Front sprocket chain 420 PBR for Honda CRF 70 F4 04-11

By choosing the ratios, 1 front sprocket cog is equal to about 3 rear sprocket cogs (the exact ratio is given by: number of rear sprocket teeth / number of front sprocket teeth).
The above stated, ratios have to be chosen in a way that a max. difference of 2 cogs is not exceeded. This way, you can always keep the same chain length. The Kawasaki ZX-10R Ninja is an exception: a rear chain with over 1 tooth more than the stock one cannot be used, since length of stock chain will not allow that. Remember that if you want more acceleration you have to mount a rear sprocket with more toothing, or a front sprocket with lower toothing. Ratios have to be necessarily and exclusively chosen by yourself. It is usual to mount a rear sprocket with 2 teeth more than the stock one, but that is however a medium choice which does not mean to be satisfying to everybody.
In a circuit, generally the right final ratio will be that allowing to achieve, at the highest gear, about 200 rpm more than the max power rate, always staying 200 / 300 rpm under the maximum rate the engine can reach. This way, you can take advantage of the trail of the driver who is preceding you.
Choosing the final ratio, remember that the bigger it is, the more the acceleration will be. But if it is too big, you will lose speed. If on the contrary the ratio is too small, you will lose acceleration and will not manage to reach the maximum speed.

If your final transmission has exceeded 5000 km, we advise not to change only one of the three components, but to change them altogether (chain,rear and front sprockets). This, because final transmission would otherwise deteriorate in very few kilometres.

For the best working and longer duration of the transmission, it needs to be cleaned and lubricated every 1000 Km at least, using our specific cleaner and lubrificant for chains that you find here.

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