Author Topic: What is a realistic lifespan for a CB500/550 camchain?  (Read 5485 times)

Offline deltarider

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What is a realistic lifespan for a CB500/550 camchain?
« on: June 04, 2020, 04:33:27 PM »
If I'm not mistaken, my camchain has reached the end of its lifetime. Again! This one has done 56.000kms (35.000 miles) and because it was already the 3rd, it has always received the prescribed care by me (even more!). Why are chain and/or tensioner so crappy? I wonder what experience you guys have. In other words: what is a realistic lifespan for such a camchain? Any tricks to prolong its lifespan. Do some brands like Tsubaki perform better than stock (DID)?
« Last Edit: June 04, 2020, 04:37:26 PM by deltarider »

Offline Trigger

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Re: What is a realistic lifespan for a CB500/550 camchain?
« Reply #1 on: June 04, 2020, 05:24:09 PM »
Life of a cam chain this small is 30.000 miles from Honda and DID advise  ;)

Offline nairb

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Re: What is a realistic lifespan for a CB500/550 camchain?
« Reply #2 on: June 04, 2020, 07:36:09 PM »
I have had my k3 from new.  With regular oil changes its done 42k miles....... You are making me think I should have replaced it when replacing the piston rings.
cb550k3, cl450k5, re5m, xs650xs2, mt500, kettle, gt550 x2,  gt380 Kz750 twin cb360K0

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Re: What is a realistic lifespan for a CB500/550 camchain?
« Reply #3 on: June 04, 2020, 08:38:02 PM »
Interesting topic deltarider, but not a simple answer I feel.

Which oil do you use and what change intervals?

Offline deltarider

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Re: What is a realistic lifespan for a CB500/550 camchain?
« Reply #4 on: June 06, 2020, 12:20:59 PM »
Thanks to you all!
... Which oil do you use and what change intervals?
Bike has been maintained well. Over the years I have used various oils. At the time it was Castrol GTX2 ofcourse. Last ten years it has been Castrol High Mileage and I must say I'm very pleased with it. It keeps everything clean and helps rubber seals live longer. I prefer 15W-40, because I won't operate the bike at lower temperatures than say 15oC. In long vacations I saw no problem doing 5000km before an oil change. Long rides and ideal circumstances. One day in Spain when I changed the oil - I had to renew some oil pump O-rings - the mechanic in who's workshop I did this, was surprised I didn't pour the collected oil back in again. I told him I had been riding 4-5000 km and it was time for an oil change. He kneeled, dipped his finger in it, rubbed it between thumb and finger, smelled it and concluded: "como nuevo" and asked me if he could have it for his Laverda. Below a pic of what the oil screen looked like after some 50.000 kms. Mind you, before cleaning! Also the oil pan was super clean. Never seen any sludge. Decades ago I found a chafe (is that the word?) of aluminium in the oilfilter housing or oil pan (forgot which). Could well have been from the drive chain eating in the crankcase. This was some 30 years ago.
Alas! In the meanwhile there's a new development. Let me look for the link.

Offline deltarider

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Re: What is a realistic lifespan for a CB500/550 camchain?
« Reply #6 on: June 07, 2020, 09:56:10 AM »
Here it is: http://forums.sohc4.net/index.php/topic,182917.msg2117148.html#msg2117148

I've been reading that one too. The reason for positioning is to make only tension on the front "pull" run of the cam chain,  leaving any excess placed on the run with the tensioner blade.
It's easier to see on the 750 motor with cam cover removed as all the rockers remain in place so you can observe the rotation sequence ( but it's the same for all these 4 cylinder motors) when you reach tdc one of the cylinders will have both cam lobes lifting the two valves for that cylinder,  with the risk that either one will turn the cam from it's own spring pressure.  This could bias the cam rotation in either direction (leaving the wrong run in tension) whenever you stop turning the crankshaft.  By specifying the 15 degree displacement it makes certain that the cam is trying to rotate backwards from the rocker spring pressure for that cylinder,  this holds the front / non adjustable chain run in tension for accurate timing,  and places any chain error next to the moving blade,  which you then reposition under it's own spring pressure and lock with the bolt etc to prevent any further movement.

If all the adjustment components are in good order,  and with the engine running smoothly ( possibly elevate the tickover speed to 1200rpm) then releasing the lock bolt will do the same thing as the motor will be pulling steady and consistent tension on the front chain pull down to the crankshaft.  It will achieve the same results, but if idle speed was fluctuating then there's a risk that front chain run will be pulsing with the routine not completed satisfactorily.

Offline deltarider

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Re: What is a realistic lifespan for a CB500/550 camchain?
« Reply #7 on: June 07, 2020, 04:41:15 PM »
Thanks a lot for explaining. Certainly helps us understanding. If anybody would have a broken or worn tensioner at hand, it would be great to have a video posted that demonstrates why it is so vulnerable. I can't help feeling the tensioner is not a supreme industrial design. Let's face it: Honda was not very good at camchain tensioners. CB350F/400F owners can testify this. Many run in a stuck tensioner sooner or later. The CB500/550 tensioner almost invites to abuse. Back in the day Honda mechanics had extra instructions from the technical department of the importer. We're a small country so dealers and mecs were invited to attend a one day training (not only on this subject ofcourse). Owners that did not receive the message (I did BTW), had to deal with information that was not very consistent to put it mildly. With the launch of the CB650 Honda did a smart thing: they put a cap nut over the tensioner bolt  ;D.
Not before Wednesday I will have time to have another look at mine. I have two options:
1. Just start the engine, listen and, if needed, try the dynamical method as described in the CB500/550K3 Owner's Manual.
2. Not start, but first verify if the bolt is still engaged or when it is not, can be persuaded to engage again. I suppose the limited movement (some thirty degrees) would tell me. This would mean I have to rotate the bolt very, very prudently.
I don't know yet what is be best, 1 or 2?
The reason I ran into this and have experimented a bit, is because I had become frustrated to perform the camchain adjustment procedure say every 300km. From all the replies here, I think it is safe to conclude that it is foolish to expect a life span of the camchain of over 45.000km, no matter how much you cared.
« Last Edit: June 07, 2020, 04:56:54 PM by deltarider »

Offline Bryanj

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Re: What is a realistic lifespan for a CB500/550 camchain?
« Reply #8 on: June 07, 2020, 05:28:01 PM »
Loosen the locknut and see if you can move the bolt BY HAND ONLY. If you can by more than a very small amount the tensioner is likely fubar

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Re: What is a realistic lifespan for a CB500/550 camchain?
« Reply #9 on: June 08, 2020, 12:42:08 PM »
The design of this system is worth discussion I feel.  Honda obviously made  choices during design and testing of the original,  principal among them is that the chain fits into a very small space for what it has to do.  Honda acknowledge that a gear drive solution is the ultimate in design but they are expensive,  take up more space and usually much more complex to machine and subsequently setup within acceptable tolerances.  The market position originally for this bike just wouldn't warrant that level of expense.

Saying that,  they did do a good job of designing the chain system within this era of engines.  There's limitations to all decisions and lifing is just one of them.  Acknowledging the practical life in service and crucially not have the chain break within that period could be viewed as more or less 100% successful,  after all these were effectively making 100 bhp per litre capacity from their design originally started in the 1960s . In  car terms of the same era that would have been an absolutely full race spec motor, fairly exotic and remarkable for a showroom production engine of any type.  They really are a pinnacle of engineering.

One of the limitations of chain drive,  particularly over such a wide rpm range are vibrations / harmonic resonance.  They will effectively twang like a guitar string if sufficient design and proofing hasn't been applied,  which if uncontrolled will dramatically shorten chain life. Generally all cam chains have their "pulling " run guided over an arc to prevent resonances building in that run as left in free air that's what they will do. 
Pedantic I know,  but any chain drive can't be tensioned.  The best that can be accomplished is to make provision to stop any slack from flapping,  hence the adjustable guide systems used. True tension would just add to the chain wear.
Where do the harmonics come from?  One set is the pulsing of cam lobes against spring pressure from valves which can't be removed but the long rocker faces mitigate this by running up and down cam ramps more smoothly.  The frequency of this will obviously change during rpm range.
The other obvious scource is the crankshaft pulsing at twice the rotational speed of the cam but much larger in potential size.  This is mitigated via engine design balance but can't be completely removed, but also affected by combustion balance and more specifically the carbs.  This is really what carb synchronisation is all about,  bringing best parity of each cylinder under load.  Smooth tickover is just a byproduct of this and not the primary reason for doing it.
Running the engine at true "under load " combustion parity will result in all the components being subjected to the minimum frequency loading.
The primary drive is also subject to these crankshaft frequency,  with it's own consequential lifing and performance.

Edit to add;- it's one of those odd transformations that the cam chain pulsing is most severe at lowered rpm than at the top of rev range if harmonics are well controlled.  In other words high rpm won't add to cam chain wear from it's own mechanical limitations, it's just that on a time basis the chain will complete more cycles for an equivalent mileage if you use lower gearing at elevated rpm. The wear is consistent if expressed in total engine revolutions completed as opposed to mileage the vehicle has travelled.

« Last Edit: June 08, 2020, 01:27:46 PM by K2-K6 »

Offline Bryanj

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Re: What is a realistic lifespan for a CB500/550 camchain?
« Reply #10 on: June 08, 2020, 02:55:30 PM »
On a side note, one of the reasons for CX500 cam chain wear was due to V angle the camshaft went from no valves open to most valves open in a short part of revolution

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Re: What is a realistic lifespan for a CB500/550 camchain?
« Reply #11 on: June 09, 2020, 12:20:10 PM »
On a side note, one of the reasons for CX500 cam chain wear was due to V angle the camshaft went from no valves open to most valves open in a short part of revolution

Yes Bryan,  that lompety-lomp drlivery would appear to set up a "unique" resonance within that motor.  They obviously learnt from it as both the F1 V10 3.0litre engine at (similar odd angle) 72 degree V of late eighties was very successful even though all the other manufacturers thought it couldn't work because of vibrations being difficult to resolve.
And then the MotoGP RC211V 5 cylinder 75 degree bike engine similarly dominated bike racing too.

Thanks Ken, yep I could of flown a sortie over here to disturb all the pigeons roosting,  there's crap everywhere from them  ;D

Offline deltarider

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Re: What is a realistic lifespan for a CB500/550 camchain?
« Reply #12 on: June 12, 2020, 03:47:59 PM »
Thanks again for your expertise. This is where I am. Engine starts rightaway and pulls wonderful as it should.
It seems my only option is:
a) Loosen the lock nut.
b) Prudently keep the tensioner bolt with a screwdriver counter clockwise (carefully avoiding to exercise force inwards ofcourse) whilst fastening the lock nut. I can also do this dynamically with a somewhat raised idle. If I release the screwdriver before fastening the lock nut, chain becomes much too noisy, so I conclude tensioner bolt still does something. How much? I have no clue.
Checked once more in the partslists if there have been any modifications. Nope. At CMSNL however I see the chain is superseded by 14401-362-003.
Looks like I have to live with a raised idle.

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Re: What is a realistic lifespan for a CB500/550 camchain?
« Reply #13 on: June 12, 2020, 06:40:30 PM »
To be clear,  you are saying that the camchain has now worn far enough that the guide's spring will no longer reach the distance to completely remove any slack?

Offline deltarider

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Re: What is a realistic lifespan for a CB500/550 camchain?
« Reply #14 on: June 12, 2020, 07:16:37 PM »
Frankly I don't know. What I do know, is that for the last few thousands of kms, I've done the adjustment procedure (either by the book or 'Bryan's method') mul-ti-ple times and that it helped only for a few hundreds of km. Man, I hate that crappy thing and I'm not the only one. It has been a nuisance from the day in 1980 I acquired the bike. First one went say around odo 46k km, second around odo 80k km and now I'm looking at a third F.R.T. of *7.6.

 

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