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Life of Hi........................Vo

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K2-K6:
To add, most (well all really) road vehicles have built in "lash" between engine and gearbox as they are quenching the peaks of crankshaft speed oscillations to prevent them hammering the onward drive components. Hugely helps to take out noise and vibrations rather than amplifying them.

Generally it'll be at the clutch, with things like current diesel engines using dual mass flywheel in which one of the functions is to allow the crankshaft something like 120 degrees rotation freedom ( contained by springs) to filter out the chunky bits of torque at low rpm and make them sound more sophisticated than crankshaft pulses would allow. 

Seabeowner:
Same chain of course on the Kwaka 550s and they were using it without a tensioner into the 90s. But GPX600R has an upper and a spring loaded lower "guide", uses the same chain and handles considerably more power with no (or less) flapping around.

K2-K6:

--- Quote from: Seabeowner on March 22, 2021, 06:41:02 PM ---Same chain of course on the Kwaka 550s and they were using it without a tensioner into the 90s. But GPX600R has an upper and a spring loaded lower "guide", uses the same chain and handles considerably more power with no (or less) flapping around.

--- End quote ---

Yes, it appears to draw the very same observation in that use, rarely if ever breaking, not liking the "clanking" when idling after reasonable mileage and reluctance by owner to accepted it as normal to split the engine to change it. Also looks like the Kawasaki engineering dept had a good look at the Honda when planning theirs.

The "tensioners" appear to be aimed at addressing noise/quietness once worn here to.  With the tensioner effectively ejected once under high torque loading, it wouldn't seem to be able to significantly change wear rate.

K2-K6:
While looking at them for a different application it became clear that they are sensitive to oil viscosity.  Original development and oil range has requirements of 5 viscosity ATF with maximum of 20, making them effectively used out of range for this application. 

It specifically relates to how the oil travels through the plates to reach the loaded pivot surfaces.  Too high viscosity and throughput of oil is insufficient to keep the oil from having it's protection breached. In other words, it stays at load site too long to be reasonably replenished at a rate that allows the oil to carry away the heat generated,  oil breaks down at extreme localized temperatures and fails to prevent metal to metal contact. It looks like this that results in the grey slurry.
In extreme cases,  the pins and chain links get so hot that the components can fail (not in the bike engines) with that laying at the outer limits and the condition we see between this and zero wear.
They are though hugely strong with failure in bikes unheard of realistically but contrast this area with how the drive faces and crank etc don't wear, and you can see how the pins lay the other side of a tolerable boundry for the same oil.

K2-K6:
Thinking about original development of the engine, you can see just why it was attractive to Honda. They are really quiet (often referred to as "silent" chain) with really compact dimensions for the torque they can carry, with the possibility of an assessment made to understand if they could use it within their engineering demands with that viscosity essentially out of range. Also cheap compared to a gear drive (one of Honda's favourite methods) in engineering terms.

We know the answer if that took place (it must have done during original conception) with the R&D phase looking to answer that fully.

I know it's conjecture,  but it could be things like continuous endurance running keeping oil temperature fairly at target (thinner viscosity at normal running temps) that gave lifing assessment better than we'd see with shorter runs and cooler ambient temperatures.  Whether any significant cold climate testing would have taken place we don't know,  likely though that hot weather testing would be fairly extensive given their market scope. Higher ambient may disguise this particular wear site with oil able to flush through the link plates more efficiently. 

It seems their philosophy would preclude these bikes lasting so long,  which of course affect decisions made as to suitability for sale.  Always heading for the "new" with interest on future development, it probably surprises them that so many are still being used.

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