What is a realistic lifespan for a CB500/550 camchain?

[Bryanj]

So buy a genuine did chain and a rivet link for a 500 twin, chain is same size

[Trigger]

I can't see what the big problem is. Pop the engine out and give it a full service, new OEM primary chain, new primary rubbers, new cam blades, check that the spring has not gone weak on the tensioner and you can always upgrade to a DID FTH chain 
Look after your bike and your bike will look after you 

[deltarider]

The thing is that I don't like to invest in a part that is crappy by design. I've clearly understood from you that the camchain has a limited lifespan, just like distribution chains/belts in cars. I trust the quality of the chain itself is OK, as it has been used in many other bikes, also onwards. The tensioner is a different thing however. All those 40 years I have serviced it as it should, either by the manual or by Bryanj's method. In the past, out of curiosity, I have once or twice, very prudently, turned the bolt clockwise and have it seen return by the spring just like it should. Personally I see no harm in this, although I will not recommend to others. If you are less confident, don't do it. The bolt is not to be pushed inwards as the manual warns explicitly. My actions in the past have not damaged the tensioner, but somebody less careful, could! Towards the end of the camchain's life, one cannot help suspecting there is something wrong with the tensioner. Is maybe that lock nut slipping and could an extra washer help? The mistake I made is, when I tried to get that nut of, I realised too late that the slot in the bolt had widened a fraction, just enough to prevent the nut to come of. By then, I had accidentely turned the nut - and now also the bolt! - a few rounds too much. I have not felt any resistance whatsoever!
In the past Honda has instructed dealers and mechanics a different approach. Unlike Bryan, I don't think it was ment to gain time. The Dutch mec I had the information from, told me he usually asked his collegue to exercise pressure on the kickstarter while he loosened and fastened the locknut. I don't see much time gained in asking a collegue to assist over the procedure where you yourself position the crank to 15^o ATDC. Honda choose not to publish the trick in later Owner's manuals but for a reason they only know, from the CB500/550K3 on, recommended to do it dynamically... And with the launch of the CB650 the method had changed again... By then Honda had wisely fitted a cap nut on the tensioner bolt...
Back to the tensioner bolt. I wonder if it would have helped, had Honda used an 8mm bolt. I have never had a tensioner in my hands, but from what I've seen - not much - I have the impression the gear is made of some sort of sardine tin. My question to you, the experts, is: isn't there really something that could have been made better? Honda obviously has reasoned the bolt was not to be turned by a screwdriver anyway until its final moment: the removal. Hm.., from the CB350F/400F we know that the gear does have to be helped occasionally. Sorry for the long post, but maybe there's something useful in it for others. Anyway, I hope to post a sound recording as soon as I have managed to understand my smartphone.

[K2-K6]

It's clearly the chain life that brings up these questions,  the consequent discussion of adjustment is singularly dependant on the pace of the chain wearing.

What Honda have done is effectively brought to a halt the process by giving the required amount of adjustment it had determined against it's engineering specification.

If the chain pitch increases to excess then the mismatch with dimensions of the sprocket teeth will facilitate a situation in which the chain will attempt to ride on the peak of the sprocket tooth,  it's extremely likely the chain would snap in that scenario.  Preventing further tensioning at a safe limit is very prudent design in my view.

The primary problem is how fast the chain wears in normal service.  Consensus appears to be not more than 40,000 miles (and realistically the same for primary drive) with any improvements or interest in extending it's life focused on this as opposed to adjustment specifically.

You could determine that the two chains effectively are located if not at the edge of the oil's protective ability or perhaps just outside that range for ultimately ensuring that the wear is mitigated by scheduled servicing.
As most of the other engine and gearbox components don't wear at the same rate,  they in turn show that the oil effectively has them covered.

This type of difference (if it was determined that it needed attention) during original durability testing,  could be affected by different oil spec as it's not going to change much from components.

It moves into the area that general opinion gets spooked by, namely friction modifiers.  There's an oil spec closely related to the one used  by you (deltarider) that should offer increased protection of these components to effectively increase their life.
I think it's worthwhile to consider that path for longer term usage.

[Bryanj]

I agree with Trigger, there is nothing inherently wrong with the500/550 tensioner(or the 750) the only possible problem is maybe a not so good technical translation in the books and a lack of mechanical understanding of operaters

[deltarider]

Unlike most of you, the primary drive chain is the one I'm least worried about. The design is such that it can handle way, way more load than the power a CB500 can ever put out. Naturally it has some play; after all, it has done 136.000 km. I just don't see it break. Under load my bike is as silky as new. And about that eating in the crankcase, well, we'll see.
History. At around 45000 km I had a Honda dealer do a topend, because I was fed up with what I thought was a leaking head gasket. Replacing the tensioner and camchain at the occasion was just a sensible thing to do. At around 80k km, I thought it was time to have another one done. Oil sweating again ofcourse. Replacing the tensioner and camchain was again part of the job ofcourse. Next week I will carry out some extra checks regarding the ignition just to be 100% sure. Bike is a still a joy to ride and easily accelerates into red zone in all gears except 5th. 

[Bryanj]

I stripped an abused US engine that had done less than 30,000 and the primary chain had worn through the casting to the oilway

[deltarider]

In Holland a ton is not uncommon for that chain. Always having the timing correct and the carbs well synced, helps, i guess. As said before, it is more than likely mine has eaten into the crankcase also. I have found a chafe of aluminium once in the oilpan or oilfilter housing (forgot which). When? At least some 50.000 km ago.

[Bryanj]

With sump pan off you can feel how deep a groove the primary chain has worn into the gallery.
Ken i think the 550 was recast in that area, the one i have seen only had light marks not heavy gouges

[Trigger]

Sorry Ken, I have seen these primary chain break. Have come across two in my life. I will put a picture on that a customer sent me with a link in the bottom of his sump pan, later when I stripped it, I found the chain link pins.

I have also come across some that bad that, they have worn the teeth on the crank and bent over the cog teeth on the primary drive 

The aftermarket chains are crap that Sliver sells as a OEM replacement and the Honda ones are £££

[Trigger]

[ Guests cannot view attachments ]

[K2-K6]

Agree with Trigger.

These primary chains (Morse,  hi-vo, silent etc ) have a huge ability to mask their wear even way past optimum.

The tooth form changes as they bend from straight run to curving round the shaft taking up dimensional slack (hence why they are often referred to as "silent type" ) so masking how worn the pins are.
Also one of the design "characteristics " is that they centrifuge at higher speeds,  again masking faults at higher rpm too.  It's possibly this part that has the highest ability to machine the cases.

Doesn't mean they are not worn though by conventional judgement, but they can hang on until a pin ultimately gives way and fail instantly,  you don't get any real warning.

[Bryanj]

Same as they didnt put a new chain in the cx500 tensioner mod kit so you ended up doing them again at about 30000

[Bryanj]

I know, i surprised the rep by doing one well inside warantee time, left the front pipes rad and rad cowl all on and put it nose down on a n old matress.
I take it you knew about putting the first pint of oil down a rocker box to fill the cam lobe "sump".

[deltarider]

Yecch, that's some nasty sludge in that oilpan.