Cam carrier damage.

[AshimotoK0]

The Classic Bike article is  in association with DSS so I will ask him if he has a direct email contact with the person who's handling the resto. (Rick Partington). He may then give us more information on the conversion or indeed if they are retaining the modified head (don't know when the next issue is out, the September issue dealt with grinding/polishing the crank journals, which I always thought was a big NoNo but to be fair I think it may have been intense polishing rather than any form of  grinding ... Not going to argue anyway with the guy from Modus Engineering  as he looks like he can handle himself !  ) Perhaps Rick would join us on here?

Leave it with me.

Cheers ... AshD

DONE  !!!!!!!!!!!!!!

Hello David,

In the CB mag article in association with yourselves on the 400/4 restoration, they discovered that the project, bike had Kawasaki cam bearing shells fitted. I guess these may be from the Z900 as the smaller KZ fours had bearings directly into the alloy,I believe (The  KZ650B1 I once owned definitely did not have cam bearing shells). We have had a discussion on this, as part of a thread on SOHC.co.uk , recently. Do you think Rick Partington would share any more information on the bearing conversion (photos etc.) or indeed join us on SOHC.co.uk ?  Or if he prefers he could email me direct and I can pass anything onto the forum, as I tend to do with yourselves.

Link to the thread:

http://www.sohc.co.uk/index.php/topic,7175.0.html

Best regards .... Ash

[bike-pusher]

I don't think Roy Hall's analysis is necessarily true.

For a start, Honda had quite a lot of experience in building small engines whose cams didn't use separate bearings (CB72/77 series apart).

Secondly, while plain crank bearings and big ends are indeed cheaper than roller, it's not as if this was unproven tech.  As regards plain primary chains, everyone used them in the 1960s and they worked fine.  The fact that you can't lift the cam cover with the engine in the frame isn't indicative of a cost-cutting measure - it's much more likely to be that the frame guys didn't talk to the engine guys until it was too late. 

The fact that CB750s and the like are still running after 40 years shows that the design really was over-engineered. 

What has killed so many SOHC Hondas has been simple neglect.  There are people even today who regard recommended service intervals with disdain.  Back in the 1960s, the idea that you absolutely had to change the oil every 3,000 miles (or whatever) rather than simply "when it got dirty" was hard for many to accept.  But if the bikes are really maintained exactly as per factory recommendations, they last an incredibly long time.

[AshimotoK0]

I agree Neil .. and I reckon it's worse with USA bikes. You see really low mileage twins (sub 10k miles) with pitted cams/rockers, scored cam bearings. Anyway Honda had about 9 years to change the cam carriers on the 750's and they basically remained the same apart from a minor change on the K0. Kawasaki were basically pipped to the post on a 4-cyl bike by the CB750 and scrapped their original plans. I have never seen a Honda bike with replaceable con rod little end bearings but not saying they don't exist. The only bad thing that Honda did was not making the cush drive rubbers in the primary drive replaceable by designing  a rivetted together assembly. A German forum actually repro'd the rubber cylinders but refused to sell them outside of the forum. I have a couple of the rubbers taken from a nearly NOS primary drive sent to me by the guy from M2 racing, with a view to getting them analysed/hardness tested and repro'd by a guy in Hull, but it went onto the back burner when I wasn't feeling so good.

Cheers ..Ash

[royhall]

Sorry if my comments ruffled a few feathers, forgot it was a Honda forum. LOL.  However the as I stated earlier the design brief for the CB was to be as cheap as the triumph. Simple maths dictates that you cannot build an OHC four with electric start and all the modern stuff for the same price as a pushrod twin without making some compromises. An example of that is the cam carrier ie. the oil hole is direct onto the cam with only a thou or two clearance for any debris coming down the line to get through, this results in the blockages and cam trashing. Surely a radial slot around the centre of the journal about 20 thou deep (like a big end bearing) would allow somewhere for the debris to go so it does not block the oilway. Cant be that hard, can it? Remember also that the CB and Z1 launches were only 3 years apart which really makes them the same era.

[Bryanj]

Biggest problem with the fours was old mechanics used to British bikes not being super clean when rebuilding----surfaces have to be mirror finish; NO excess of gasket goo and all oil paths blown through

[Bitsa (Ralph Wright - RIP)]

With Bryan on this one.I have some guys over here with brit bikes who still say if you see an oil leak you have no worries not the way I carry on
Cheers
Bitsa

[K2-K6]

I completely agree with both last posts, Bryan is right that you have to be impecably clean to make sure you introduce no contaminants during building these motors up and then you should get no material to block the oil supply. The oil pump is sucking in through a stainer and then supplying through a good filter as well, so any bits that are in the oil gallerys are usually there by some other route.
Bitsa's oil change and filter schedule (on another thread here) also has an important impact in that if you leave the filter to get too restrictive then the oil will still be supplied to the motor via the pressure relief valve built into the filter housing bolt and so bypass filtration.
I'd challenge the statement about making the cam bearings down to a price and therefore they are in some way sub-standard design also. Some of the very best fourstroke heads run cams straight into the alloy as Honda do (on the 750 they made them replaceable as well so the head is not scrap in the event of failure) the tolerancing can be better with less components also. I don't think you get anything wrong with them if run to the right requirements.

[Woodside]

As much as I hate to think any of our hondas were slung together on a budget...
Is it possible the engineers and accountants had a meeting that went...
Acc..."We need to save money on the cam journals"
Mech..."but if we do that they will need to change the oil every 3000 miles?"
Acc..."ok sounds good..stick it in the manual"

[Bitsa (Ralph Wright - RIP)]

K2 K6
I only stick to my oil and filter change because she only gets short runs I mean 20 30 miles tops 1000 miles a year if lucky ok Oddjob I think or was it hairygit cant remember?I do remember from somewhere thats its the short runs that kills the oil.
Cheers
Bitsa

[hairygit]

Yep, short runs are very harmful to the engine oil, as all engines produce moisture internally, and on a short run, it doesn't get a chance to be evaporated off by the heat of the engine. Also the same reason the incredibly expensive standard exhaust pipes rot out, the moisture from the combustion air doesn't get the chance to boil away, leaving a nasty acidic slurry liquid in those oh so costly silencers, while the tin worm has a feast on your exhaust innards until your next short ride out. The best policy is to make sure the engine gets thoroughly hot, or change your oil very frequently, although that WONT save your pipes from rotting, only a good hard ride will do that!

[Green1]

Long runs don't clear the moisture from 341's.I recently went to Bury St Edmund's and back a total of 107 miles
The bike looked a bit rough after so I took the pipes of to clean them when I placed them on there ends quit a large puddle appeared on the floor.
I'm now wondering if squirting WD40 in the drain holes will help displace  the water.
Mick 

[Bitsa (Ralph Wright - RIP)]

Agreed, each winter squirt shed loads of some marine preserver down them runs out all the holes but so far 5 years and still mint
Cheers
Bitsa

[K2-K6]

I know what you mean Bitsa, if they get hot enough then they should easily make the spec in the manual for mileage between changes.
Also as hairygit says, the biggest change to the oil is contamination from unburnt combustion. It's funny that there is usually so much argument over what oil to use on forums when that probably matters nothing like as much as condition i.e. if you take any oil of your choice and dilute it with water, unburnt fuel and whatever else leaks past the compression ring, then all of the best choices will be left with naff all protection for the motor.
One of the bisggest differences of modern petrol motors ( cars in particular) is that they run sooo lean with big enrichment only when absolutely needed and when it gets burnt during max acceleration. These old style carbs can only be best set to give a good throttle response when you need it and the light running really has to take care of itself, hence alot of unburnt fuel components just condense inside the exhaust, which is what you are seeing Mick.
Come to that Mick it might be worth dropping your needles one notch and giving a couple of degrees more advance on static timing to see if you can get the combustion temp higher, then check the plugs to see if they are not getting out of their heat range.
Maybe worth getting an emissions reading before and after to see what change you get, should be looking at HC ( unburnt hydrocarbon) content I guess.
Bit off topic I suppose but also relevant to cam bearing life.
Nigel.

[bike-pusher]

Roy - you're still wrong.  In fact, politely, you're talking nonsense with this quote:-

"Simple maths dictates that you cannot build an OHC four with electric start and all the modern stuff for the same price as a pushrod twin without making some compromises".

The answer is: yes, you can, if you have sufficient automation and the right tooling and manufacturing processes, and also economies of scale.  The archaic British industry of the day certainly couldn't, but the Japanese could.

You're also ignoring things like labour costs and exchange rates.  Japanese labour rates were way lower than ours in the early 1970s. One pound bought you nearly 800 yen in 1972.  Now it buys you just 177 yen.

In short, the Japanese production lines could produce bikes at lower cost than the British (or possibly anybody's).  The wages paid were also lower.  And their currency was cheap.

[royhall]

You know 'Bike Pusher' your probably right about the 'Simple maths' quote being nonsense.

Had recently read an article about the birth of the Superbike in an old American magazine where it compared various models such as the CB750/Z1/GT750 etc and that is what started my train of thought. The reasoning in that article of why it sold so much better than the competition was due to the cheap price. Apparently they not only matched the Triumphs price but beat it by a good margin.

But you know, they never mentioned your points about labour costs, exchange rates etc. The assertion from the article was that the CB was deliberately built down to a price point (maybe some degree of truth in that) but any successful product needs to hit a price target. And like I said earlier "As a corporate decision it was a master stroke that almost single handedly broke the British bike industry".

Have thought about that article for a while now, and read the comments on here, especially the comments about using tried and tested technology, Yes, I think I may have been wrong about the CB750, and that article was just full of biased bull**** There, said it. Isn't it cr** being wrong LOL.