Cam galling

[Crazcnuk]

Hi there, have my head out and apart, was looking at the cams.

On both the exhaust and intakes, cap #4 and 5, there is a fair amount of galling. There is obvious aluminum pickup on the cam on both the head and the bearing cap.

How serious is this, and can it be fixed?

[mro]

Can be very serious

(Standard)
Camshaft to cap clearance 0.20 ~ 0.054 mm (0.0008 ~ 0.0021)

(Maximum) 0.160 mm (0.006 in)

Can use "plastigauge" to check

If exceeds clearance, can think of no reasonable way to fix.

Unlikley for cam to be worn but can measure to be sure.......
Camshaft bearing surface diameter 24.967 ~ 24.980 mm (0.9830 ~ 0.9835 in)
_________________________
If out a spec and noticeable marks on cam, would replace both head and cams.



mro

[prometheus578]

As MRO said, use plastigauge to see it the clearances are still within spec. Now, I don't know just how badly stuff is chewed up. Galling could be caused by insuffient lubrication, or you may be looking at what happens when a piece of hard crap gets into the oil and forced between the cam and the bearing surface.
If the clearance is out of spec, you're looking at money. If it's just gouges caused by grit, clean up everything and rive onward. there's still plenty of good bearing surface left for the cam to ride in. Again, this depends on what the plastigauge tells you, and just how chewed up everything is.
Not sure about XS's, but on most machines, seeing how the cam caps are placed on the head and then the holes for the cam are drilled through them, cam caps and head are a matched set, and one really can't just replace one cap, but should buy a new head with it's 'custom fitted' cut caps.
Of course... we of the 'Low Buck Club" would just scavenge a cap offa a spare head, plastiguage it to make sure things look Hunky Dory, and slap it in and run another twenty thousand miles or so. (This... after figgering out what happened in the first place)

[Crazcnuk]

Well, normally the way this type of bore is fixed is to mill some material off the caps then align bore the whole thing from one end to the other, which is probably why the head has those half moon holes next to the end of the cams. Just not sure how hard it is to get they head to fit on a milling machine...

The galling on this one looks like it was getting a little starved for oil and it started 'pulling' aluminum around the cam.

I have the other head to check out, but it has a broken exhaust stud...

[andreashweiss]

I have some 81 cam caps in my parts pile and both intake exhaust cams for the caps.If you need something let me know They came out of a cylinder head that had really bad road rash and it looked awful so I stripped the head of useable parts. Valves/springs already gone, andreashweiss@yahoo.com

[mro]

normally the way

If you have your own equipment or a buddy does, would try to line bore cam journal, then weld/grind cam to fit.. Would/could be XSive if had to pay a shop to do.


mro

[Crazcnuk]

I think the cam(s) are fine, the aluminum will likely just come off with a polish. It's just how much one can take out of the bore, to align bore the journals, as this will drop the cams ever so slightly lower in the head.

My head repair guy will likely be able to tell me more on this as we get further into the repair.

[mro]

Wonder what effect to oil pressure/distribution if cam journals a few thousandths too big


mro

[Crazcnuk]

the idea, when you align bore is to bring the clearances back to spec, but in doing so you end up moving the bore slighlty to the block side, or in this case, the head side.

Only other way I can think to fix it would be to find a caged needle bearing that is close and machine to fit, but that would be a lot more work.

[2fast]

Stupid question..........
What is the aluminum coming from?

[Crazcnuk]

The bores that the cam(s) ride in, #4 and 5, left side of the engine when your sitting on the bike.

I assume at some point the engine starved for oil at the top end and these are the last place oil gets to? I am also assuming the head is made of aluminum.

Since there is no bearing used in the bore, when no oil gets there the steel cams start to pick up aluminum from the head.

[2fast]

Doh!! (Hand slapping forehead)........
I was thinking it was on the cam lobes.......