12x47 or 13x50 Final Drive for 220?

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Jun 29, 2007
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#1
I need more low end for my 240 lbs in the tight and steep moutain single track I ride here in Utah at times. Should I just put a 12 tooth front sprocket on and keep the 47 tooth rear or should I go with the stock 13 tooth up front and a 50 in the rear? I found where it was advised to change to a 12 tooth up front for more low end but then recommended going with the 13x50 if you were replacing a chain. What is the advantage?

It seems to me that it is easier just to change front spockets depending on riding conditions.

Thanks in advance for your input!
 

dirt bike dave

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May 3, 2000
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#2
In theory, the 12 tooth countershaft is harder on the chain than a 13t. So chain and sprokect life would be better with a 13t than a 12t. Howver, you might need a longer chain to run 13/50 or 13/51.

If your chain is in decent shape, just put on a 12t. It is much cheaper to experiment with this. If you like the change, you can go to 13/50 or 13/51 with a longer chain next time you need to replace the chain and sprockets.
 
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#3
I agree with dirt bike dave above. The problem with the larger rear sproket is you need a longer chain and many have chain guide problems. You will like the 12t sproket and you might want to consider a flywheel weight. If you are riding at high elevations, your jetting will be critical to your enjoyment. Cheers John
 
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#4
Thanks for the input. I installed the 12 tooth and it seems to be the ticket for the low end enhancement. I will try this for a while and possibly lean out my pilot jet some. I currently run my needle in the leanest position, a 38 pilot (and it is just a tad rich at 8500' elevation) and a 143 main.

Thanks guys!