SOHC.co.uk Forums > CB500/550

What would cause this camshaft damage?

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Seabeowner:
Is that wear or just crappy metal? Is it on the nose of the cam?

K2-K6:
The wear (looks like lobe peak ? ) is from failure of the oil film at that site, resulting in effectively cold welding parts of the camshaft surface to it's paired rocker.
This either through fuel diluted oil or too long between changes (same end result really) that then doesn't prevent metal to metal contact.

Thats from oil quality failure.

Another contributor is to run with the tappet clearance too tight, which prevents the oil film from being established on the lobe ( many cams are simply lubricated by this "dipping" method. It leads to oil failure local to just that site, can be just on one lobe and follower pair.

If all or most are affected, then more likely just oil failure overall unless all of the tappet were too tight.  Should show some residual effects on rocker if exhamined closely.

Oil filtration plays no real part in this process, just tries to stop debris from this site spreading throughout the engine by embedding into soft locations like crank bearing or camshaft main bearing surfaces. If those camshaft bearing are ok, then it looks like the filter caught the chunky bits. After going through the oil pump  :)

Use Grapphogen product on installation of new camshaft to avoid initial risk.

Oddjob:

--- Quote from: SteveW on October 22, 2023, 06:21:58 PM ---Luckily I already have a replacement cam to go in. I’m going to stick a CB650 cam in, supposed to be a good mod for a little bit more power.

--- End quote ---

The re-profile of the old cam will match the profiles of the 650 cam but without the problems fitting the 650 will cause.

With the tacho drive gear on the 650 cam being different the tacho will read fast. Why have that?

SteveW:
I have the 650 drive gear and a 650 tacho so hopefully all good to go.

Oddjob:
No, you don't understand. The drive is geared differently from the 500/550 one, so it spins faster at the same revs. So the tacho reads fast, instead of it saying 2000 for instance it may say 3500.

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