SOHC.co.uk Forums > CB500/550

Cam shaft and rocker arm wear?

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murdock:
Ok , lo miraré de nuevo cuando encuentre mis gafas

Ok, I will look again when I find my glasses, where are they when they are not on my head? 

K2-K6:
It's the "strakes" ( the lines going in direction of cam travel)marking the rocker faces I'd be most concerned about, which is what they look like in the photos. 

Ordinarily to wear the cam lobes you get pickup (lubrication failure under pressure) that cold welds one surface to another, this then acts as abrasive (on the rocker face) to wear the cam lobe as it goes round. It can also leave no tappet clearance at that point, which further destroys the oil film right the way round the cycle in that line. This is why it starts to leave that characteristic strake.

Ultimate cause is oil condition/quality, usually through fuel dilution as it's been run too long between changes.

K2-K6:

--- Quote from: Oddjob on February 09, 2022, 08:39:10 PM ---Phil, just say you want 5 degrees more overlap and 10 degrees more duration and let them worry about it. It's the way the lobes are profiled, overlap is the time both valves are open at the same time, duration is the time the camshaft holds the valve open.

According to Mark it really wakes up the 500/550 engine, there are other little things you can do like making a pocket above the inlet valve, they always say "Don't lower the floor, raise the roof", and raise the exhaust ports about 2-3mm and smooth the port out. That's to aid the flow of exhaust gases as they exit the engine.

--- End quote ---

Thinking about this and follower geometry. It looks as though you could do this with a rocker geometry change, in that if you have the rocker pads refaced (Newman cams) and ground to a larger radius, then it would achieve the above overlap and duration with the std camshaft. You could swap them out to see what you preferred then.

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