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dazzzaa
Nitrous Nuisance



Joined: 22 Apr 2011
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PostPosted: 08:50 - 14 May 2011    Post subject: top end Reply with quote
i,ve gone throu the threads and cant find the one i started sorry so heres a new one.

i have a chinese 125, THE CBR COPY, and i want a little more top end out of it as im traveling 27 miles on a dual carriageway to work, someone mentioned a bigger front sprocket which i am now able to achieve, suppoesedly 15 tooth at the moment and i want to go up to a 17. will i need a new chain or can i adjust the back wheel and which sprocket can i use? (off cbr125 or similar)

is there a certain type?

thanks all Very Happy
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Digit
Scooby Slapper



Joined: 22 Aug 2010
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PostPosted: 15:37 - 14 May 2011    Post subject: Reply with quote
Forget it! It doesn't work!
If it did we would all use engine sprockets as big as dustbin lids. Rolling Eyes

Roy.
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Frost
World Chat Champion



Joined: 26 May 2004
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PostPosted: 15:42 - 14 May 2011    Post subject: Reply with quote
Well the gearing on a bike is a compromised between acceloration and top speed. This bike is limited in top speed by engine power not gearing, so going up a tooth on the front won't raise top speed, but it will reduce engine revs at the same speed.

Up 1 tooth should really be done with a new chain and sprocket set, but if you just want to try it, or the chain is new, or you just don't care you can do it with just loosening the chain. So loosen it, change the sprocket, then just adjust the chain as normal.
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Im-a-Ridah
World Chat Champion



Joined: 20 Oct 2006
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PostPosted: 16:03 - 14 May 2011    Post subject: Reply with quote
dazzzaa wrote:
i,ve gone throu the threads and cant find the one i started sorry so heres a new one.

i have a chinese 125, THE CBR COPY, and i want a little more top end out of it as im traveling 27 miles on a dual carriageway to work, someone mentioned a bigger front sprocket which i am now able to achieve, suppoesedly 15 tooth at the moment and i want to go up to a 17. will i need a new chain or can i adjust the back wheel and which sprocket can i use? (off cbr125 or similar)

is there a certain type?

thanks all Very Happy


Simple guide.

1. Put bike on ebay
2. Sell bike
3. Buy 500cc commuter bike
4. Marvel at how your fast, cheaper to insure, more reliable bike gets you to work

Trying to make the bike do something other than going around town is just going to waste your money.
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Teflon-Mike
tl;dr



Joined: 01 Jun 2010
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PostPosted: 16:19 - 14 May 2011    Post subject: Re: top end Reply with quote
dazzzaa wrote:
i have a chinese 125, THE CBR COPY, and i want a little more top end out of it as im traveling 27 miles on a dual carriageway to work,


If its the bike we think it is, all the above is right, it looks like a CBR, but has a CG engine, and a badly made one at that.

Power = Speed x Force

Doesn't matter which way you cut the custard, to go faster needs more power, to over come the greater drag force at higher speeds, you can mess with gearing to get the peak power in the engine rev range better matched to the max road speed the power you have allows, but it will only make 2 or 3mph difference, and depending on the original gearing going UP may actually make the bike slower... they are often over geared to begin with.

Problem isn't gearing, and even if it was, it wouldn't provide the 10mph or more you need to comfortably stay with traffic on by passed & duel cariageways where people are regularly doing 70 or 80mph.....

Change your route to work, or get a different bike, (and most Learner Legal 125's chinese or not, will struggle to keep up with traffic on duel carriageways, regardless, so means moving up to bigger, non learner bike, basically) not your sprokets,
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prawny1
World Chat Champion



Joined: 28 Jun 2005
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PostPosted: 01:39 - 15 May 2011    Post subject: Reply with quote
DaFrostyOne wrote:
Well the gearing on a bike is a compromised between acceloration and top speed. This bike is limited in top speed by engine power not gearing, so going up a tooth on the front won't raise top speed, but it will reduce engine revs at the same speed.

Up 1 tooth should really be done with a new chain and sprocket set, but if you just want to try it, or the chain is new, or you just don't care you can do it with just loosening the chain. So loosen it, change the sprocket, then just adjust the chain as normal.


Altering the gearing to lower revs if done right can be enough to put you back into your peak power range allowing you to reach a higher top speed,

you may well not be abled to reach the rev limiter/red line anymore in top gear but power would have tailed off by then anyway, you will however be abled to maintain 60mph more comfortably as the engine will be at a more efficient rpm.
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Old Thread Alert!

The last post was made 14 years, 225 days ago. Instead of replying here, would creating a new thread be more useful?
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