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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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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.
Welcome to the Forum!!
Regards....justjeff
 

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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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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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Thanks for the kind words klr4evr! As for YOU Damoclese.....367rpm could be considered "about 500rpm" as stated in my post!! :wacko:

Think....Canada Power!....justjeff
 

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RPM = Revolutions Per Meter? :pot:
 

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As for YOU Damoclese.....367rpm could be considered "about 500rpm" as stated in my post!! :wacko:
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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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!:canada-flag-14:
Regards....justjeff
 

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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.
 

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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 appreciate the compliment, justjeff, but . . . fear I failed in this instance! :)

I never sought "utter precision," the "about 500 rpm" estimate is no issue with me.

Instead, I tried to point out that the difference in rpm depends upon the speed of the bike.

I think, "One tooth change on the front is about 500 rpm difference at highway speed in top gear" qualifies the relationship more fully, but that's perhaps just ME.

Regrets for any offense given; no contradiction intended.
 

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Get the grunt first then gear it.

I have a 14T stock 15T and 16T. I find the 14 makes 1st gear useless, your out of it to quickly on the street, engine rpm way to high in top gear and there is no real gain off road. The stock 15 is okay but at high way speeds the bike is buzzy and feels like it's work to hard. Off road first gear your ether to fast for first but to slow for second.

What works for me is first get more grunt. On your next valve check do the MC mod. Advance the exhaust cam one tooth. If you do nothing else, this is the biggest power up grade that you can do short of a big bore kit. Pipe, jetting, airbox mod anything.

I use a 16 tooth, for the street it dropped the rpm's 500 in top gear. Took the buzz out of the bars and the engine doesn't feel like it's working so hard. For off road first gear is more usable with larger power rang. I don't feel like I'm slipping the clutch anymore or less then the 14 or 15 at low speed. Just shifting a lot less.

The key is get more grunt, it's free power, anything else you do will be a so so improvement. No down side, I get 48 to 51 mpg quicker throttle response and more low end torque. If for some reason you don't like more torque and quicker throttle response you can always go back to stock cam timing.

Get the bike running the way it should first, then make a gear change. Drill out idle mix plug, run the screw out 1 and 3/4 to 2 turns out, (Free) 22 cent mod (22 cents or less) or KLX needle and jet. (40 bucks + -) If you choose to do nothing else the MC mod is a must at your valve inspection. (FREE)
 

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Advance the exhaust cam one tooth. If you do nothing else, this is the biggest power up grade that you can do short of a big bore kit. Pipe, jetting, airbox mod anything.
Fascinating, kilowatt!

How much additional power results from advancing the exhaust valve timing?

Is any data available from before-and-after dynamometer tests of this modification?

Further, is the additional power available across the entire KLR650 rpm spectrum, or are the profiles of the torque/horsepower curves altered by the change?

Thanks for sharing your experience.

-----------------------------

I'll pose a couple of questions for general discussion:

The valve timing varies, generationally, between KLR650s--are performance gains similar or equal between Generations 1 and 2? Anyone tried it on a Generation 1?
 

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Yes there is hope this link helps. I have done Gen II bikes with very good power increase. Gen I bikes, MONSTER power increase. Power wheelies on tap.

http://www.klr650.net/forums/showthread.php?t=109196&highlight=free+power

Reading through that thread I see coments about slight power increases (along with power signing off >6k rpm). Nobody mentions "monster" type increases.

The way I understand this chart green is stock. The increses are about 5% in the 3.5-5.5k range.




Of course people were claiming power increases with a PCV valve. Coment line open Damocles...
 

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Of course people were claiming power increases with a PCV valve. Coment line open Damocles...
I hold my tongue, er, KEYBOARD, Spec! :)

Cam timing conventionally is expressed in crankshaft degrees; one cam sprocket tooth subtends 15 crankshaft degrees.

Kawasaki sport V-twin ATVs had cam timing advanced 10 crankshaft degrees from essentially the same engines in utility ATVs.

Automobiles with variable cam timing advance valve timing at higher rpm.

As to the sharp cut-off around 6000 rpm, if a valve opens sooner, it closes sooner. This cut-off may result from reduced scavenge period at high rpm with the exhaust cam advanced; my speculation only.

Regardless, congratulations to those who find advanced exhaust valve timing more optimum than stock.

Now, back to the power gains from the PCV valve mod . . . :)
 

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How many teeth do you have

You can analyze it to death or do it. There were 30 people at the tech day in Flagstaff. 20 or so did valves and MC mod. All glad they did. We had the one and only Eagle Mike there with a case of Doo Hickies and springs. Everyone left with a bike that ran better.

You just have to figure out what kind of rider you are. A 14 tooth short shifting rev jockey. :bike: 15 tooth, I'll just leave everything stock and be happy, :sleep: or a 16 tooth I'll give it a try and take that jump, adventure rider. :thumb:

Do I smell chicken....lol :think1: After all it's on the internet it's got to be true. :pC fail:
 

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Alright boys here's the deal.....My '11 modest power gain to the point that I question the benefit. My '03 I can wheely with 1/3 throttle on flat ground in first gear. NO PROBLEM!!
The only other difference in engine mods is the "03 has a lexx exhaust. Both have A KLX needle kit, Uni filter, desnorkle mod, drilled slide and 2 turns out on the idle mix screw. Both get 50mpUSg milage. Both bikes have 15/43 sprockets.
So where is the big difference? Surely not the exhaust!! I haven't heard of massive power gains on a klr by adding an exhaust. The '03 didn't pull this hard before I advanced the cam. The exhaust was on before that. I have, by accident, hit a good combination.

I think people have missed a big point in doing the MC mod. When you adjust the cam timing by advancing the cam one tooth you still have no idea where it started or where you have moved it to. You could be advancing it TOO FAR. You could be going past the sweet spot. Or NOT ENOUGH. How do you tell. Just moving things by trial and error is a guessing game. If you don't know where you started and where you ended up you will not be able to replicate the results.

This winter I plan to DEGREE the camtiming on both bikes and compare where they started to where they are now. I will see how they compare to each other as well. The '03 definitely pulls harder. Where are it's cams set compared to the '11? Time will tell.

Eagle Mike mentioned building an adjustable cam gear and trying different settings on the dyno.....THEN POOF!! no more mention from him on the .net thread. He seems to have clammed up on the subject. Has anyone else heard or seen any further results from him?

Willys as well has disappeared. He was working on an adjustable cam gear too. Maybe he partnered up with EM?:stickpoke: Coincidence? Maybe They got too close to unlocking the massive power secrets of the KLR engine and the Kawasaki Mafia got them!! If I disappear too don't mess with KLR cam timing alone.....

Regards....justj________________
 

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Talking to Eagle Mike at the tech day, he is still working on adjustable cam gear. But his attention has been diverted to the big bore stroker kit and EFI. The 7.5 degree one tooth advance on the exhaust seem to be close to optimum. According to EM's dyno test. Adjusting 1 or 2 degrees + or - of that may not make it a sellable item. I'm just speculating but when people know all you have to do is this simple mod. Why buy something you don't need. If you like the r's over 6,000 stick with stock timing.

As far as not know were you started from, you start from stock timing marks.

Back to the original post before the MC mod I tried 3 gearing changes. Always came back to the 16. In Arizona we don't have a lot of mud or high altitude were the 14 and 15 may work best. The MC mod made the 16 tooth better. Steep grades that I could only maintain speed in 5th, I can now accelerate. I have a lot of weight on the bike with loaded side bags, top box, tip over bars, center stand, added lights, bash plate and all the wind drag that goes with those things. The bike pulls well with camping gear or just a work mule. These are the conditions I ride and get 48 to 50 mpg's.
 
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