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Discussion Starter · #1 ·
Looking to maybe change to 15/38or39 sprockets. I am looking to cut down on vibration and up MPG without killing low end to much to get up to speed on freeway. Things anyone have tried and you results on mileage and torque would be appreciated.
 

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I have the 15/42 set up. I like but i wouldn't mind a little more for long road trips. On some of my trips i can be at 70mph running about 8K rpm. I have a 38T but the chain is too long. A 40 would fit tho but i haven't gotten one yet.
 

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Discussion Starter · #4 ·
Blue.thanks for the help guess I'm lacking. Unable to find search on forum. Please keep in mind I only have a mobile device to use.It reads different unable even see pics.
 

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A 15/42 or 15/43 set up is probably a optimal setup. You will still have a little power left in 6th gear to pull away without having to downshift, gain a little top end speed and still get good mpg on a stock bike with no mods (depending on how you ride). A 15/41 can be done with exhaust & carb mods comfortably. If going smaller to a 38 or 39 tooth rear sprocket stay with a 14 tooth front. If you travel a lot of hills 15/42 or 15/43 will do just fine with minimal downshifting. Your overall performance from the stock bike will change nicely with no more wasted horsepower. Whatever you decide to do...enjoy! If you are able to access the forum well, see the comments in General Tech / Speedometer testing and results.

I also use this speed table ( a mathematical calculator) to also calculate speed. I found it really similar to GPS speeds. Here is how to use it.
1. In the rear tire circumference drop down box click other and type in your rear tire circumf.
130/70/17= 75.917
140/70/17= 77.651
150/70/17= 79.382
150/60/17= 75.671
2. Type in your front and rear sprocket sizes
3. Type in your max. RPM u can maintain then click calculate and see your final speed.

http://ninja250.kingston.net/speed.html
 

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Razorback said:
Looking to maybe change to 15/38or39 sprockets. I am looking to cut down on vibration and up MPG without killing low end to much to get up to speed on freeway. Things anyone have tried and you results on mileage and torque would be appreciated.
i run a 16\45

plenty of top end 12k on tack at 95 now 11k on tack at 105 so...

i can drive comfortably on the highway 70mph without thinking... those chunks of aluminum are moving damn fast by my baby maker...

as far a torque goes, well i lost a bit but boosted mpg from about 65-70 to 70+ depending on how i drive..
 

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Damn Audacia, you must really go easy on that throttle. I get 55mpg... ALL THE TIME. he he.... I'm running 15/44 right now, and I gotta say, I think the 15/43 is THE PERFECT combo, EVER! (being overly dramatic)... Unless you're doing all kinds of "power mods" like X, then you're gonna need taller gearing to make use of all that extra power.... :D
 

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spooph said:
Damn Audacia, you must really go easy on that throttle. I get 55mpg... ALL THE TIME. he he.... I'm running 15/44 right now, and I gotta say, I think the 15/43 is THE PERFECT combo, EVER! (being overly dramatic)... Unless you're doing all kinds of "power mods" like X, then you're gonna need taller gearing to make use of all that extra power.... :D
eh i putt around but on occasion my bike sees the sunny side of 11k on the tack haha...
 

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Razorback said:
Looking to maybe change to 15/38or39 sprockets. I am looking to cut down on vibration and up MPG without killing low end to much to get up to speed on freeway. Things anyone have tried and you results on mileage and torque would be appreciated.
that config you might as well do a 16f with 45r itll be the same thing
 

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Discussion Starter · #11 ·
I'm currently trying 14/41.Seems ok uped mpg about 4 didn't hurt low end. My dealer will not change front bigger say its unsafe. After saving more might try 38.
 

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15 front is just fine, you're dealer is lying to you about a 15 front being unsafe, because a 15 front costs about $13, and a 38 rear costs about $40... They make more money on rear sprockets.... Put your foot down!
 
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