Chain Tension Issue

[Miztaziggy]

...will shorten your chain by 1.2mm at its worst, which can quite easily have the effect described.

Nope still doesn't add up to the stated effect of "3mm to 11mm"

Shortens chain by 1.2mm. That doesn't mean tight spot of 1.2mm up and down. In effect you wind out the adjuster 0.6mm, shortening top and bottom of chain by 0.6mm and 1.2mm combined, which has way more effect on how much chain moves up and down.

[Wicky]

Renthals quality control allows 0.3mm variance on this measurement. The measurement being from the bore, to the bottom of the tooth well.

As mine was 0.2mm it was within spec.

In the image is that what I've indicated in red (a)?

If that's out by 0.2mm but within tolerance where is the significant ovality of the circle of the sprocket? Is it something you can accurately measure i.e the diameter in vertical and horizontal axis and the difference.

[AMCQ46]

I am an engineer [but I have forgotten everything I was taught in uni!] and I have been looking at all the calculations and here is my take:

It sounds like the problem with the sprocket is concentricity of the tooth ring to the center bore [not ovality].........so the tooth ring diameter is not changing [so no diff in the circumference = Pi * Diam].

the only factor which is changing is the effective center of the sprocket, and that is changing by double the measurement variation (a) in Wickey diagram = 0.2*2=0.4mm.

So the variation is the equivelent in pulling the tensioners back by 0.4mm. I am at work so cant go to the bike, but I will bet the thread pitch is 1mm or less, so it is the same a turning the adjuster by just under half of a turn................is that enough to change the slack in the chain by 10mm?............I think it is close to that

As I am not near my bike I then did a desk experiment I looked at the basic trigonometry of the chain.

The effect of the move in the sprocket centers will be seen on the top and bottom run of the chain, so that will give you a variation in chain run length of 0.4*2=0.8mm.

I made a rough estimate that the distance between the front and rear sprocket is about 600cm [6000mm].
To calculate the slack I assume the top run is tight, and the lower run has the slack. so approximated this to 2 right angled triangles each 3000mm long [x axis] and the chain slack of 30mm [the y axis].....[yes it would be easier with pictures, but I dont have time to scan ny notes and post].

the 3000 is half the true distance between the sprockets, the 30 is the chain slack, then the hypotenuse will then be 1/4 of the actual chain length.

with a slack of 30mm, the hypotenuse [sp?] of this triangle is 3000.5mm.......so that [in my head] indicates that a change in chain centers of 1mm would remove all teh 30mm slack [0.5mm for each of the 3000mm triangles].

so 0.4mm change in chain centers would equal 12mm change in slack by that geometry rule.............so yorky is correct.!!

Wickey, if I am being honest with you, I started this reply believing I was going to prove you correct, but the sums show that 1/2 turn of the adjusters would make a big change in the chain slack [even if the change in length is small].

So the conclusion is.............. set your chain tension at the tight spot and dont stress about the rest of it!

[tony.mon]

I have forgotten everything I was taught in uni!

I made a rough estimate that the distance between the front and rear sprocket is about 600cm [6000mm].

That's a very long swingarm.............Building a drag bike?

[AMCQ46]

Lol......schoolboy error

So with headmaster Tony checking the homework, and a quick recalculation I now estimate that 3mm of movement on the axle will give 30mm slack. So a 1 to 10 ratio.

0.4mm change on the axle is equates to 4mm less slack in the chain.

But perhaps by tomorrow I will have a new calculation

[AMCQ46]

Amazing what your brain does when you are sleeping! I woke this morning with a further correction to the estimate.
My model for chain slack was only assuming the movement from the nominal line of an over tightened chain to the lower position, but the reality is that the slack includes the deflection above the nominal as well. So real slack is double my 30mm model. So the ratio for sprocket centre distance to chain slack is not 1 to 10, it is 1 to 20.
So 0.4mm move in the axle position will approximate to 8mm change in chain slack.

[tony.mon]

This feels about right, assuming a 1mm pitch on the adjuster a slack chain moves back into adjustment with half a turn, usually.
Although the slack is on both upper and lower sections of the chain, one section is held taut by acceleration or deceleration, and so all of the slack appears to be on one side only.
And deflection is positive and negative, so add the two together to get the full deflection

Experiment has supported the theory, theory proven, QED.


Now, does anyone have a detailed knowledge of harmonics?
I'm sure you could work out load/tension/slack/primary secondary and complex harmonics equations- a swingarm-mounted strobe and timed shutter speed high-speed camera might help.


Maths was never my strong point, but I sure as hell can make things complicated.....

[benny hedges]

Now, does anyone have a detailed knowledge of harmonics?
I'm sure you could work out load/tension/slack/primary secondary and complex harmonics equations-

i tried playing one once but couldnt get the hang of that button thing on the end.

[Mike TW9]

Think I've diagnosed my own chain tight spot issue- the soft link is longer than the rest, in fact you can see it is by the longer gaps between the adjoining outer links. The tight spot occurs twice for every complete chain revolution as the longer link travels around each sprocket. The chain is currently adjusted so that it is over-tight at the tight spots, but it can clank the exhaust with over 1 1/2 inches of free play in the middle otherwise (not when riding I think). Also, when riding alongside a wall that reflects sound well, I think I can hear a cyclical chain noise, with the frequency matching the chain rotation. Aside from this issue, the rear sprocket looks fine, I've done c. 5k miles on the chain since buying the bike when then chain looked pretty new. The adjusters suggest the chain is probably a good 50% worn. I've kept it well lubed and clean, but suspect I've had this issue for a while. I've a feeling dealing with the tight spot would give noticably smoother drive.

Any comments? Replace just the soft link or whole chain? Front and rear sprockets too?

[tony.mon]

I'd replace the link with the correct one, and see if it improved the tension. If not, just replace chain and sprockets as a set.

[Mike TW9]

I'd replace the link with the correct one, and see if it improved the tension. If not, just replace chain and sprockets as a set.

Cheers Tony!

But more questions...

Firstly, which one to buy? I've looked here http://www.motosport.com/motorcycle/dri ... r1000;1998 (scroll down most of the way for the soft links) and there's a good few to choose from. I know split links are ruled out, but 520, 525 and 530 sound like different sizes and there's rivet or ring too, so which one to choose? Do I need to know what chain I've got/how can you tell?

Also, what tools do I need? I can lay my hands on an angle grinder and amazingly, I just located my old link extractor that hasn't been used for 20 years or so. Looks like good advice here http://www.visordown.com/workshop/diy-c ... /2421.html. Assuming rivet link is the right option I'm thinking sealing the rivet is the tricky bit as I'm not a "blacksmith or engineering apprentice".

Thanks again!

[MacV2]

I'd replace the link with the correct one, and see if it improved the tension. If not, just replace chain and sprockets as a set.

Cheers Tony!

But more questions...

Firstly, which one to buy? I've looked here http://www.motosport.com/motorcycle/dri ... r1000;1998 (scroll down most of the way for the soft links) and there's a good few to choose from. I know split links are ruled out, but 520, 525 and 530 sound like different sizes and there's rivet or ring too, so which one to choose? Do I need to know what chain I've got/how can you tell?

Also, what tools do I need? I can lay my hands on an angle grinder and amazingly, I just located my old link extractor that hasn't been used for 20 years or so. Looks like good advice here http://www.visordown.com/workshop/diy-c ... /2421.html. Assuming rivet link is the right option I'm thinking sealing the rivet is the tricky bit as I'm not a "blacksmith or engineering apprentice".

Thanks again!

You need a 530 chain, 102 links with the sprockets. Std size for the sprockets is 16 tooth front, 41 tooth rear. You can play with different size sprockets to lower or raise the gearing but a/it will mess with your speedo readings unless you fit a speedo healer & if going up in size you may need a different lenght chain...Oh & deff go with steel sprockets, alloy ones wear quicker.

It's worth getting a new set of cush drive rubbers as well, unless you have replaced them recently yourself you don't know how old they are..Do not buy used ones, get new ones.

http://www.ebay.co.uk/sch/i.html?_odkw= ... s&_sacat=0

As for the chain you pays your money...best not to buy cheap but expect to pay £80 + just for a chain. There are plenty of kits on e-bay go for one of the big names, DiD are a good choice, then decide if you want a black or a gold one...O ring, X-ring choices choices...

As for fitting it...if you rivet it up off the bike you have to get bike up off the ground, wheel out, nearside front footrest hanger off then you can swap the chains over...

If you need help, bring it down to me...

[Mike TW9]

Cheers!

I was intending to try Tony's first suggestion first- replace just the soft link as I'm pretty sure that's the issue- you can see the existing soft link is longer than the rest just by looking at it & when it goes over the sprockets the chain pulls tighter. So I think I need this: http://www.wemoto.com/bikes/honda/vtr_1 ... ivet_link/.

As for fitting, if it can be done with the wheel on and without a specialist tool to seal the rivet, I hoping to sort it myself. If not, I'll take you up on your pm offer.

Fantastic forum for an awesome bike!


,

[tony.mon]

Should you need it I think I have a brand new steel sprocket somewhere in the stock shed.
And a barely-used front, but that may be 15 tooth.
As I ran a tuned engine, I didn't need to drop the sprocket size for better acceleration, which is why the front one was only on for a hundred miles or so.

[Mike TW9]

Thanks guys,

I checked the chain against the rear sprocket and there's no slack except with the soft link. You can see that the space between the outer soft link and the adjacent one is much bigger than that between the other links:


The rear sprocket isn't visibly worn:


And I think the tensioner is about half way (currently adjusted over-tight at the tight spot):


So I'm inclined to stick with just replacing the rivet link. It sounds like I'd struggle to seal the new rivet without a specialist tool, so I'll either take it to a shop or visit the Macster.