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Gear ratio

77K views 92 replies 34 participants last post by  maverick9611 
#1 · (Edited by Moderator)
Has anybody changed the gear ratio from the standard factory sprocket? I have a 2008 KLR 650 and primarily ride it on the highway. I am thinking about changing the front sprocket so that the bike does not turn 4000 RPMs at 60 mph.
 
#2 ·
Did not say but I am assumming you want to lower the RPM's Go one tooth bigger on front. Stock is 15 so you want a 16.It is a noticable change in gearing. Some like higher gearing some do not. Depends on a bunch of variables so you must try it for yourself. Good news is the cost is really low. 20 bucks or so and it is easy to do.
 
#3 ·
I am trying to lower the rpms. It seems like I go thru the gears before I get out of the driveway. I live on the East coast of NC therefore the terrain is flat. I use the bike for short rides and enjoy riding speeds around 50 -55. I am thinking of changing the sprockets to 16/40 to obtain taller gears but I am not sure if the bike will be hard to get going in first.
 
#4 ·
Are you sure you are running stock gearing? 15/43 is stock. I would do the front sprocket 1st and see how you like it. Cheaper and has a noticeable effect. Going up one on the front and down 2 or 3 in the rear is quite a jump. I ran the 16/43 for about 12,000 miles and I am back to 15/43. I like it better. may even try 14/43.
 
#5 ·
I run a 16 tooth front with stock rear. I weigh a little over 200 pounds and took a 1200 mile trip (all highway) and heavily loaded. I had no problems even in the mountains the only time the 15 tooth will go on is in the woods.


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#6 ·
Just made a 2,000 miles trip to the south of Chile with mostly highway riding, but 1/3 on country roads both asphalt and loose gravel. Very frankly, before starting this trip I thought that the 16/43 was a necessary change, however after this trip, I think that the stock 15/43 is the best gear ratio overall to face highway, city and off road. Maybe if usage is ONLY highway, I think 16 front is a good option. Further than that, frankly not recommendable.
 
#8 ·
I replaced my chain before a trip to Baja a few months ago.

(http://vicurious.blogspot.com/2012/01/mexi-moto-day-1-outbound.html)

My '02 has 30,000 miles on it, 10,000 of which I put on it since I got it last year. I figured I'd do the "right thing" and replace both sprockets at the same time...and while I was at it, I decided to go with the 16 tooth drive sprocket to try it out.

The stock setup leaves me stressed out on the freeway. I prefer driving in the carpool lane, at least as fast as the speed of traffic. It feels much safer than being in any other lane with traffic zipping in and out all around me. The stock arrangement in such a situation had me looking at RPMs consistently well above 5,000, and left me feeling like I was asking far too much of the bike.

I was amazed what a difference one extra tooth made. At freeway speeds, it dropped 500 RPMs and made for a considerably more comfortable ride. Since the bike is my only means of motorized transport, the sad reality is that I do far more riding on the slab than I prefer. The 16 tooth sprocket is an undeniable asset on the pavement.

On the dirt, however, I am always missing the stock sprocket. There's no doubt about it, having that extra torque would be far preferable for anything beyond hard-pack or flat gravel...especially any kind of climbing.

So, I wonder...

Has anybody heard of changing out sprockets temporarily for different applications? When I installed the new chain, I cut it to length as it fit with the 16 tooth. Is there enough play in the rear axle adjusting screws that I could simply switch them out at will? I know it's warned that a chain and sprocket should wear out together, and be replaced together, but surely switching down to a 15 tooth now and again during extended dirt rides wouldn't be too detrimental to the chain...no?
 
#10 ·
Last summer I rode to Colorado for some off roading action, then to Montana for some mountain work, and then back to Houston to home for some honey -do action.. I carry a 14T 15T 16T and a 17T and change when riding conditions change. I run a stock chain and stock rear sprocket. Change over takes about 20min and some hand cleaner then back on the road. Lets you get the best out of the KLR. Just my 2cents Bye
 
#19 ·
Got a question on sprocket change. 2006 KLR, just removed the original sprocket. Looking to put on a 16t. I noticed on the original sprocket their was a plastic seal on the backside of it, that fits into holes on the 15t. The new 16t sprocket does not have the holes to use the seal. Should I insert a washer on the backside of the 16t sprocket? (for alignment purpose)
 
#20 ·
sprocket talk klr650

I have a 2007,and changed the front to a 16t,this is to much of a jump in my opinion and really makes 1st gear to high.I changed the front back to the stock 15t and went with a 42t rear instead of the stock 43t and this is much better .It lowers the rpms about 200 and maybe a bit more.The 16t front lowers them about 400 rpm.Just my experience.
 
#22 ·
Hi, I was thinking about buying a 2011 KLR 650. Most of my driving would be highway, around 70-80 mph. It has the original 15 sprocket. I don't want to be sitting at 5000 rpms for an hour straight, but I love this bike. Would this bike be able to handle all those highway miles? And what sizes should I change the sprockets to if I want to reduce the rpms?
 
#25 · (Edited)
EXECUTIVE SUMMARY: You'll get LESS "oomph" with 16/40, than with 15/45 (stock), 16/45 (popular choice), or certainly, 14/45, according to my calculations.

The 16/40 you propose multiplies torque far less than 15/45 (stock); considerably less than 14/45. The excessively high (low numerical) gear ratio likely could ultimately damage engine/bearings/etc. from excess lugging, especially when the bike is heavily weighted, seems to me.

Work the reciprocal division and compare the numbers. What does that mean? The reciprocal of 15/45 is 3.0; the final drive ratio of a stock KLR. The countershaft must rotate three times for the rear wheel to rotate once; the final drive ratio is 3.0. 14/45? Final drive ratio, about 3.2: countershaft sprocket must rotate 3.2 times for the rear wheel to rotate once. 16/40? Final drive ratio, 2.5--rear wheel rotates ever 2.5 countershaft revolutions.

Looking at a common mod, 16/45: Final drive ratio is about 2.8; yeah--rear wheel turns once in 2.8 countershaft revolutions. Your 16/40 2.5 drive ratio's pushing things, IMHO; suggest you check your calculator again.

One countershaft sprocket tooth corresponds to three rear sprocket teeth, considering stock gearing as a baseline.

DISCLAIMER: My postulations only; corrections, clarifications, and contrary opinions welcomed, as always! :)
 
#28 · (Edited)
I tried the 16 tooth front sprocket with the stock rear sprocket. It did reduce the RPM, but it didn't do anything else. It did not increase gas mileage. In fact I got less gas mileage. I think the motor would bog down more if I got into heavy mud or on a steep hill, but it has been a long time since I had it, so I can't remember.



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#80 ·
17



I have and love the 17 front and stock rear. I do highway and gravel roads and non town maintained roads.
It didn't do anything for better mpg;s
( no wind ) goes good will be happy at 80mph all day long.
( With the wind ) OH MY. Feels like a crotch rocket.
( Against the wind ) UUMMM??? It don't like it much. Still will hold a solid 70mph or more, but just hold throttle wide open. Don't even think about passing someone.
Im 5;11 about 170lbs, and with full helmet and large panires and crash bars, All that adds some wind resistance.
Had to trim the plastic cover a ltl, and no problems with the wires.
Probably around 8,000 miles on the 17, took 15 off around 1,000 or less.
The 17 isn't going to like off roading.
I do have a new 14 I should try out.
 
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