rest of Cam and chain and sprocket etc in really good nick.
Guess I have to find spare head and rocker cover

Regards
David

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[guest833]

I know bogger all about inside an xbr engine but I do know Kent cams do an xbr camshaft. Google it you should get somewhere
cheers, john

[JOOLZ]

I have never seen a cam fail like that before, and I have worked on hundreds of engines

[guest564]

There definitely should be a machined centre bearing, its been a while since I've been inside an XBR head but I wonder if the oil hole in the cam was blocked, I'm pretty sure that there should be one.
Kent do a regrind, you need to supply the core.

[guest1645]

Yes, fracture is neatly through the oil hole where the centre journal should be. Maybe it ran dry for a while as other posts here mention how critical XBR is for Oil level and changes. I am more and more convinced that someone has machined the journal away to clear damaged bearing surfaces in the head and cover. Cam has not survived as long as they hoped. Or maybe it did as I still bought it!
I can get a decent looking secondhand shaft here in Germany for about 50Euro. I'm just not sure yet ref merits of bulding up/re-machining the head bearing housing or getting replacement head cover etc.