Failed CB750 K Camshaft

[Hinomaru]

I posted this thread over on the SOHC - USA site, thought it might be interesting for the UK members to see another failed CB750 camshaft: 
 
http://forums.sohc4.net/index.php?topic=97063.0

[hairygit]

Nasty! I agree with lubrication failiure, but not so sure about the silicon theory, as the cam appears completely trashed along its entire length. The chances of silicone blocking ALL the oilways to the top of the engine seems a bit of a long shot to me. I'd be looking at pump failiure, or clogged filter, causing the bypass valve to open, and the resulting low pressure in the oilways as the oil heated up and thinned doing the damage What do you others think???

[K2-K6]

Clearly a lubrication "shortage" has happened, but how it came about is difficult to say without further inspection.

It looks like suspiciously low supply over a period of time and/or dilution by petrol could have got there. I've seen a new cam scrapped in less than 30mins running on a car with petrol diluted oil but the journals were intact.

I also thought what looks like burnt oil on some of the base circles (of the lobes) is very odd and suggests an over temperature situation.

I would never, never, EVER use silicone on these engines for any of the sealing sufaces.

[Bryanj]

Don't know about "Never ever" I've been building these Hondas since early 70's and used silicone since it came out BUT it has to be used sensibly and sparingly---I have also seen just as much trouble caused by Hylomar and most commonly simply not being clean enough on reassembly such that bits of old gasket get into the oilways

[UK Pete]

Threebond 1104 used thinly on the crancase halves is apparently what the bike manafacturers use , i also use this as it does not break loose like the squeezed out silicon on the inside of the cases
As for the worn out cam, it looks like someone has sabotaged it with a handfull fine sand ,
Pete