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Variation in rear chain tension


Journeyman

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Journeyman

I'm just wondering how normal is the  variation in the rear chain tension  on the NC750X. I've had my NC since new and the chain tension difference of a half turn rotation of the rear sprocket is about 10mm. I can feel the whipping of the chain through the pegs when the bike is under load. 

 

I replaced the O.E. RK chain after 4000 miles because the links were very stiff and adjustment was difficult with tight spots. The replacement DiD VX2 chain did not improve the tension variation but it is somewhat smoother feeling. This chain has now done 4500 miles and is cleaned and oiled approx every 300 miles and never sees rain. The rear chain alignment marks are spot on and the wheel bearings are good.

My other bikes never had this much tension difference and would like to know if other NCs are the same.

 

 

 

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Usually I fine tune by 1/6 of a turn using the 6 'faces' of the nut as guide. Did also this on previous bike whcih was a transalp

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Grumpy old man

Not quite sure what you mean by half turn of the rear sprocket, do you mean half turn of the wheel or half turn of the adjuster screws?

Edited by Grumpy old man
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Journeyman

I meant half a turn of the wheel. When the bike is on the centre stand and I move the back wheel by hand the chain tension varies by 10mm in one half turn of the wheel. When the '43T' stamp on the rear sprocket is at top the chain is 10mm tighter than the 6 o'clock position as measured with a ruler placed next to the chain without touching the chain. I just think this variation seems a bit excessive. 

 

I always use the flat of the adjuster nut equally on both sides to adjust the chain.

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Tex

Two things to look at. Is the rear sprocket running truly concentric? It should be, but it’s not certainly unknown to have a faulty one. The second possibility is the chain itself having a tight spot, but that normally takes more than half a turn of the wheel/sprocket to show up.

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Grumpy old man

Well mine is quite consistent, Think I'd be looking at the sprockets but I'm sure some one will come back to you with more knowledge than me.

 

I'll be keeping my eye on this one, good luck.

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Grumpy old man
1 minute ago, Tex said:

Two things to look at. Is the rear sprocket running truly concentric? It should be, but it’s not certainly unknown to have a faulty one. The second possibility is the chain itself having a tight spot, but that normally takes more than half a turn of the wheel/sprocket to show up.

And it is his second chain.

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Tex
6 minutes ago, Grumpy old man said:

And it is his second chain.

 

Which tends to confirm he has a wonky rear sprocket. You will normally need to rotate the wheel more than once to find a tight spot in a chain. If it goes tight-loose-tight-loose with every revolution the sprocket is (technical term alert) ‘pissed’. 

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Grumpy old man
1 minute ago, Tex said:

 

Which tends to confirm he has a wonky rear sprocket. You will normally need to rotate the wheel more than once to find a tight spot in a chain. If it goes tight-loose-tight-loose with every revolution the sprocket is (technical term alert) ‘pissed’. 

A little like me now:D

  • Haha 2
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embee

Definitely worth checking the pissedness  run-out of the rear sprocket, a wire pointer held on the swingarm and bent close to the sprocket should enable you to judge by eye if there's anything clearly out. Sounds like it's directly a result of sprocket rotation.

As a next step it'd be worth checking the bearings in the wheel and sprocket carrier, need to take the wheel out to do this. Wheel bearing failure is not that uncommon for some reason, sprocket carrier bearings rarely cause any issues.

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Journeyman

Thanks for your replies, it's certainly got be baffled and I've done my own servicing for 50 years now. I did take the wheel out to check the wheel  bearings and they seem fine. The back sprocket  seems ok as well, running true like the front. A friend has had a look at it and confirms the symptoms and also looked at the run out of the rear sprocket.

 

I have set the tension at just over 20mm for the tightest spot which makes 40mm at the slackest spot when pressed with my fingers. I will leave it as is for the time being,  the DID VX2 is coping and I do keep it well maintained. I may try a new rear sprocket later, these are the original Honda sprockets. At least I know that this tension difference is not normal for this bike, thanks.  

 

Edited by Journeyman
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Journeyman

 

Update

 

I couldn't ignore it any longer so I ordered a JT rear sprocket which I received today.

 

Looking at the two sprockets the O.E. Honda sprocket shows minimal wear for its' 9000 miles and it looks ok  regarding symmetry but I am no engineer. I didn't spend much time comparing the two sprockets so I got on with the installing of the JT sprocket. After getting the tension set about 35mm and the alignment marks even and the axle nut tight I spun the wheel and success, just a small 3mm variation with no relation to the position of the back wheel. So the slight variation is just the normal chain wear tight spots, it has done nearly 5000 miles. I went on a short ride it does feel better now with less feedback from the chain :ahappy:

 

I've had the bike from new in 2015 and was aware then of a slight roughness from the rear chain. I put this down to a poor quality O.E chain which I replaced after 4000 miles with the DID VX2.

 

So there must be something wrong with the O.E. sprocket or the original installation of the sprocket as these are the only things that have changed. Whatever, I've enjoyed riding the NC and will enjoy it more so now. One thing I don't like is the mess from using gear oil on the chain, I will continue to clean it with Kerosene as I used to do but use the dry chain lube that seems well regarded, as I only ride in fair weather. Thanks for pointing out that it could be bad sprocket problem, I assume these  things to be spot on nowadays!

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Tex

Glad that all is well now. It’s obviously been like it from new and your poor old chain will be grateful you binned the sprocket.

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trisaki
On 19/05/2018 at 13:04, Journeyman said:

Thanks for your replies, it's certainly got be baffled and I've done my own servicing for 50 years now. I did take the wheel out to check the wheel  bearings and they seem fine. The back sprocket  seems ok as well, running true like the front. A friend has had a look at it and confirms the symptoms and also looked at the run out of the rear sprocket.

 

I have set the tension at just over 20mm for the tightest spot which makes 40mm at the slackest spot when pressed with my fingers. I will leave it as is for the time being,  the DID VX2 is coping and I do keep it well maintained. I may try a new rear sprocket later, these are the original Honda sprockets. At least I know that this tension difference is not normal for this bike, thanks.  

 

Chain slack should be checked at the tight spot and set approximately 35mm not your 20mm 

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Journeyman

I know all that triaski but I had to set that way to avoid the slackest section being over 55mm until I'd located the problem with the rear sprocket. I am not a novice concerning bike maintenance.

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