2011 650 sprocket change - Kawasaki KLR 650 Forum
2008+ KLR650 Wrenching & Mod Questions For repair, maintaining or modifying discussions related to the newly updated 2008 and beyond, Generation 2 KLR650 Motorcycle.

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post #1 of 35 Old 09-20-2013, 09:28 PM Thread Starter
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2011 650 sprocket change

I have a 2011 klr 650, it's my first KLR. I'ts about a 50/50 split on where I ride, between highway and off road, I'm wanting to do a sprocket change, I read that the stock front is a 15 tooth, and I'm thinking of dropping to a 13 for more grunt. I don;t know how many teeth the rear sprocket has, what is it? should I go down 1 or two teeth in front,? Or go up 1 or two on the rear? Or do both? Maybe a 14 on the front and up a couple on the rear? With the stock sprockets I've hit 100 MPH on the interstate just to see what it would do. I haven't counted the teeth on the sprockets I'm assuming there still stock, I bought it a my local dealership, it had 2,500 miles on it, Now that I think of it, I should count the teeth to make sure what I have. Let's for now assume there stock, I don't want to climb a tree, but I do want more low end grunt thru the sand and ash, and mud. what do you fellows think. LOL
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post #2 of 35 Old 09-20-2013, 10:48 PM
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Hi WV !
The stock sprockets are 15/43. This gives you about a 3 to 1 ratio. Changing one tooth on the front is equal to changing 3 on the rear. I am not sure but a 13 on the front may cause interference issues with the swingarm. Most guys go to a 14 on the front for offroad and are happy. If I remember correctly a one tooth change on the front is about 500 rpm difference for the same speed in top gear. Some guys have a 16t for freeway driving and a 14t for offroad and swap them as needed. It takes about 15 minutes to swap one out. Front sprockets are much cheeper and easier to swap out than rears!
Check out the bike gearing calculator by tom Schmitz in the "2008+ KLR650 Wrenching & Mod Questions" found in the main forum.
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Last edited by justjeff; 09-20-2013 at 10:54 PM.
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post #3 of 35 Old 09-20-2013, 11:44 PM
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As always a good answer from Jeff. I would try the 14 on the front. Myself I run a 16 all the time and it works for me although the stock 15 may start going on again when I hit the back roads.

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post #4 of 35 Old 09-21-2013, 01:37 AM
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Originally Posted by justjeff View Post
If I remember correctly a one tooth change on the front is about 500 rpm difference for the same speed in top gear.
I think you'd have to specify the speed to calculate the difference in rpm a sprocket tooth change would make.

Let's say at speed, "X" mph, the engine turns 4,000 rpm with a 15-tooth rear sprocket.

Change to a 14-tooth, and it will turn at 4,287 rpm at the same speed.

Change to a 13-tooth, and the rpm will be 4,616 rpm; again, at X mph.

At 5,000 rpm it runs, stock, at Y mph? With a 14-tooth front sprocket, expect 5,367 rpm; with a 13-tooth, 5,770 rpm.

Formula: New rpm = Old rpm X 15/(New Countershaft Teeth Number)

If these figures are in error, either I've made a mathematical mistake, or I don't understand drive ratios, or both!

A smaller front sprocket shouldn't cause any mechanical interference (although a larger one (say, 17 or more teeth) might pose some clearance issues), I'd think; some minor additional chain wear may result from the tighter radius of a smaller sprocket; and if you loose too many teeth, conceivably, you could run out of chain slack adjustment room with a too-long chain (cut some links to solve that problem).

Welcome, indeed, wv stump jumper! I've jumped a few stumps myself, at your Hatfield-McCoy Trails; and plan to jump some more at the Shenandoah 500 next month!
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post #5 of 35 Old 09-21-2013, 09:57 AM
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Thanks for the kind words klr4evr! As for YOU Damoclese.....367rpm could be considered "about 500rpm" as stated in my post!!

Think....Canada Power!....justjeff

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post #6 of 35 Old 09-21-2013, 10:12 AM
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RPM = Revolutions Per Meter?

Gray-haired riders donít get that way from pure luck.

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post #7 of 35 Old 09-21-2013, 10:19 AM
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Originally Posted by justjeff View Post
As for YOU Damoclese.....367rpm could be considered "about 500rpm" as stated in my post!!
Your approximation (367 to 500 rpm) may be defensible, justjeff; however . . . you neglected to specify a SPEED, when you generalized, ". . . one tooth change on the front is about 500 rpm difference for the same speed in top gear."

The difference isn't "about 500 rpm" across the board, the "delta" depends upon the speed of the vehicle.

At a certain speed, the difference is EXACTLY 500 rpm. But, the "about 500 rpm" is not CONSTANT, from an off-idle crawl, to top speed.

How about, "One tooth change on the front is about 500 rpm difference at highway speed in top gear."

Alas; I fail to communicate. Again!
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post #8 of 35 Old 09-21-2013, 10:49 AM
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Actually you sometimes communicate reasonably well Damoclese but you often miss the point in your eternal quest for utter precision. I can calculate the gear ratio/sprocket change results to the nth decimal place too but for the purpose of the example it is irrelevant.

Good one Flash!! Just in mud and $n0w!
Regards....justjeff

It's not a Tractor....It's a LOCOMOTIVE!! Chugga Chugga
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post #9 of 35 Old 09-21-2013, 11:27 AM
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Oh, and just to get back on track wv stump jumper....

Just get a 14 and a 16 tooth and change them out to suit your riding. Easy and cheap enough, I'm using the Sunstar brand.

Gray-haired riders donít get that way from pure luck.

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post #10 of 35 Old 09-21-2013, 11:39 AM
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You will also want a locknut for the sprocket so you don't have to mess with the bendy tab lock washer every time you swap sprockets.


http://www.eaglemike.com/Prevailing-torque-nut-PTN.htm

It's not a Tractor....It's a LOCOMOTIVE!! Chugga Chugga
Woooo WOOOOO!!!!!
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