Drive Knocking

Hi all, I'm new to the forum and have been riding my 2002/3 cb500s for about a year and a half now, great bike and rock solid up to this point. 60k miles and good extensive service history.

Anyway for a while now I've been noticing a light knocking coming from what felt like the rear end when the clutch was pulled and I was rolling, I recently did a couple long distance trips from UK to Paris and when I returned from the last the knocking had got much more noticeable and is bloody irritating and not less than a bit concerning.

I've read the couple forums already posted talking about this being normal but that's nonsense, and the deterioration is testament to that. No bike should clunk like this let alone a Honda!

I've had the chain off and run the thing without and the drive sprocket is a bit loose indicating drive shaft wear, but the thing is clinking away like a tambourine, holding an edge against the sprocket the noise is lessened but a definite kick can be felt twice per sprocket revolution, any serious ideas to what this could be?

bearing failure, nut loose on the clutch side, gearbox breaking up?

Any help greatly appreciated.
Cheers
Chris

Cam chain tensioner? I've not had to deal with it myself yet but it seems to be a reasonably common failure point and there are plenty of posts on the subject

I'm wondering if the drive cushion rubbers are getting worn or perished on the back wheel, as this would cause a knocking noise from the rear end. Quick check would be to place the bike in gear on the centre stand and see how much rotational play there is with the chain immobilised.

chromedome wrote:I'm wondering if the drive cushion rubbers are getting worn or perished on the back wheel, as this would cause a knocking noise from the rear end. Quick check would be to place the bike in gear on the centre stand and see how much rotational play there is with the chain immobilised.

It's a good idea but he said it still does it with the chain removed.

Any knocking in the final drive has to be either at the front drive or rear sprockets. Ok, easy to check rear cush drives but.... movement at the front drive sprocket, as you describe, does not auger well at all and I'm thinkin shaft bearing problem. If it is, then it's not an easy fix, but it would need sorted in case something seizes.
It's not often they go and far as I know, one possible cause is the chain being run too tight for too long. You may have looked after your chain ok but you don't know how the bike was maintained before you got it.

I think Johhny10 is on the money here. I'd strongly suspect bearing failure, and you need to sort it before something more catastrophic occurs.

What you're going to have to do, before you touch a spanner, is a proper assessment of your spannering abilities, available cash, time, workshop space, overall condition of the rest of the bike, transport needs etc..

Anything is fixable, but whether it's going to make any kind of sense to do so depends on your circumstances. A full strip, check and rebuild with new parts, paid by the hour at a bike shop, is going to run beyond four figures I'd suspect. If you're having to pay someone to do the work then probably the cheapest and easiest option is to source a secondhand engine complete and get it swapped as one lump. If you're handy with the spanners, then source a secondhand engine that's already been stripped of it's heads and barrels (and thus much cheaper) and make one good engine/gearbox from the two; hopefully the rest of your engine (and indeed bike) warrants the work.

If you need the bike, funds are tight and you like it enough to want to keep it, then probably a complete secondhand engine from a lower mileage breaker makes the most economic sense whether you do the work yourself or pay someone else. Unfortunately, the price of spares and the time the work takes to physically do, makes a major repair on an elderly Japanese motorcycle a labour of love that really doesn't make a lot of sense in pure money terms. Another option is to either replace the bike complete and break your existing one for spares, or buy a complete bike to break and tidy yours up.

Not much help maybe, but hopefully I've given you food for thought. Glen.

Lot of the info in this thread is relevant if it is shaft bearing failure (should read "output shaft" in title though)


http://www.cb500club.net/t2558-crankshaft-oil-seal

Doesn't sound nice.

Just to clarify:

Is there side to side play/movement in the output shaft (not the sprocket)?

AFAIK there shouldn't be any movement - if there is it suggests that the bearing is on the way out, which, as mentioned above, can be a bit of a pain to fix (not by any means impossible, but not exactly quick and easy!)

Hey guys, thanks for the replies and thoughts, sorry for the delay in responding I've been busy with a new girl, 

As I mentioned I stripped off the chain and examined the cush drives, the chain is less than a year old and the sprockets where changed with it, the cush blocks allow no real feelable movement when the lot is assembled. 
The front sprocket does seem to have considerable play which would make me think the splines have had it, but the kicking though the final drive would indicate to me either the gearbox is shagged which would seem unlikely, or that the output shaft bearings are dead alowing the drive to not engage fully or something, but pulling about on the shaft reveals no discernable movement apart from the sprocket itself. 

I replaced the cam chain tensioner when I got the bike and the tapping of that which came with the bike was easily fixed with the new one and didn't provide any feel in the ride.

I was wondering if the timing being off could give this kicking sensation, but the bike would likely not run at all if it was off enough to affect this.

I have been perusing secondhand engines on ebay and looks like a low mileage replacement (say 22000 miles, less than a third of mine) is attainable for about £260 which would be maneagable, I could then strip down and investigate my original engine and see if its salvageable and sell it on maybe.

Thoughts again thanks for the advice chaps!

Just to confirm just wandered out and tried tugging and twirling the drive and it feels smooth and only rotates in the sense expected, the sprocket is literally rattle loose though, the nut is tight up and the washer just leaves a slight clearance, I noticed this when I changed the sprockets and remarked on it to other bike users at work but we assumed it was simply a honda feature, could it possibly be damage to the clutch basket also? I was planning on opening up the case to have a look at some point. Maybe not an original washer and just a completely wrong fit, I'm not sure is the sprockets on these engines are meant to be hard on the shaft? The honda engine on my 125 Gilera Coguar when I was learing had the same sprocket arrangement.

If the sprocket is loose on it's splined mount, that could be the problem. My bike was like that when I got it. Previous owner had fitted a sprocket which didn't quite fit. I replaced with with a DID chain and sprocket set and hey presto problem fixed.

Still don't think that would explain the thrust like knock but I'll change the washer over with one that holds the sprocket hard and see if it makes a difference.

christodius wrote:Still don't think that would explain the thrust like knock but I'll change the washer over with one that holds the sprocket hard and see if it makes a difference.

You really should try that - it's a lot easier/cheaper than replacing an engine.

On the subject of engine replacement - it isn't too bad; assuming you have some trust that the one you are buying is better than what you've got!

I don't know if you have the time/inclination, but one idea would be to try and find a cosmetically ratty bike with a good engine - at least then you can ride it before swapping it over.

christodius wrote:... the sprocket is literally rattle loose though, the nut is tight up and the washer just leaves a slight clearance, ...

Sounds like this is your problem.  There shouldn't be any axial play in the sprocket.  Definitely agree with the washer idea. 

If theres radial play then that could be a sign the splines are worn, maybe as consequence of the loose arrangement.  Would be worth having the sprocket off just to check the spline condition (on sprocket and shaft).

Could using a front sprocket without a cush drive damage the bike in any way? Honda must have put one on for a reason..

Hi again chaps, I've just had the sprocket off and had a good twiddle of the output shaft and seems secure and free spinning happily.

I haven't got my Verns with me to take some measurements but I don't see any visually noticeable wear, in this evening light anyway, since it was loose when I fitted it I'm going to assume either the splines are worn, but based on the hardness of the output shaft I'm going to further assume the sprocket is at fault and was perhaps just a poorly made fit to begin with, as it is not thick enough to cause the washer to engage with it over the length of the output shaft, 

shoddy fabrication, so I'm going to buy a replacement higher quality sprocket as the chain and both sprockets show no tooth wear whatsoever and see if its a better fit, may come up with a better washer solution also. Will keep you informed if it solves the issue.

It's certainly worth a try. As you can see from here:

http://www.lingshondaparts.com/honda_motorcycle_parts_selection_pfk.php?block_01=13MY5WEA&block_02=E__1600&block_03=1612

(assuming you are talking about part 25?) a new washer isn't that expensive, even from Honda...

I think you are probably right in thinking that the movement may have worn the inside (drive) teeth on the sprocket, which in turn, will have only made the sloppyness worse.

Fingers crossed!

  Sounds like a result!
Lesson in this thread is to check the simple things first, instead of fearing the worst.

Hi all, not sure if your still following but I've done the following:

So new sprocket I machined up a packer, and locktighted it on the drive spline as there was still rotational movement, so its glued on now and bolted up tight, new cush drive, chain removed, cleaned thoroughly and re oiled and replaced, all in all the noises and major knocks are completely gone and its better than its ever been.

My issue is I can still detect the engine knock which I identified when I had the chain off and I let the engine spin the drive sprocket in first and I held a socket to it, its feels a bit more like a kick than a smooth power input on the power stroke, is this normal for the 500 engine? so when I'm rolling along I pull the clutch fully and its beautifully smooth now but I can feel this knock in my foot, its pulling like a horse on fire, but maybe a bit rougher than it should be?

Thoughts

You can feel a *bit* of (normal, at least on my bike) engine vibration through the footpegs, which might be what you are feeling.

I wander if you should try and meet up with some other people with CB500s - you could then compare your vibration vs. theirs.

Sounds like a plan, short of any other major engine mechanical failures I've booked in to have the carbs balanced as I've never had this done in the time I've had the bike, I moved it around the building to wash it last week and noted one exhaust was already too hot to touch and the other only warm, so maybe a slight carb imbalance could be the cause of this knocking drive sensation?

It is worth balancing the carbs if you can - you can build a manometer out of some clear rubber tubing and water (or oil)!

While you are there, if you don't know when your spark plugs were last replaced, it might be worth doing that as well... just in case (not too expensive either).