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450/500T Startup

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taysidedragon:

--- Quote from: Skoti on January 27, 2021, 10:45:04 AM ---Gareth,

I'm don't know those engines either, but would the 'oil flow conveyor, exhaust camshaft'  pictured earlier in this thread be the answer?

--- End quote ---

Yep. I didn't see that. 🙄

K2-K6:
Yes I can see what I've written is a bit clunky  :) if I separate out the above to give each element clear air.

Common to all camshaft and follower surfaces,  the gap when not lifting is THE most crucial aspect of lubrication as it takes oil round the cam and refreshes the oil film on the rocker surface ready for the next load phase as it comes to lift the valve.  Losing that clearance will usually destroy any cam and lifter arrangements.

If the design of the valve train is very concise such that it stays, when set, extremely accurate, then this part of the train is unlikely to change it's clearance.

Valve sealing face along with the valve seat (particularly after rebuilding) are the area that will ordinarily show the most change during use.  This effectively moves the valve into the head and closes the gap set by the tappet.  Ultimately this compromises the oil film as above, and usually unheared in running. Setting the initial gap to the largest tolerance and very carefully checking at intervals will avoid this scenario.  My reference to Jensen is because he has recognized and recorded this process through his building and running these engines to a very highly resolved level.  The valve clearances very slowly close until it seems they are fully established, then staying fairly constant over more miles.

I think it's a foible that we usually respond to valve clatter in the desire to go and check clearance, but the obove is the real risk and will pass completely unheard, until something obvious fails.

Hopefully this expansion makes clearer than original.

SeanFD:
Ah!

Got it now thanks. And I can now see the reasoning behind the thought that more wear/damage will occur during running than at start up.

However the start-up theory would seem to explain the greater wear on the left lobe/follower, though not, to me at any rate, why the exhaust suffers more than the inlet.

MrDavo:
I’ve seen CB 450/500 based race bikes with an oil feed straight from the oil filter cover to the top end.

Not pretty but you can see why they do it, it shortcuts what’s just a longwinded route for oil that feeds the top end. On the other hand, a race bike is all about going full bananas when everything’s hot, rather than worry about what happens when you start from cold, so did they just find the feed inadequate?

Edit: I found an example, albeit the feed goes via an oil cooler, including back in to the bottom end.

royhall:
Any idea what feeds the left hand side in that photo?

My experience with the oil system on these engines is problems with the oil pump. On the K0 engine there is no way to tell what the oil pressure is (or isn't) as no red warning light exists nor a pressure gauge or even a simple button as per a Triumph. When building mine I managed to get hold of a NOS K0 oil pump, at the time I also had 3 used items. The new pump was fairly tight tolerences and quite stiff to move whereas the 3 used pumps were loose and sloppy. As it's a recipricating pump that sloppiness will loose pump pressure. Fitting the later model pump on an early engine does not work as the piston is a larger diameter which effectively moves the operating arm over by half the diameter difference. It will fit but the offset applies sideways force to the piston and wears it out.

After building my engine I filled it with oil and ran it with the starter motor on the bench with the cam covers off and plugs out. It took a while on the very first run to fill the centrifugal filter and oil galleries. All runs after that produced a good supply of oil which arrived at the inlet cam within seconds with oil at the exhast cam a few seconds later. I wish I could compare those bench runs to an engine with an old sloppy pump fitted. I think the pump is at least the partial culprit here. A pressure gauge would be an ideal defense.

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