Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: royhall on September 20, 2014, 05:48:36 PM
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Hi. Just putting the top end back on an F2. Whilst cleaning all the parts and clearing out the oil drillings, I have found some damage to one of the journals on a cam carrier. The oil feed hole was partially blocked and that I assume was the cause. I have dressed the journal lightly with very fine wet & dry and there is definite scoring evident. How much damage can be safely accepted on this part, and if replacement is required would I have to replace both carriers and the cam? Cheers.
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Need some close up photos to see how bad it is or, how not bad it is.
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You can replace just one carrier if needed, as to repair way back when we had a man who bored out the carrier and madw bronze half bearings which were pegged to stop rotation
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Have included a photo, hope its clear enough. Its the journal on the right hand side, the end float journal. Have cleaned it up with very fine wet & dry (absolute minimum) and checked with engineers blue (full contact with just the scores not bluing). If you run your finger nail across it, fine scores can be felt. Made the decision earlier to go ahead and assemble the engine which is now done. The engine turns over with a socket very freely with nothing binding. All the oilways have been run through with a guitar string, carb cleaner jet, then compressed air. Fingers crossed it will be okay. The decision was made easier because there is a frame kit fitted to the bike, so I can strip the top end in situ. Hope its all okay though. What do you think? Cheer Roy.
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Hi
Have to say the inner is good but not happy with the outer if it were me change it.Whats the cam like?The same?
Cheers
Bitsa
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The cam is actually very good. But it would be as its much harder than the soft alloy, and its not picked up at all. Are these carriers still available new, as an eBay item may be no better than mine. If it needs changing now's the time I guess whilst its still on the bench. Cheers.
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Anybody got a good quality spare cam carrier with caps (12010-410-000) that they are willing to part with for some cash. Would be greatly appreciated. Thanks.
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What was that company that used to metal spray surfaces like that, and then machine them down?
Joy Engineering? Think they went bust. Must be someone else....
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Don't think you can metal spray alloy, how much clearance is there on the bearing--platigauge is probably the only way to be certain. I would be tempted to modify the clearance and run it, if you want to call me on 07795162623 any evening Sunday to Thursday incluse AFTER 8pm when i am at work I will give you some ideas. Don't with hold your number or i won't answer!
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Thanks Bryan will give you a ring Tuesday after 8pm. Cheers Roy.
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Bryan. Many thanks for your offer to help on my cam problem. I have this morning managed to find a good quality replacement carrier complete with caps on American eBay. And for the princely sum of £27 plus £29 P&P, a good price I think. So that will be going on as soon as it arrives, and hopefully problem solved. Thanks again for your help.
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You did well there, they are no longer available new, and when they were they went for silly money.
Cheers
Den
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Really hurts when the p+p costs more than the part! Also, you may get charged import duty, plus V.A.T. on the cost of the part AND the postage, then Royal Mail will charge a handling fee on top of that! :(
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Hairygit
You have hit the nail on the head there mate there some wicked bargains from the states but the post costs do not make them wicked anymore.So far so good for me not been hit with import duty yet but I am sure I will cop it soon.It seeems to work if you keep it to the old way IE duty free I keep it below 200 euros and touch wood OK.Used items don't seem to matter but new oh yeah.
Cheers
Bitsa
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Bitsa, it's £15.00 in Britain, anything more than that can attract import duty, plus 20% V.A.T. on original cost AND postage. I got caught out last year, my bargain front caliper for my 750F1 from the U.S. went from a £25+£10 post to nearly £70.00 by the time it arrived at my door >:( And 3 days after it arrived, D.S.S. had new replica bodies in stock for £49+V.A.T., typical!
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What was that company that used to metal spray surfaces like that, and then machine them down?
Joy Engineering? Think they went bust. Must be someone else....
Phill joy engineering
Still about and race tuning Hondas ....
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Yeah I am expecting a hit from import duty etc. The bottom line though is I just could not find a good used one anywhere else. There's a few on a Dutch breakers site but the caps are missing and as you know they are line bored so without the original caps they are just scrap. Are these things possible to repair at any sort of affordable price, because these will start to become a major headache for CB750 owners pretty soon. Back to the 1000 mile oil change regime I guess.
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I do have one of those used & spare somewhere but it's from an F1 I think or possibly a K7. I never sell anything on here I always give stuff away free, that I don't ever envisage using myself, but that's a part I can't really do for free as it cost me decent money and I was saving it for a 'rainy day'. No idea what one is worth. Any ideas you old sages on here or if it will fit the F2 model?
It may take a bit of finding too but I have definitely got one spare somewhere. The cap markings match those on the carrier, so no worries there.
Cheers . AshD
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Did a bit of research on that. Looks like its the same part number from the K2 to F2 but I guess there could have been a delta change during that amount of time, who knows. Taken a chance on the American eBay part as it looks identical and in good nick in the pictures. Seller says its good nick as well. If it turns out to be junk when it arrives, I would be happy to pay you for the part Ash, no problem. I know what you mean about a rainy day part though, these things are now rocking horse to find and its going to get worse as the used parts get used up. Did find a few new ones on the net (all America) but they were 250 dollars upwards. Hopfully some entrepreneur will jump in and re-manufacture.
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They can be repaired, you can still ring this evening if you want ideas
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In the Classic Bike 400/4 resto. article they found that a PO had used Kawasaki shell bearings for a damaged cam bearing head repair. Also at least on the CB750 they have 'carriers'. Decent of Kawasaki to fit shells to the cam, why couldn't Honda do that.. Don't know which model(s) though. Same thing with Honda little ends on con rods.
Cheers ... Ash
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love to know how they got the machining done as there is no hole to line bore
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The shells might have been crankshaft shells or big end shells from a smaller bike. I'd also like to know how they did it.
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The shells might have been crankshaft shells or big end shells from a smaller bike. I'd also like to know how they did it.
No I looked them up and they were cam shells. possibly like these.
http://www.ebay.com/itm/Kawasaki-Z1-Z900-Z1000-camshaft-bearing-shells-/331289806403
[attachimg=1]
Cheers...Ash
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Oh, right, from a Z1/900. Interesting, because I've had a number of Z550s/650s/750s and they didn't have separate shells.
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Oh, right, from a Z1/900. Interesting, because I've had a number of Z550s/650s/750s and they didn't have separate shells.
David from Saisei is a Z900 owner and confirms they have cam shells. I had a KZ650B1 and don't remember it having shells but I never stripped the engine. Bit like the CB750 has cam carriers but on the 500/550/400-4,350-4 the cam runs straight onto the alloy head/cam, cover. Interesting on the Classic Bike resto, someone had fitted shells into the the head but fitted a new cam cover without shells. Surprised that the 400/4 head and cam cover were not line bored as a matched pair. There again the 250/350K twin crankcases were not matched and were sold individually.
Cheers ... AshD
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Have to say like that idea kawaski did but in all my time never seen it
Cheers
Bitsa
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Have to say like that idea kawaski did but in all my time never seen it
Cheers
Bitsa
Let the Good Times Roll !! :) Those shells look like they are nine quid each but how much would a head and cover be ! I seem to remember the CB72 had ball races for the cam bearings. Then the 250K had plain bearing 'covers' as did the CB160/CB175/CD175 then the CB750 with carriers then the dreaded smaller fours with cam running directly in the head. Think the 250G5 was like this too. Not sure about the CB500/4 as I never owned one, which is a real shame.
Cheers .. AshD
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the CB500-4 has the cam running directly in the head
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The problem with the CB750 was in the original design spec. The designers were told in the mid 60s that the CB had to be in the USA showrooms at the same price or less than the Triumph Bonneville. As a corporate decision it was a master stroke that almost single handedly broke the British bike industry. But from an engineering point of view it left the CB hopelessly compromised ie. cheap to manufacture. Hence the plain main/big end bearings, no shells for the cam, small ends straight in the conrods, plain primary chains, a frame that wont allow cam cover removal etc, etc. The Kawasaki 900 engine was designed to be the the best it could be (with 70s technology) and was far more expensive new than the CB. This cheap and simple engineering is what we are now fighting against 40 years on.
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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
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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.
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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
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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.
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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
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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
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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.
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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"
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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
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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! ;D
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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. :o
I'm now wondering if squirting WD40 in the drain holes will help displace the water.
Mick
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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
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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.
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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.
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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.
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Roy, you are a gentleman.
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+1 Roy is a gentleman!
Yes you are right about build down to price. My mates at school used to call my bikes 'Jap crap' because of linish marks in the chrome, unseen areas not polished or blasted finish and plastic chainguards etc. And in many cases the chroming finish was crap, hence the massive dealer warranty replacement programme they had for exhausts. But the one thing they did do right was double skinning the header pipes. Every 60's 70's Triumph I have seen has bluing on the header pipes. Plus they did not skimp on electrics. I reckon the build quality on the 70's Honda's was 1st rate. I suppose it's what we call value engineering these days. The other thing they seemed to get right was the metallurgy on engine parts as Mr. Honda was a qualified metallurgist.
Here's one for you Neil .. my collector box on the 400/4 I bought new from a Honda dealer had silver paint on some of the joints. Are the NOS ones you sold like that? Also the silencer has the HONDA stamping and HM377 on it but also SANKEI who I presume made it. Don't remember SANKEI on any of the originals I owned.
Cheers .. AshD
Whey hey another 13 posts and I reach the magic 1k!
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I've seen NOS with and without the silver paint. Ditto the Sankei logo. So at some point they started or stopped painting, and ditto the Sankei stamp, but I don't know when it was.
The as-new collector box I sold recently didn't have the silver paint, but I don't know when it was made.
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If you own a "leaky" bike and the oil is changed for example at 6000 intervals lets say, you may not even be changing the oil that went in at the last change.....if you you get my drift. ;)
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Got this below back from Rick Parkington of Classic Bike Magazine regarding the cam bearing shells fitted to the CB400F project bike they are building. Interesting stuff !!
Cheers ... AshD
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Hi Ash, Received your message to David Silver via a rather circuitous route! Afraid I can't offer much more information at present largely because the engine is sitting inverted on its head while I assemble the bottom end! I will by all means take a closer look when it's right way up again. Since the cam cover has no shells fitted, the cam diameter must still be standard and that means that if these are Kawasaki shells, it must be a model whose cam is the same diameter as a 400/4. My issue was that as a machining job it isn't one I'd like to undertake because the head design prevents starting from one end and boring straight through; it would be tricky to get right starting with an already worn head and it wouldn't have to be far out to seize. I'm guessing there's more slack on the fit than there was on the DOHC motors where the cam caps were not avaailable separately and disaster followed mixing them up... The cam cover is away for chrome stripping and polishing just now but I'm looking forward to plastigauging the fit of the cam when it returns. I can see it would be a big help to SOHC owners to find out how this was done (in my bike shop days I used to have a black museum of gruesome SOHC Honda cams!) but I have a feeling finding the shells may only be half the answer, it's a pity it looks like it was done before my mate bought the bike Cheers Rick
Hi Ash,
OK got bit more info now. The bearing shells in the head are not Z1. I popped one out and the number on the back is G (in a square) S8919M. The stamping looked similar to that on Triumph shells, so assuming it was a Glacier bearing I tried Googling the number but no result.Giving up on the Internet I did what I should have done first and checked my 1968 Glacier catalogue. Turns out they are from a Villiers industrial engine. The set number was B 1042 S and the engine is a Villiers Mk12 1.5hp, 120cc. The shells in the head are minus tens; turns out the Villiers standard shaft diameter is 0.874", I measured the cam at 0.864", so using -0.010" shells will make the fit right for the Honda cam. I suspect these bearings will be hard to obtain now but you never know.Speaking to someone yesterday who reckoned that back in the day Dixon Racing used to do cylinder head bushing operations, thy supplied the Yoshi parts so that would make sense.Thanks for the invite to the forum; not sure I'd have much to contribute, I'm afraid this is the first four I've laid a spanner on. Work aside I avoid the computer - too much to do in the shed. I actually started a blog this year (www.rickparkington.co.uk) and am having trouble finding the time even to do that! But feel free to use this info and pics. Hope it proves helpful.
All the best Rick P
[attachimg=1][attachimg=2][attachimg=3]
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What do you think Bryan. Do you remember Dixon Racing doing this kind of conversion?
This looks like a possible source BTW
http://vintagemotorcyclepistons.co.uk/page/5
Cheers ... Ash
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If you're really unlucky it's a Jock Kerr job - actually, he used roller bearings IIRC, and obviously on the ends of the cams only.
Joy Engineering used to do this sort of thing, I think.
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If you're really unlucky it's a Jock Kerr job - actually, he used roller bearings IIRC, and obviously on the ends of the cams only.
Joy Engineering used to do this sort of thing, I think.
Looks like it's fairly well done from the photos Rick sent so probably more like Joy than Jock Kerr !
Interesting though because sooner or later there will be a shortage of decent 400/4 heads 'cos everyone seems to be restoring them. Suppose the 350F head may fit though but not sure about it, as they are plentiful in the US.
Cheers ... AshD
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Some 15 years ago I was offered six brand new OE CB400F heads for a grand. Saw if I could flog them to DS first - he offered me something like £50 each. Turned them down, figuring it would take me years to get the investment back...
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I had a Phil Read Rep back in the late 80s and rebuilt it. Worked as a aircraft fitter and got the lads in the machine shop to line bore the carriers and they made dome phosphor bronze (I think) shells - cant remember the detail but shows its do-able. I done a few thousand mile without any problems before I sold it
Phil