The Bullet: Mysteries & Myths -
Don't just love but get to know your bullet more

- by B. R. Gurunandan


Drive Chain Adjustment
Adjusting Chain-Tension, Chain-lash, Chain-play.....anything you say.


Chains. Those heavy, rusty, clanking contraptions that shackle you to the wall or ball, restricting your freedom, making life a misery.....Oooops.
Wrong chains !!

Here we want to discuss the adjustment of motorcycle drive chains. Chains that transmit the drive from the engine to the wheel. Those greasy, crusty, clanking contraptions whose quirks drive you up the wall, threatening your freedom, making life a misery.....Errrrrr.
Shucks !!

But chains do have a negative connotation for most of us. A pity, because these simple little marvels have held their own for ages against all other forms of drive-transmission such as shafts and belts that have promised a lot but have been so plagued by practical problems as to leave chains the preferred system in everyday motorcycles the world over.

Much of the messiness of chains is unfortunately unavoidable, as is their frequent maintenance. But the mistrust and apprehension we have is rather misplaced ! Here we shall try to understand some of the basics and see how to get the best out of this much maligned mechanism.

The basic issues are:
• How do they work ?
• Why do they "stretch" ?
• How should they be cleaned ?
• How should they be lubricated ?
• How should they be adjusted ?
• What're their problems & solutions ?
• When should they be replaced ?

How chains work is a topic for a textbook; here we are just going to ponder a bit on a diagram to grasp the construction, without bothering about the design aspects now.

We see that the chain consists of a set of side-plates, pins (rivets), sleeves and rollers. And that a diagram and actual inspection of the chain will yield much more information than a lot of text here. The adjoining diagram shows the construction and major friction/ wear areas. We can easily see that wear on the pins & the inside of the sleeves will result in chain-slack. Wear in the roller and outer side of the sleeve will allow the link to settle lower down on the sprocket-tooth. HL is Half-Link.

To quickly dispel a widely prevalent myth, let's note here that chains DO NOT stretch. In the sense, it is NEVER from the plates becoming deformed by stretching that the chain becomes longer. It is ALWAYS because of wear of the pins and the sleeves that the gaps between them become larger and allow the chain to become "longer".

The end result is indeed that the effective "pitch" becomes larger with use. However, it is not due to stretch but due to wear. This should be understood clearly if we are to service & maintain the chains properly and not waste good money on dubious "high-tensile" chains.

This is not to say that material of the chain is...errr...immaterial, because tensile strength IS related to hardness which IS related to wear, but it has been observed from experience that in motorcycle final-drive application, by far the more important factor is maintenance. Keeping the chain free of entrapped sand or grit, and keeping it properly lubricated increases the life of a chain very significantly.

Another very significant source of wear is misalignment of sprockets. Also very important is the quality of the chain as far as the dimensions go. Rare, but not unheard-of are those chains with manufacturing defects like seized rollers or pins reluctant to turn. Sure, they will run-in too, eventually, but the damage to sprockets and bearings is something hard to predict and totally unacceptable. There is only one use for such chains, but that is not in the scope of this serial. Ask the colleagues of Dawood if you are really curious.

OK, so if the chains deteriorate by wear, it follows that keeping them clean and well lubricated will increase their life. If you are still doubtful about this, I draw your attention to the fact that your primary chain and sprockets running in a clean bath of oil will outlast your final drive chain and sprockets by a factor of four to six.

Now that we have also seen the construction of the chain, and the place where the detrimental wear takes place, it is obvious that wiping a chain and squirting some oil at it while on the bike is nothing but an eyewash.

Sorry, guys, but the truth is that you HAVE to take off, clean and lubricate the chain periodically.

The grit we are trying to remove is trapped between the pins, sleeves and rollers. A solvent-moistened rag is NOT the answer. Swilling in solvent is.
Solvent being very difficult to dispose off as well as pretty expensive, I use a detergent solution to get rid of all the visible muck. After two or three changes of detergent solution, I go for a solvent-soak & wash. Outrageous, but it works :-)

Then you can either soak the chain in oil or "boil" it in grease.
The former method is very easy to implement, but the latter results in a lesser tendency to attract grit, thereby increasing the service-intervals. Also the lubricant remains in the intended place longer and that has very significant benefits.

Note that I do not even recommend any specific oil or grease ! I have done year-long comparative studies between different chains and lubes, and found that the really significant factor is ONLY the frequency and thoroughness of cleaning.

Because the Bullet has a primitive and difficult to adjust mechanism for adjusting chain slack, I start with two or more new chains. When one is dirty or slack I (clean the sprockets and) substitute it with a new one till that is equally slack. Meanwhile, that gives plenty of time to clean and lubricate the used one.

For lubricating, coil the dry chain and lay it on it's side in an old pan. Put it on a hot-plate. When it is good and hot, add grease in small quantities so that the level of the molten grease increases slowly to cover the chain.
Do not dump in all the grease at once, nor dump the chain in molten grease !
If you do, there is a good chance you have entrapped air under the rollers and sleeves, and all the effort is probably wasted !

Chain Adjustment
BTW, "Chain-adjustment", "Chain-Lash" or "Chain-tension-adjustment" are not technically correct terms, because what we actually adjust is the "chain-slack". But due to wide-spread use, we may as well accept them.

What happens if the chain is too slack ?
When ever the torque changes or reverses (you start accelerating or decelerating) the slack lets the driving sprocket reach a high angular velocity before it goes taut with a shock-load ! Much like a modern hangman outfit breaks the neck of the sentenced person, the shock loads on a chain make "steps" in the pins, increasing the pitch locally, leading to more shocks and wear.

Why not aim for zero slack ?
That is exactly what we should do !

Hey ! Kidding or What !
Not at all. But I'd like to qualify that a bit:
As close to Zero-Slack as possible, but NEVER in tension.

The Fatwa
Adjust the chain for 12/ 25mm slack in the centre.
....With rider, /with rider+pillion, /on centre-stand.
Effect of Sprocket-runout
....depending on the edition of the manual !!!



The theory
The slack IS required. For two reasons:
• One is to compensate for sprocket run-out where it exists.
• And because the drive-sprocket axis is NOT the swing-arm axis !
Neither seems to be understood by any of the REM authors !







Effect of Swingarm movementIf you adjust for zero slack
• at the point of maximum sprocket run-out
• with drive sprocket axis, swing-arm axis and wheel axle
on one straight line then you have got it right.



The method
First, some more theory !

The adjustment has to consider the following -
• the runout of both, the drive & rear-wheel sprockets
• the maximum chain-length required
• with the wheels in perfect alignment.

The maximum run-out can be found by feeling the chain-slack
over several rotations of the wheel.
Why several rotations ?
See the diagram showing sprocket-runout.
Remember that either/both sprockets can have runout.
With just one rotation of the wheel,
you may not get both sprockets in correct position.
This could be anything from immeasurable to several mm.

Zero Slack Adjustment PositionAt the position of least slack, measure it and take the
bike off the stand (careful not to change the position !)
and (here, you need the help of a heavy friend or two)
press down on the seat till the swing-arm is in line with
the drive-sprocket (check with a string against a mark
earlier made on the clutch-case)
At this position measure the slack again.
The difference is excess slack !
Leaving two to five mm (the less the better; depends
on the confidence you have in your work) for safety,
you can take up the rest with the adjusters.

But mind the wheel alignment !

Note that moving the same number of notches on both cams
does not always give proper wheel alignment.

You should check the wheel-alignment with a string.
(chapter soon to be added!)

Alignment of the wheels is a somewhat long-drawn process
because of the "notched cam" type of adjuster than the
screw-type ones found in most bikes.

But why...
Why go thru all this trouble instead of just giving it 25 mm slack ?

If your sprockets are perfect, then this slack is way too much.
Enough to make a very perceptible difference in the gear-shift !
(The primary-chain adjustment should be also optimum)
(chapter soon to be added!)

And the more the excess slack is, more is the general wear.
You'll have to find out for yourself whether it is worth it.

Isn't there a simpler way ?
Hahahahaha ! Bullet-eers do not need spoon-feeding !
Most of you would have already thought of this, but
for the sake of the others, a hint :
After adjustment as described above, measure the slack
with a tile under the stand so that the wheel is raised free.

The next time, (if no changes in suspension)
you can just adjust it on stand to this slack !!!
(Don't forget the run-out & alignment, though)

Now we still haven't covered the topic of chain & sprocket
service limits. To do it justice, it has to be dealt with in
a separate chapter for itself.
No, just kidding !
Actually, I've run out of pencils & patience for now.
Happy New Year !


By B. R. Gurunandan

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