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Later Alloy Body Oil Pump in K0 Bomber

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K2-K6:
No criticism from me Roy. On the contrary,  I feel your assessment is near as identical to how I was thinking.

The general consensus in many things is that "more" is always better. This view very often fails to comprehensively consider subtle intricacies in the original design that have an impact that is completely missed in a very simple and basic decision to change something/anything,  in the vague hope that it may be better.

The most obvious consideration missed is that the cam lobe (which is the concern here) is absolutely not pressure fed. The cam on the rocker follower is completely at zero oil pressure. It follows that increased oil pressure cannot change this. Oil volume is different from pressure, interelated in a engine,  yes. But not the same thing.

Be interesting to see if a comprehensive mod list turns up,  but it may not make clear why it's done.

As you've already stated, and it looks to me too, that the original issues arise from how it's maintained. That tappet clearance is probably the most vital of most engines we'll see on here given the spring loading it must use to get a valve of that size safely above 10,000rpm,  with some space above that for safety margin. 

Nigel.

hairygit:
Similar discussions take place on the C90 club forum, especially with the guys that race them (Yes, they really do have proper races for C90's!) It is recommended to fit a TRX90 oil pump, but it is ONLY advantageous IF the oilways in the crankcases, barrel and head are enlarged from 1.2mm (Stock) to 2mm, not a job for the average owner, but it certainly helps things stay cooler with a higher oil flow.

jensen:
Hi,

The difference between the pumped volume of an early steel pump and a later alloy pump is moderate. In theory 30% more oil, in practice lower due to different issue's. One of the advantages is that more volume reaches the cams faster when started cold, and to me, that's the only major advantage (without changing anything else to the engine).

I have build another CB450 K0 engine with the later pump, but I changed a few things to the engine. When looking closely to the differences between the K0 and the K3 engine cases, one will see the differences in diameter of the 2 orifices located at the engine case toward the cylinder studs, and that's exactly what I did to the CB450 K0 cases, enlarge the diameter of these orifices.


--- Quote ---The most obvious consideration missed is that the cam lobe (which is the concern here) is absolutely not pressure fed. The cam on the rocker follower is completely at zero oil pressure. It follows that increased oil pressure cannot change this. Oil volume is different from pressure, interelated in a engine,  yes. But not the same thing
--- End quote ---

I couldn't agree more, and a later alloy pump does exactly that, adding more volume to the system, but without the proper changes to the engine, it's a waste of energy due to higher pressure in the system. This is why I wanted to do a test with another type of oil, a type of oil which has a very strong layer that won't break, even under extreme conditions (both, temperature and pressure).


--- Quote ---As you've already stated, and it looks to me too, that the original issues arise from how it's maintained. That tappet clearance is probably the most vital of most engines we'll see on here given the spring loading it must use to get a valve of that size safely above 10,000rpm,  with some space above that for safety margin.
--- End quote ---

I partly disagree on that, however, in many cases you are absolutely right. I also think it's the nature of the torsion bar setup, the cold start issue's and some design errors Honda made during the development of these (early) engines.


--- Quote ---this perceived exhaust cam problem has its roots in lack of oil changes and generally poor maintenance
--- End quote ---

No, I'm sure it's due to the poor design and magnified due to not warming the bike up properly. Honda was aware of this problem and solved it in the later engines. Honda has a history of poor design oil and lubrication issue's over the years (remember the first V4's engines).


--- Quote ---After all, Honda spent millions back then developing this highly sophisticated engine
--- End quote ---

That doesn't mean that no mistakes where made. Today, car and motorcycle manufacturers spend even more money and effort on development, and despite all the experience and know-how, issue's arise from time to time.


--- Quote ---If anybody could supply me with a complete list of the changes that were made by Honda at the time of the oil pump replacement I would love to upgrade the Bomber, but without that I see no point. Sorry.
--- End quote ---

I don't think anyone will do that, since not many people measure and test things, and publish the outcome. They just searching the internet and are asking to be convinced by others ;)

I do ride my CB450 K0 on highways for longer periods, I do ride the bike as it should. I found issue's of the left exhaust cam, and yes, I replaced the oil every 1000 mls, and warmed up the bike before taking off. When I'm at classic events, most people unload there bikes from their vans or trailers. And when I ride with a CB450 club, highways are avoided and the average speed is lower then 40 mls an hour. Remember, the CB450 K0 is a supersport bike, not a tourer. Maybe a good read is this thread : http://www.hondatwins.net/forums/55-engine-discussion/4922-cb450-k0-dyno-run-why-doesn-t-need-five-speed-trans.html

Conclusion ?

No, it's not needed to add more oil pressure or volume in these engines when using them in a normal way. Warm it up carefully and maintain the bike and you're more or less ok. Some cam wear will be your share, but one will hardly notice since most people don't add enough miles to the odometer in their live.

I tried to solve it in an other way, using a better oil, an oil which has a stronger layer and doesn't give up at higher temperatures and pressures. Until today, this seems to be a good route, until someone proves otherwise, based on severe testing and  publishing results.

Jensen

AshimotoK0:
Went to get the NOS oil pump today but no sign of any Service Bulletins from where it originated. My guess would be that it would have been an upgrade part as everything else I got from him has been upgrade parts for 60's Hondas. I need to get the oil pump which came out of my Bomber engine though to compare to it.
Meanwhile, here is £40's worth of NOS one.

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jensen:
Hi,

This the later version, there are 3 versions, the pictured one is the latest style early steel pump. The best also....

Jensen

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