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Going down in teeth rear sprocket?

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So i am thinking about doing some of the local arena cross races in a few weeks and noticed that a lot of my buddies who were racing last night we going down in teeth with their rear sprockets. Im not sure what my rear sprocket is, but i know its probably a 50. One thing i want is so that my first and 2nd gear arent so fast. It seems anything after 2nd pulls harder and doesnt rev as quick which is what i like. Would going down to a 48 tooth rear sproket help spread 1st and 2nd out a bit??

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48 is stock, so the bike has no problems pulling it.

If doing very tight arenacross style riding you could maybe get away with a 47 and staying in second gear for 95% of the track.

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For AX you want a bigger back sprocket to give it more bottom.

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so... witch is it one comment is 47 and the other is saying bigger?

does some one knows or can explain in plain English the gearing principles

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By adding teeth to the rear sprocket you will increase the ratio and make the bike slower than it is now at the same rpm. The bike will have more low end and rev quicker. It really depends on the track and how you like to ride. When D-K suggested going down on the rear it was to make 2nd gear faster and maybe you would not have to shift as much.

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I would run a bigger back sprocket so u have the bottom end and quick rev to clear those jumps. I know the supercross guys run bigger rear sprockets for the same reason. They need that quick rev and snappy bottom end on those tight tracks. I run a 50 in the woods for my HS races. I'm gonna move up to a 51 next sprocket bc I like the real snappy power. Id do the same for a AX or SX track too...

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You will have to test for yourself to find a gearing you like. With a 51 tooth you can basically forget about the first 2 gears and start from 3´rd.

48 is stock and suits outdoor motocross. 49 is also good for this and let´s you carry third gear through most corners, to save a shift on the exit of the turn.

For very tight tracks, most people LOWER the gearing by putting on an even BIGGER sprocket, like a 50 tooth. This will add punch, but forces the need to shift more. Some people like it, some do not.

On a tight track with almost no high speed sections, staying with 48, or even going TALLER to a 47 could let you stay in second gear. Even for the start. And wide open in second gear the bike will clear most big jumps anyway, even those right after corners.

It´s a balance thing. You want to find yourself in third gear as much as possible as a rule of thumb though.

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You will have to test for yourself to find a gearing you like. With a 51 tooth you can basically forget about the first 2 gears and start from 3´rd.

48 is stock and suits outdoor motocross. 49 is also good for this and let´s you carry third gear through most corners, to save a shift on the exit of the turn.

For very tight tracks, most people LOWER the gearing by putting on an even BIGGER sprocket, like a 50 tooth. This will add punch, but forces the need to shift more. Some people like it, some do not.

On a tight track with almost no high speed sections, staying with 48, or even going TALLER to a 47 could let you stay in second gear. Even for the start. And wide open in second gear the bike will clear most big jumps anyway, even those right after corners.

It´s a balance thing. You want to find yourself in third gear as much as possible as a rule of thumb though.

I am going to check the sprocket teeth amount cuz the guy i bought the biek from put a renthall sprocket and chain on it. Not sure if he kept it at stock 48 teeth. Ill have to check. Cuz it does seem like basically 1 through 2 revs out way to quick and then 3rd 4th and 5th pull well and dont rev out nearly as fast.

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Just think about an old 10 speed bicycle. The smallest sprocket on the back with the big sprocket on the front was for long distance, top end and going down hills. The biggest sprocket on the back with a small sprocket on the front was for short distances and low end torque, hill climbing and wheelies. If this makes it easier to understand.

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Heres the thing.. IMHO in arena cross you're going to want to go up on the sprocket 52-54t.. the reason for this is because you ABSOLUTLY do not want to hit neutral. by going higher in the sprocket you basicly make 1st and second gear un-useable but 3rd and 4th gear now become your grunt. If I remember right the ratio between 3rd and 4th is wider then 2nd and 3rd thus giving you a broader range of power.. vs going down to a 48t that would not give you as much range to work with and the possibility of sticking in neutral and well face planting into a jump.. But I do not race or ride that tight of tracks so I could be just wrong..

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What year is your bike? 2010 and back are 48 tooth stock. If it is a 2011, the stock rear sprocket is 50 tooth.

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What year is your bike? 2010 and back are 48 tooth stock. If it is a 2011, the stock rear sprocket is 50 tooth.

His signature says 2008.

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How will a 1 tooth larger/smaller front sprocket affect gearing? I've heard 1 tooth on the front equals like 3 or 3.5 on the back?

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How will a 1 tooth larger/smaller front sprocket affect gearing? I've heard 1 tooth on the front equals like 3 or 3.5 on the back?

Larger does not physically fit, and smaller would chew up the swingarm real fast. And gearing would not improve.

But yes, it would make that kind of difference.

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Larger does not physically fit, and smaller would chew up the swingarm real fast. And gearing would not improve.

But yes, it would make that kind of difference.

If thats the case then why would they sell sprockets plus or minus one? And I'm talking about an 07 kx 250f by the way

Edited by rider119

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