Sunday, September 13, 2015

KLR Gear Change

In answer to the question about changing the gearing on the KLR, here is how it can be easily accomplished. A side note for the non-motorcycling readers: we change the gearing in order to maximize the bike's performance on different terrain. For example, if riding level land, you want speed. Therefore you want a low ratio number. With a 43 tooth rear sprocket and the 16 tooth front sprocket (also known as the counter sprocket) gives you a ratio is 2.69.  This is calculated by dividing the higher number by the lower:  43 divided by 16 equals 2.69.

On the other hand, if you are climbing steep mountain roads where you need lots of torque and not speed, you want a higher ratio. A 49 tooth rear sprocket coupled with a 15 tooth counter sprocket gives a ratio of 3.27.  With the higher ratio,  you give up speed in order to gain more torque. Think of a tractor, it has a lot of torque or power, but lacks speed. A red Ferrari has a lot of speed but no torque. So don't try pulling a 34 foot camping trailer with a Ferrari.

On a multi-country ride one encounters a wide variety of terrain, needing different gearing. Changing the gearing on the KLR can be easy or can be time consuming. Here is the solution I found to quickly re-gear the KLR to meet the demands of the terrain.

First remove the rear wheel from the bike.  The rear sprocket is not bolted directly to the rear wheel but to a coupling that sets inside the rear hub. Just pull the sprocket up and out to remove. Between the coupling and the actual rear hub is rubber cushioning.



Here is the rubber cushioning inside the hub. The cushioning is to absorb the push/pull jolts the drive chain places on the rear wheel giving you a smoother ride.

Here is a 49 tooth rear sprocket still mounted to the coupling. The six thick lugs sit inside the rear hub engaging the cushioning thus turning the rear wheel.


There are eight nuts holding the sprocket to the coupling. Not only is that a lot of work to remove to mount a new sprocket, but one should also use a torque wrench when tightening the nuts for the new sprocket.  Instead I carry a spare coupling with a different sprocket already properly mounted.  Then it is a simple process to change gearing by simply pulling out one coupling/sprocket and inserting the other.  Then install the wheel back on the bike.

If the rear tire wears out or has a flat, remove it and install the spare tire. To keep the same gear ratio, pull the coupling/sprocket from the flat tire and insert in the spare tire.  


To answer a question about the frisbee on the spare tire:  the spare tire is mounted on the tool box with the brake rotor facing up. If the rotor was facing down, the constant bouncing and banging around would bend or deform the rotor, making it useless for braking later.  A spare coupling with mounted sprocket is carried inside the toolbox, not here on the spare mount. The white ring under the wheel is a small frisbee to keep the aluminum wheel from being damaged by the steel mount.


With the rotor facing up, in order to protect it from weather and damage, a larger white frisbee is placed on top. Both frisbees are inexpensive Walmart items.


The large washer, a castle nut and clip hold everything in place. To make sure the spare does not disappear at night, a steel cable is thread through the spokes of the wheel, a gas can and locked to the toolbox. 

Little by little Da'mit is coming together for the big ride. This weekend the anemic factory horn was replaced with a Bad Boy air horn that will wake up any texting or dozing taxi driver...  instantly.


Getting ready for a side trip soon, will post photos asap.


Ride safe
CCjon









11 comments:

  1. Pretty cool setup! Do you need to add or remove links from the chain when changing the rear sprocket?

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    1. That has yet to be tested. Will carry a backup chain if needed. Almost too much space in the cargo box, nature hates a void you know.

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  2. Nice and simple solution to easily change the rear sprocket! Will you be carrying extra sprockets or projecting usage and not bothering?

    I wonder, if I'd done the above, would I have gotten a more torquey first gear on my V-Strom. Oh well.

    What is the weight of the rig without baggage but with full tank?

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    1. Plan to start with the road worthy 45 tooth rear, carrying a 49 tooth mounted on a spare coupling for the really tough stuff. OEM sprocket is a 43, too low a ratio for sidecar use.

      I did upgrade to a 525 chain which is heavier duty than the OEM 520 chain.

      Haven't had a chance to weigh it yet.

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    2. my v-strom rig had a 530 chain after the first model's chain stretched and came off the rear sprocket striking the engine casing and totaling that tug....fun stuff.

      the 530 chain was rated for dune buggies with a 16000 lb tensile strength rating.

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    3. That's sounds like more what a hack could use, though have not seen any 530 sprockets for a KLR. I understand you can run a lower number sprocket with a higher number chain but not the other way. In fact some of the mud/sand riders go that way, the extra gap between the chain and sprocket throws the crud out.

      So you were running a 530 chain on 520 sprockets?

      A KLR guru told me is better to go large on the rear rather than smaller on the front/countersprocket, as the smaller sprocket tends to wear out a chain faster. Have you heard anything like that? Smaller counter sprocket makes the chain bend around a smaller circumference, which on a well lubricated chain should not be an issue, but in real world conditions, I can see where that could be a wear point.

      Decided a rear sprocket premounted was an easier swap than trying to change a countersprocket any day.

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  3. Yep, 530 chain and sprocket.

    I'd not heard about a smaller sprocket tending to wear a chain out faster.

    I kind of like the idea of a smaller chain on bigger sprocket but wonder how secure it all is.

    What is your recommended chain tension adjustment measurement? I always had issues with the 1" recommended by the manual, folks told me it seemed the chain was too loose. Just one of the reasons I went back to tugs with final drives vice chain drive.

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    1. whoops, got that backwards.....I just can't wrap my mind around chains and sprockets I guess.

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    2. Re chain adjustment, I allow an inch to inch and a half movement on a slack chain, also abide by the theory of better too loose than too tight.

      If extremely loose, besides the risk of a chain coming off, then you get a jerkiness when riding.

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  4. A smaller front sprocket also puts more tension on the chain for a given ratio and has less contact area with the chain. This is in addition to the problem of more movement at every pin to wrap around the smaller front sprocket.

    So it is a well established "rule" to avoid smaller front sprockets unless you really need the clearance.

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    1. I like your reasoning, am amazed at the frequency of reading about riders going from a 15 tooth to a 13 tooth counter sprocket.

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