XT660 Low high speed.

pilleway

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Hi, my XT660 has a low high speed, I do get about 90-95MPH at high RPMS, the machine has good torque and I see it can help using that torque to get some additional higher speed for cruice ahd probably improve fuel economy and get lower rpms at higway speeds, for that matter,I`m looking to replace the front sproket from 15 teeth to 14 or even 13, and keep the rear sprocket as it is (45teeth), would someone see any problem? Should I get by sets the sprockets?
Thanks in advance for any comment / suggestion or advice.
Have a nice weekend.
 

Sierra1

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IIRC, my son did something similar to that to his KLR, for the same reasons. I'm pretty sure he only changed the front sprocket. I cant remember how many teeth he reduced.
 

Jlq1969

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If you count the teeth of the pinion and the teeth of the crown, it is easy to calculate the percentage of change that you will get ... but first check if there is enough space between the pinion and the housing to fit a larger pinion
 

Jlq1969

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Pinion0/crown0 = R0
MPH/(RPM/1000)= X
———————————-
Pinion1/crown0= R1
(R1- R0)/R0=%
———————————
(1+%) . “X”= increase in speed at the same revolutions
 

Don in Lodi

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My memory says one tooth up front is almost equal to five teeth in back.
 

Jlq1969

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15/35 = 0.428
16/35 = 0.457
———————-
15/33 = 0.454

For example and for these specific relationships:
{(0457-0.428)/0.428} x 100 = 6.77%
then, at the same rpm and in the same gear, the speed would increase by 6.77%, by increasing 1 tooth on the pinion or decreasing 2 teeth on the crown
 
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pilleway

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Jlq1969, Thanks for the information regarding on the calculation for an estimated speed gain.
I did look in to the area of the pinion and there is space for a larger (1 tooth), the problem is to see if there is a 16 tooth or a less tooth crown, that is going to be my next homework.
Thank you very much.
 

Jlq1969

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Jlq1969, Thanks for the information regarding on the calculation for an estimated speed gain.
I did look in to the area of the pinion and there is space for a larger (1 tooth), the problem is to see if there is a 16 tooth or a less tooth crown, that is going to be my next homework.
Thank you very much.
however, if at your normal cruising speed, the RPM is at 80% of the red line …… you shouldn't worry.
 
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