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16 T Front / 42 T Rear Sprocket Mod

34K views 17 replies 14 participants last post by  wilfredo tabangcura 
#1 ·
Ya'll,

I have to tell you about the gear change I have made to my '07 KLR. This morning I finally got around to installing both the 16 tooth front sprocket and 42 tooth rear sprocket and what a great difference! 95% of the riding I do is on the highway; so I was looking for find the perfect road set up. THIS IS IT! There is no appreciable loss of grunt on take off and the top end RPM's is greatly reduced. At 4000 RPM I'm running about 65 mph, at 4200 - 70 mph, 4500 - 75 mph and almost 80 mph at 5000 rpms.
SO for you fellow KLR'ers if road riding is your cup of tea. Do this Set Up! You will love it! It took me a leisurely 45 minutes to do the whole change: drink some coffee, smoke on a cigar, listen to some tunes and I'm done. I took about a 60 mile ride just to check it out and I'll NEVER go back to the stock gearing! I haven't had a chance to check the gas milege, but there is no way it could not improve it over stock.
 
#4 ·
Chain wear issue

Great job Denny, lets us know how it works out after a couple months or so.

One thing to consider, keep an eye on your sprocket and chain wear. Whenever there are even toothed sprockets in the front and rear, and an even number of links to the chain, the same chain links are continually contacting the same sprocket teeth. This can lead to uneven wear and a short chain and sprocket life. This can be avoided if you 'rotate' the chain periodically.

Let us know how it goes.
 
#5 ·
16T Front/ 42 T Rear Sprocket Mod

Ya'll,

Thanks for the insight. But, I fail to see how running my bike at 3500 rpms to 4000 rpms is going to "ruin" my motor. That is the RPM Range that I run every day - in town and out on the highway. I will keep on eye on the "Even / Even" situation as far as chain and sprocket life are concerned. If I were "lugging" the motor - yeah... but no way is the set up I'm running going to harm any component of my engine. In fact, it can't help but EXTEND the life of my motor.
 
#6 · (Edited)
The best thing that can be done for a KLR650 piston, wrist pin, and rod is not to overload or lug them by over gearing the motorcycle's final drive ratio.
Also, the KLR650 doens't exactly have the most efficient combustion chamber... being 1980's technology. Some modern bikes actually have two sparkplugs per cylinder and therefore are more efficient during the power stroke.
Over gearing won't usually translate into better mileage because you will either be lugging the engine, or you will be forced into lower gears more often.
 
#12 ·
mild seizures do sometimes happen. minor scuffing of the piston as opposed to major metal transfer. I have seen it many times over the years.
I never heard of taller gearing causing it though. could have been a variety of other factors to cause the failure of the "guy on craig's list"

taller gearing/lower rpm brings on conditions (called lugging) condusive to detonation which will damage engines, but higher rpm, less throttle, higher fuel octane, etc will stop the detonation. which means downshift rather than more throttle.
I assure you taller gearing will net you better fuel mileage with proper technique. I do wish my KLR had a 6spd box rather than 5.
I have already ordered a smaller rear sprocket. but my catalogs only list 15t oem replacement fronts.
I would like to know what brand of 16t countershaft sprockets folks are using on 08 klr's.
 
#14 ·
#13 ·
I found this thread today I know it's old but just wanted to say. I have a 04 klr 650. I do a lot of highway riding, I have run with a16 t on the front and a 40t on the rear for the last 6 yrs. as for lugging i still have no problem overtaking traffic at 100 km per hour that is our speed limit by just winding on the throttle no down change required. the motor sounds as sweet as the day I brought it brand new. I have been getting 400km and over before switching to reserve. Last week when I fuelled up I put in 19.5 lt for 435 km. sorry for the measurement but I am in Australia .
 
#16 ·
Old Thread / Valid Question


anruari,
Potentially Yes!

It primarily depends on your riding experience and deft control of the clutch lever and throttle. I used to do 2nd and 3rd gear starts on real dirt bikes. So for me it wouldn't hardly matter.

If you currently have any low speed issues with OEM 15-43 gearing, I wouldn't recommend higher gearing.
 
#17 ·
I'm one of the many who have converted to "street gearing" and there's never been an issue
other than running out of power in 5th gear as the wind resistance takes over.

It's nice not having to shift so often during commuting also. It takes simply running the revs a bit
higher before shifting so as to prevent lugging in the first place. Don't whack the thing wide open at 2800
rpms, etc. It's nice running interstate speeds at 5,000 rpms. It takes a lil' clutching offroading but first
and second gear still pull like a mule. Only in the technical gnarly stuff would I prefer a 14 or 15t up front.
My riding is street, and dirt roads/ atv trails. For those a 16 is fine. I'm currently on 15/42 as the 140/80
tire is taller on our narrow-ish rims. When I mounted it the tire got taller as the sidewalls were pulled in a bit.
Not much, but too much for a 16/42 AND the taller tire. I just about lost all the usability of 5th gear going that
tall on the ratio. At that point it became using 4th to get to speed, then only using 5th to hold the speed, but
having little to no acceleration. The 15/42/140mm is da bomb, and close to the 16/42/130mm final ratio.
The standard carb and airbox flow mods apply here to get the most usable power from what amounts to little
more than a large bore lawnmower engine. lol
 
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