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Zinc content in oil

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Bryanj:
When i worked for Frazer in Glos we used to buy Filtrate 10w40 in 5 gall drums from the Suzuki dealer in Bristol (Used to sell pushbikes as well) as he bought it by the truck lload and it made it cheaper than anybody elses for shop use and met Honda specs. Dont remember any collodial graphite in it though

K2-K6:
I think there are, as you say Bryan, two distinct parts to that story as filtrate. The normal oil that the brand name applied to and the colloidal graphite stand which may have been incorporated into the oil in earlier years or added as a package to any oil from a separate can to, in effect, dose your oil of choice.
I guess that with the advent of more complete filtering systems the days of adding something of that partical size to engine oil would largely disappear. As Ash found out then,  it will all end up in the filter system.

There was an interesting documentary last year on the graphite industry centred around Whitehaven in Cumbria,  as they found that molds for cannonballs when coated with it enabled a particularly clean release of the cast balls. This allowed them to be made much closer to consistently spherical,  this along with then allowing a much more accurate choke in the canon barrels vastly improved our naval warfare capabilites with the attendant outgunning of opposition.

More relating to the bikes on this forum, I don't consider anything ( certainly within the 4 cylinder bikes) mechanical to give the oil a hard time resulting in oil condition deteriorating to the point that it would be considered unable to lubricate properly.
That doesn't mean that something else is not in operation that does.

K2-K6:
To move on from the mechanical effects imposed on the oil in these bikes, I feel it's the combustion strategy that causes the oil life to be quite short.

There's a basic problem running multiple slide carbs to fuel these engines. I can taken a guess as to why the design originated, Honda's mimic of their sixties race bike technologies leveraged, in marketing terms,  to deliver road versions of that track success.  Pretty good it is too.

With one carb per cylinder there is no air volume passed through that carb except for its own cylinder, obviously,  so the vacuum can't be moderated as perhaps a single carb for multi cylinder would. In addition, a simple slide carb has what I'd consider to be "symmetrical " fuel metering in that it's a straight correlation of air vacuum to the amount the main jet is allowed to flow by it and it's needle geometry.
This is where it gets more interesting. For complete burn of fuel you need an ideal ratio of 14.7 parts air to 1 part fuel ( think that's right)  and which is known as the stoichiometric ratio. If you don't run this, and many engines don't, then any excess fuel is not burnt which leaves it to go out of the exhaust port or past the rings into the oil.
The specific problem with slide carbs as fitted to many of these bikes is that to get the engine to accelerate well then you may need to get down toward 11  to 1 ratio to light it up and make it respond fast to the throttle being opened,  and if you jet it like that it'll have to run at that ratio even without load, ie trickling along on part throttle. I think it's worse than that though, to get the mixture rich enough to respond well is also tempered by the transient characteristics of this carburettor arrangement. If the engine is running slower revs and you open the throttles wide instantly then the vacuum drops as the carb is wide open and the engine is not sucking much. Sooooo, you have to in effect compensate for this small part it time by using an even greater supply of fuel if you want it to really jump in rpm. All of which can't be mitigated for steady state cruising. In other words they run constantly too rich from theoretical stoichiometric by quite a long way. And also why PD carbs offer something of a solution in adding fuel just for the acceleration phase and allowing more moderate cruising to be accomplished at something toward a normal fuel air ratio. In this sense they are simply better for the engine and a blueprint (a crude one)  for modern fuel injection systems. In other words, asymmetric fueling based on engine load and response requirements.
Interestingly the CV carbs do something similar. I'm guessing again that Honda didn't want to use these for their first fours as they may not have been considered sporting enough / or offer the level of response the design team asked of their project. When you open the throttle on CV carbs, the butterfly controls demand from rider and in response the slide is raised via engine vacuum so aiming to avoid the transient vacuum loss you get on slides when you walk the throttle wide, aka Constant Vacuum. They also go further as I understand it in that the slides are usually damped going open so that when the engine vacuum s rising the slides lag behind this curve,  this momentarily causes a higher vacuum peak just under the slide which pulls more fuel in to give a richer mixture just when needed and until the slide position catches up with engine vacuum. You could view the throttle butterfly as a request system that allows the engine cylinder vacuum to be allowed past and influence the slides which then accelerate the engine.

The CV types are useful as a comparison to the slide type carbs but also have relevance to the original question about the 450 CB.

So in realty on the fours,  I think the oil is prematurely trashed by not being able to run a more optimal mixture. They are far more orientated toward race engine running than just cruising about.

Green1:
I'm to tiered too read this at the moment but from what I understand wasted fuel gets into the oil thus fecking it up.

I do wonder how long modern Diesel engines will last with DPF's.
If there stopped half way through there regen they dump the unburnt Diesel into the sump.

hairygit:
But diesel IS oil, albeit of a very thin nature, check the V5 of a diesel vehicle, for fuel type it states "Heavy oil".

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