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Cb750 Clutch rattle

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K2-K6:
Definitely see your point of view Roy.

For posterity on forum, its worthwhile noting that there's not a mechanical cure for it. The clutch pack "adaptions" primarily focused on torque take up as the clutch is released. When it's closed, effectively one rotating unit that has no means of rattling.

The cush drives, in any clutch, are for frequency buffering to stop crank pulses being a problem as they go down the transmission line. Loose though will contribute to this effect in system rattling, although not specifically designed to cure or mitigate while sitting there at idle.

Yes, the original design of chain (obviously very early in mass produced 4 cylinder design ) is quite crude and with rudimentary "tensioner" that has no damping action at all. The origin though still comes back to crankshaft giving lumpy delivery when sitting idling.

Years ago, talking to a builder of these for sidecar competition, he explained that they had really short chain life in typical use as the change down engine braking (to alter the outfit attitude in steering) really caned the chain, particularly as it effectively pushes the wheel out from tension on that "slack" side of chain run, to then leave the top (normally pulled tight) run flapping like a flag.  His experience was, if left too long the chain would override the sprocket teeth and snap under hard use.
Also why cam chain systems have a curved tension side, and adjusted guide opposite on return run of chain.

Of course they went to hyvo for 350/400/500 as they effectively run with very low slack that could amplify oscillation potential.

Honda actually modified the primary drive in last iteration of this bottom end too. The RCB endurance racer was this bottom end with bespoke twin cam 16v head, in which they converted to gear primary, with a idler intermediary gear to correct the drive direction when going from chain to gear pair. You can see they came across limitations here, that led to further development in producing next generation of road going twin cam tbat came next. Acknowledging your observation here effectively.

Laverda Dave:
What a great explanation Nigel especially with the racing history to give it a bit more context.
Thats why I love my VFR, no chains flapping around (apart from the rear drive chain!).

K2-K6:
Yes, definitely a very high water mark in Honda history those gear-cam V4  sounding absolutely fabulous too.

Good you got to keep your one Dave what with the U lez scare etc.

Speaking to a local accredited tester for that scheme, they tell me that virtually all bikes tested from before emissions classification will generally pass. The critical limit was never a problem for that era as they don't ordinarily run lean/hot with other exhaust gas treatment not fitted. They were, of course not classified as routine although that would have qualified as below limits anyway.

Laverda Dave:
Mine failed on the first attempt Nigel (and it is PFI not carbs so I expected it to pass). It failed on a closed throttle after an acceleration run, the injectors squirt fuel into the engine on the overrun as they are designed to do, the fuel didn't fully burn and it was 0.1 over the limit! The tester (an ex racer in Stevenage where I got it tested) used his laptop to remap the injector sand put a bit of redex in the tank in order to solve it and I got a pass following another run on the dyno.
The tester said the TfL dyno programme they have to run the bike to requires the bike to accelerate from very slow speed up to 40mph for a few minutes and then back down to virtually walking pace. It’s all utter pants, show me anywhere in London where you can travel at 40mph for a few minutes especially considering everywhere is LTN's, camera's and traffic jams!
It is all a big money making scam by our wonderful Mayor.

K2-K6:
I recall the overall experience of testing, and ultimately successful outcome Dave.  Thought it was very good you've been able to keep such a nice bike that's been cared for so well.

Thats a cute adaption used though, tbe redox dosing   :) it may have cleaning effects, but just as importantly it'll lower combustion temperature (a key driver of the output) by being non available to burn in petrol combustion, illustrated by smoke usually.  It should keep combustion temp down a little by not contributing to burn load for each stroke its used. This to help meet the demand of certain measured parameters.

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