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Old November 9th, 2018, 11:49 AM   #1
Darksik
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A good front chain sprocket

Hi guys i have a problem, danno told me to get a JT front sprocket, but the sprocket don't fit on the bike, also somebody know what is the Stock sprocket teeth? and how many sprocket i can reduce or increase?

Because if bought the rear sprocket and chain, the rear sprocket is 45T and the chain is a 520, that is why i was asking the stock front sprocket teeth, and how many teeth i can reduce or increase, because i don't have more money to buy the rear and front sprocket.

My idea is to reduce RPM maybe 500 rpm from the stock
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Old November 9th, 2018, 12:37 PM   #2
Triple Jim
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First off, I'd contact JT and find out why it doesn't fit. I have a JT on my 250.

There's a good article on sprocket ratios here: https://faq.ninja250.org/wiki/I_want...nge_my_gearing
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Old November 9th, 2018, 12:54 PM   #3
Darksik
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Quote:
Originally Posted by Triple Jim View Post
First off, I'd contact JT and find out why it doesn't fit. I have a JT on my 250.

There's a good article on sprocket ratios here: https://faq.ninja250.org/wiki/I_want...nge_my_gearing
i bought the front sprocket on ebay and in the page, says it won't fit on the ninja 250r, but danno told me that sprocket fit on the bike
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Old November 9th, 2018, 01:48 PM   #4
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Hmmm...danno is usually right.

Adding 1T to the countershaft sprocket typically drops RPMs by close to 500.

Stock the front is 14T and rear is 45T.

Going to 15/45 will drop the revs, but cost you on acceleration.
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Old November 9th, 2018, 02:02 PM   #5
Darksik
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Originally Posted by jkv45 View Post
Hmmm...danno is usually right.

Adding 1T to the countershaft sprocket typically drops RPMs by close to 500.

Stock the front is 14T and rear is 45T.

Going to 15/45 will drop the revs, but cost you on acceleration.
i know i have to open the throttle a little more, but i want to ride on highway and i don't want the bike go to rev, because i have a "chinese" exhaust akrapovic "replica", and int 9k rpm hear a little forced :/
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Old November 10th, 2018, 02:29 AM   #6
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the ninja 250 engine powerband is meant/designed to run at high rpm. why would you want to change this? i have el cheapo exhaust on both red and green and always run 9000- 12500 rpm. the engine can take it. the stock gearing ratio is not that bad. 70-80 mph around 9000-10500 rpm. just my opinion. is ya want lower revs buy something else.
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Old November 10th, 2018, 02:13 PM   #7
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Quote:
Originally Posted by Darksik View Post
i bought the front sprocket on ebay and in the page, says it won't fit on the ninja 250r, but danno told me that sprocket fit on the bike
I buy same 16t sprocket and it fits on my bike: https://www.ebay.com/itm/392130730515
Their chart shows it fitting 2008-2009 EX250J. Not sure why not later years as 2008-2012 is the same.

There's also this one which shows as fitting all new-gen 2008-2012: https://www.ebay.com/itm/362446119559

Post picture of what part doesn't fit and why. Might need an extra washer.

Last futzed with by DannoXYZ; November 10th, 2018 at 05:17 PM.
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Old November 11th, 2018, 12:57 PM   #8
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Depending on the make, not all 16t sprockets fit on our 250's. Some need a washer, some need to be flipped "engine side" and others will not fit at all.

Why not just run a 15 in the front and something else in the rear to get the same ratio and keep life simple? Or am I missing something?
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Old November 11th, 2018, 08:25 PM   #9
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I like the lower than stock sprocket ratio on my 250. If you like the stock setup, more power to you. As long as you can downshift and get the revs up, the lower ratio won't hurt acceleration. It's really off the line that it changes.
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Old November 12th, 2018, 09:29 AM   #10
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I ran a 16 tooth for a few miles. c/sprocket cover wouldn't fit correctly, so left it off. finally changed rear sprocket and went to 15t c/sprocket.
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Old November 18th, 2018, 12:18 AM   #11
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Quote:
Originally Posted by DannoXYZ View Post
I buy same 16t sprocket and it fits on my bike: https://www.ebay.com/itm/392130730515
Their chart shows it fitting 2008-2009 EX250J. Not sure why not later years as 2008-2012 is the same.

There's also this one which shows as fitting all new-gen 2008-2012: https://www.ebay.com/itm/362446119559

Post picture of what part doesn't fit and why. Might need an extra washer.
Sorry for the late reply but i can't find some picture to see the front sprocket until today, but i don't know why but the sprocket and chain won't fit, because the clutch cover is big, and when you put the chain, the sprocket cant move, here is a picture, i hope you could understand the yellow line is the chain and the red line is where the bike won't fit for the clutch cover, and the red circle is the "sprocket"
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Old November 18th, 2018, 02:25 PM   #12
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Did you have chain ends connected before installing sprocket cover?
Did you have chain tension adjusted at swing-arm before installing sprocket cover?

Take and post photo of just 16t sprocket installed.
Take and post photo of chain wrapped around 16th sprocket.
Take and post photo of chain wrapped around 16th sprocket after chain-ends have been connected.
Take and post photo of chain wrapped around 16th sprocket after chain-tension have been adjusted at swing-arm.
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Old November 19th, 2018, 01:51 PM   #13
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Is the sprocket free in the engine side??

I think if it is placed inverted it will touch the engine (i hope I am explaining my self)

Attached is the image with the sprockets I am using now in case de part numbers help. 15T in the front with no problem. Hopefully you find a solution for your 16T

Regards
Attached Images
File Type: png Screen Shot 2018-11-19 at 2.47.05 PM.png (52.6 KB, 0 views)

Last futzed with by MauR; November 19th, 2018 at 01:55 PM. Reason: added a comment
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