12 tooth front sprocket

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Sep 17, 2003
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#1
Hi I am new to the forum. I have a 91 cr 125 that I use for tail riding. I would like to put 12 tooth front sprocket on. My dealer says not to because it is dangerous, that i will put the chain in to the case in three rides. I know that it will increase chain wear but is it that much. I thought I would ask you guys to see what you think.
joel
 
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#3
i have a 12 tooth on the front on a 99 rm125 (50 tooth rear) and its fine for trails.....i usually ride with a guys who have big trail 4 strokes and im fine with them (they just bug me because i have no kick stand)................and my chain is fine
 
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#5
merlin i wouldnt recomend it,12 tooth front 50 tooth rear,it will be trying to leap up in the air constantly withe no top end,nah,the bike is getting on a bit,the extra stress through harder exeleration something is gona give,but hey i wouldnt mind trying one of them 12s on me cr500,whhheey,houston we have a problem. good luck anyway.
 

motometal

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#6
the ONLY reason it would be a real problem is if the chain wears into the sliders on the swingarm.  On some Honda's, this is a problem, but i'm not sure on your particular year.  If it does, you'll know it if you keep an eye on it.
 

Jaybird

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#7
The smaller the CS sprocket is, the faster the chain, and consequently the sprockets, will wear out.
 

motometal

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#8
I'm sure you are right that wear would be accelerated, but enough to really matter in the big picture?  I doubt it.  If the end result on the gearing is what is needed to make the bike work, wouldn't the end justify the means?

Note: some bikes come stock with a 12 tooth sprocket
 

Jaybird

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#9
If you don't neglect your chain, then no...it may not be that big of a deal.
If you ride your chains till they snap and are happy with the time you get from them using minimum maintenance, then you may want to consider going bigger on the rear to gain a little time on components.
Some bike mfg's used a 12 and returned back to the 13. Others will too.
 

john stu

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#10
a friend of mine used a 12 tooth on his kx and when it wore out he went to a 13 with a bigger rear sproket to get the same gearing and he swears the bigger sprokets lasted much longer even the chain (same chain and sprokets before and after just different sizes).
 
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#11
i have an 11 on my old yz, best mod i ever made. but if dealer sand not too do it, i'd just get a bigger rear sprocket. i do have to shift alot since i added the 11/54 gearing. it was better at 11/52, as the 54 throws me up into the low rpm of the next gear higher, thus losing the effect of wanting more torque.
 
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#12
Thank you for all your help. I will try it next week end.
I wish I found this place sooner there is great information on here.
joel
 
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#14
The smaller diameter of the smaller sprocket will increase the sheeth resistance I think its called, the chain weares more becuase it has to bend around a smaller radious. The sprocket wears more because of this plus the wear is now distributed over fewer teeth wich ends up bing just over 12% I suppose if you go from 13 to 12 teeth. The CS now also turns more times per mile also. The chain would cause the rear sprocket to weare at the same rate as the chain more or less as it streaches. The only danger of putting it in the case I can see is that the smaller diameter leaves a gap between the chain and the guard that is there to keep the chain from doubling up in the event of a rear derailment, when the chain doubbles up is when they blow into the case, so depending on the gap, it is possible it COULD double up and put a new vent hole in the case, but as long as that guard is there its probably very unlikely, keep you chain adjusted and watch for those rock crevaces that like to derail your chain and you should be fine :) . I ride a 12 T on my WR most of the time and I have a 13 and 14 for it and the 12 has not caused me any problems at all.