Chain or sprocket problem ?

[The Gecko_imp]

Observations as follows:
- chain is 6000 miles from new, no problems, no wear or visible damage
- sprockets same miles, looking perfectly fine
- sprocket mounting looks perfectly aligned, all nuts tight
- chain slack adjusted as required, hasn't changed in over 1500 miles

Now please help me explaining this.
When I measure the chain slack at different positions by rolling the bike forward (she has no center stand) the chain slack is the same in all but 2 or 3 positions. In those positions (each plus or minus 2 inches) the chain slack is reduced to under half an inch. No other observations. Adding plenty of oil and let it sit hasn't solved the problem.

I cannot figure any scenario {other than visible damage to the rear sprocket) which could cause such strange measurements. And I have a hard time ditching a good chain without a plausible explanation.

Has anybody seen similar ?

 

[Aussieflyer]

Hello Gecko,
Excuse me if telling you stuff you already know ...
I think you have checked the chain and sprockets for any deformation or build-up of grit on individual links or teeth. Variation in chain slack is often as a result of the sprockets and their attachment points being ever so slightly out of perfect round, imagine an oval shaped sprocket. This is just something that we live with but do ensure that you set the min slack at the tightest point on the chain.

 

[The Gecko_imp]

Both your answers make perfect sense to me. Thanks!
You know, there is things you sort of know, but when you face the problem unexpectedly, your brain doesn't make the connection. Will measure carefully again, adjust on a track stand, all the rest ...

Now let me ask one more question: if if came to replacing the chain, (and the rear sprocket asit ain't a lot of work to replace anyway), would you replace the front sprocket as well. I have the feeling I wouldn't be leaning that way for the effort involved ... and just see. And you ? what would you do.

 

[The Gecko_imp]

While you typed your response (thanks - I agree !), I went to the neighbor and borrowed his track stand for the rear wheel.
And guess what, as soon as she is lifted up the problem is entirely gone. The problem only shows when the bike is rolled forward as described before.
And as the track stand lifts the wheel near the axle (unlike a center stand) the rear shock does not decompress when the stand is added. In other words ... the geometry (sag) doesn't changes.
How the heck can this be ?

 

[The Gecko_imp]

Won't sweat it, I promise.
It's just that I like to know my bike and all it's features and conditions. Bothers me when something so (seemingly) simple has an attitude.

 

[Gone in 60]

I've had a similar situation with my Bonneville. Checking the chain slack with the bike on the sidestand, as it's supposed to be checked, I found it consistently loose except for one area, where it was much tighter. But on the center stand, it was consistant throughout its length. I didn't worry about it too much, knowing that the chain was nearing the end of its lifespan anyway.

 

[the Ferret]

I got 37,000 miles out of my original chain and sprockets and have 38,000 miles right now on its replacement set

 

[The Gecko_imp]

@Gone and ferret: see - not living up to my promise - here is what bothers me after all.
If there was a little difference of say under 1/2" between measurements, whatever, I'd just leave it alone. But when I adjust the chain to about 35mm slack as by the book, and go back on the side stand I find the same 35mm. Then I role her forward to the tricky spot and I measure ~5mm. It feels super tight. And that means the gear box / forward sprocket will sense the same.
If I ruin the chain, to hell, I replace it. But if the tight chain - which I cannot loosen any further" - pulls hard on the gear drive for every revolution of the chain, that can't be good.
And I still don't know how come.

 

[the Ferret]

You always adjust a chain to spec at the tightest measured spot along the lower chain run.

So if it were me, I'd go to that 5 mm spot and adjust the chain to read 35 mm slack, and then measure it at the loose spots. I would not ride it how you have it adjusted.

I can't imagine a chain having a spot THAT much different than the rest of the chain in 6000 miles, but if it truly has that tight of a spot, I suspect the chain is toast.

I personally at 6000 miles would just replace the chain and continue to run the original sprockets unless they show extreme wear as in hooked teeth with pointed tops.

 

[Gone in 60]

I agree with Ferret on this one.

 

[The Gecko_imp]

Thanks guys, really appreciate.

 

[Inhouse Bob]

Chains and sprockets...
I was just cleaning things up (once a year whether it needs it or not) and looking at my chain and sprockets. Everything looks fine to my untrained eye but that means nothing. I have right around 32k miles on her. The teeth on the sprockets aren't hooked or overly sharp. The chain adjustment seems to have more room to grow.
So, how do I know when it's time for some new parts and when that time comes, where do I find parts? I have been googling parts and as far as I can find no one has OEM sprockets in stock. Lots of after market stuff to choose from but I would rather have the real thing.
Thanks in advance!

 

[peterbaron]

Most likely the OEM parts are best for our CBs, exept the tires

At 41K miles/no commuting, I already replaced front+back sprockets with chain/RK and rubber cusions as a set. Why, because they are constantly working together.
Chain and sprockets received midium- service and somtimes were ran 3K miles without any service during my Maritimes trips and including 300+ miles while raining per trip = no lube.
Minimum I needed to replace was the chain = 4 kinks/tight spots and vibration in 4th gear, the sprockets and rubber cusions would last much longer.

Now, at 74K miles I only replaced the chain/RK. I inspected the sprockets and these still look good. Also, I sevice my drivechain ass-y more often, every +- 500 miles with 80W90 synthec gear oil and wax combination RIGHT after my ride when the chain is still warm. This ensures proper and deep chain penetration!
I lube my chain after every wet ride, even my if ride was short!

For reckless riders, lacking services, harsh conditions, short distances/commuting, parts replacement is needed more often.

Remember, proper and adequate service gives your bike and its parts greater longivity.

For camparison, I drive my car/ATM 3x/week to work for 32 miles each way and 3/4 distance is hwy driving. I need all around pads and rotors every 85-95K miles due to wear and vibration when braking.
My wife drives hers to work 7 miles each way, no hwy. She needs her all around brakes to be replaced ever 50-60 K miles mostly due to corossion and vibration, some pads still left.
Both cars are garaged.
How and where one rides, road conditions and proper service intervals make a big difference.

So if you don't know when is time for some new parts just submit pics and our forum's experts will advise you acordiangly to make your decision.
Good luck.
:beerchug:

 

[peterbaron]

"Most likely the OEM..."

No problem with options and final decision.

 

[Lord Popgun]

The chain slack according to the service manual is 1-1.4” Yours is slightly out of spec and is on the loose end. Is it possible the chain is “clanging” on the chain guard?