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Rear Sprocket

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Mini_Stalk
Renault 5 Driver



Joined: 06 Jan 2007
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PostPosted: 23:39 - 14 Jul 2010    Post subject: Rear Sprocket Reply with quote

Hello i am thinking of getting a 3 tooth less sprocket for my yamaha sr 125 but as i understand it, it will lower my accelaration so would it be worth getting a different frount sprocket.

Thanks
Dave
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Paxovasa
World Chat Champion



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PostPosted: 07:13 - 15 Jul 2010    Post subject: Reply with quote

What do you want?

A smaller front or larger rear sprocket will give you better acceleration. If you do both then there will be no difference.

Fitting a smaller front sprocket will give you better acceleration and it might improve the top speed as you may be able to redline it in top gear.
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fiery tupp
Trackday Trickster



Joined: 24 May 2010
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PostPosted: 10:28 - 15 Jul 2010    Post subject: Reply with quote

If you need a new rear sprocket its best to get the standard size & then you can try either one tooth more or less at the front as these are only cheap & experiment , But with the yam sr 125( Ive just sold one) I wouldn't bother theres not much if anything to gain .
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Mini_Stalk
Renault 5 Driver



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PostPosted: 14:01 - 15 Jul 2010    Post subject: Reply with quote

i see, i just want a bit of a better top end cus it pisses me off stitting at 65 everyware.
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bacon
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PostPosted: 14:13 - 15 Jul 2010    Post subject: Reply with quote

Paxovasa wrote:
What do you want?

A smaller front or larger rear sprocket will give you better acceleration. If you do both then there will be no difference.


that doesnt make sense

small front = better acceleration
larger rear = better acceleration

If you do both, you will have even better acceleration, they will not cancel eachother out
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Mini_Stalk
Renault 5 Driver



Joined: 06 Jan 2007
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PostPosted: 14:26 - 15 Jul 2010    Post subject: Reply with quote

bacon wrote:
Paxovasa wrote:
What do you want?

A smaller front or larger rear sprocket will give you better acceleration. If you do both then there will be no difference.


that doesnt make sense

small front = better acceleration
larger rear = better acceleration

If you do both, you will have even better acceleration, they will not cancel eachother out


So if i get a smaller frount and rear it will give me better acceleration and top end.
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RussG
Scooby Slapper



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PostPosted: 14:38 - 15 Jul 2010    Post subject: Reply with quote

Yeah smaller front or larger rear.

If the front has to complete more whole revolutions than the rear you should (in theory) accelerate faster Smile
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Last edited by RussG on 14:41 - 15 Jul 2010; edited 2 times in total
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 14:40 - 15 Jul 2010    Post subject: Reply with quote

Mini_Stalk wrote:

So if i get a smaller frount and rear it will give me better acceleration and top end.


No. It is the ratio of the front to the rear that is important. Say you have 15:45 gearing. If you went to 14:42 (ie change you suggest) then the ratio is EXACTLY the same so the gearing is the same. No change in acceleration or top speed

All the best

Keith
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fiery tupp
Trackday Trickster



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PostPosted: 15:25 - 15 Jul 2010    Post subject: Reply with quote

So if you put a bigger sprocket on the front less acceleration setting off & at lower speeds & about half a mph faster top speed when you eventually get there in about mid august Wink sept if its wind is against you & if theres any hills on your route send us a xmas card Laughing
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bacon
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PostPosted: 15:36 - 15 Jul 2010    Post subject: Reply with quote

Mini_Stalk wrote:


So if i get a smaller frount and rear it will give me better acceleration and top end.


no its done in ratio's

14/42
15/45
16/48

for example are all the same, ratio of 3 (rear teeth / front teeth)

Higher the ratio, faster acceleration, lower top speed
Lower the ratio, slower acceleration, higher top speed

There are obviously other contributing factors, like the power of your bike and aerodynamics etc, that mean you cant get a cg125 say doing 120 despite the gearing allowing it

Cheers

Mike
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benlooker
Two Stroke Sniffer



Joined: 03 May 2009
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PostPosted: 18:49 - 15 Jul 2010    Post subject: Reply with quote

Hi, i kind of understand the theory behind how changing sprockets can alter acceleration/top end.

I am ready for a new chain and sprocket set for my Honda XL 125 and have been looking at getting a different set ie front -1 and rear +2 to increase the top end.

My bike struggles to hit 65 and is revving very high at 60. Would altering make a noticeable difference in top speed?

I would like to be able to hit 70 and sit at 65 comfortably, or higher if possible but not expecting for anything unrealistic.
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 19:02 - 15 Jul 2010    Post subject: Reply with quote

Hi

Smaller front or a larger rear will LOWER the gearing. Lower gearing = more revs for the same speed. If you are running out of revs then you need higher gearing so a larger front or smaller rear sprocket.

However an XL125 is unlikely to go much quicker anyway. Not much power and a flying crucifix riding position to maximise wind resistance.

All the best

Keith
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Mini_Stalk
Renault 5 Driver



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PostPosted: 21:08 - 16 Jul 2010    Post subject: Reply with quote

Thank you all for you help Smile Smile
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