Yo,

So my 650R is all stored away which makes me sad but getting ready for the plans that I have for the sexy beast haha!

Since it is stored away I don't really have the oppurtunity to look at it so am trying to determine the stock sprocket sizes (front & rear) including number of teeth.

I would like to upgrade my sprocket and chain for better acceleration but can't make a decision on number of teeth for each until I know what the stock is.

Can anybody help?

Also, I do not have much experience when it comes to changing your sprocket sizes and what that does to the bike in terms of performance. Logically the best set-up would be a 17 tooth front and a 39 tooth rear. This would give the best gear ratio out of all the options available but is this too extreme?

And does the sprocket size (diameter) change with number of teeth?

Any feedback would be appreciated. Thanks!

 

Rear is 46 tooth
Front is 15 tooth
thats on an 06 you didn't say what year yours is I'm guessing they are all the same
If you want more acceleration you need to lower the gearing in other words a smaller front or larger rear sprocket. The easiest and cheapest way is to drop a tooth on the front, in other words go to a 14. If you don't like it your not out much money. Dropping 1 tooth on the front is roughly the same as adding 3 teeth on the back.
You can of course increase the number of teeth on the rear and lower the gearing by smaller amounts however you will more than likely need a longer chain. I went from a 42 tooth to a 45 tooth on my KLX250 and had to use a 108 link chain as against the OEM chain of 106 links.
Lowering the gearing will raise the engine revs for the same road speed and may reduce your top speed.
A 17 tooth front is unlikely to fit under the sprocket cover and even if it did running a 39 rear would make the gearing so high I doubt the bike would be usable over 4th gear, the stock gearing of 15 / 46 gives a ratio of 3.067 the 17 / 39 ratio is 2.29, considerable difference.
Yes the diameter of the sprockets change with the amount of teeth, more teeth larger diameter.
Hope this helps

 

Stock is 15/46.

14/46 is a good compromise to sharpen up the bike without losing too much top speed. 14/48 is about as far as you want to go if is 14/46 isn't enough.

Going too small on the front sprocket increases chain wear.

17/39 is going in the wrong direction and will be massively overgeared without a streamliner shell.

The sprocket diameter changes with the number of teeth.

Rob

 

when i bought my bike the previous owner had put down 1 front and up 2 in the back
so it was 14/48
it was very snappy, too snappy for me.
i put the stock rear sprocket back on and love it.

14/46 is good for me. much smoother.

aslo the speedo was off about 15% so a speedohealer had to be plugged in,
also highly recomended.

 

My current ride is a 2007 650R (I LOVE THIS BIKE!!!), and I run a 17/30 sprocket setup that's about 1.5x over stock gearing. I made a 6-sided speedo sender cam out of a M20 trailer axle nut to replace the 4-sided sender (in order to have a near-perfect speedo calibration). As for the acceleration, it's a bit like taking off in 2nd-3rd gear, but the factory gearing of pretty much every Ninja is way under-geared. I've had over a dozen Ninja 500's geared similarly, and I've beaten less experienced "street racers" (with their 4-cylinder hyperbikes) to the next stoplight MANY TIMES. While they're busy getting all tangled up with their rapid and constant shifting and clutching, I'm making my way down the road, and letting the engine do all the work in my very tall 1st gear and hitting over 50 MPH before I speed shift into 2nd gear (and pulling an accidental power wheelie from all the torque available there, and lifting the front tire off the ground for maybe 20-30 feet), as I typically leave them far behind in my dust wondering "how the hell that just happened"!... Add to that the fact that my engine might never wear out, due to the ability of cruising at freeway speeds of over 80 MPH @ under 4000 RPM while getting over 60 MPG, and hearing mostly just the wind rushing by... And with the exception of the 1st gear takeoff, everything else is simply gear selection as to "acceleration". Hobbling your gas mileage, engine life, top speed, and needing to hit 2nd gear before leaving the intersection by making your stock factory chronic under-gearing EVEN LOWER is a huge mistake in my view (over 50 years riding experience, and owned over 4 dozen different bikes). Hope that helps balance the view about "gearing/acceleration" typically seen in most rider forums. To summarize: acceleration depends on many things including "rider technique", but MOSTLY "gear selection" (with the ONE EXCEPTION of 1st gear, where "technique is EVERYTHING")...