What sprockets size (teeth) should I get? I want something with a little more low wnd grunt but don't want to pop wheelies.

i would keep the stock rear and go one more in the front. not to much but a little off the go power.

No you wanna drop a tooth in the front not go up.

Increasing the front or lowering the rear will make the rear wheel turn more times per engine rev. Which gives you higher theoretical top speed but makes the bike work harder. An r6 can't push the bike hard enough to over come drag as it is.

Decreasing the front or raising the rear will make the rear tire turn less at the same rpm. The motor doesn't make anymore power when you alter gearing but it alters the speed at which the power is being used.

Example, (and these numbers all purely for the example and are not real) at 10k rpm your bike makes 100hp. In 3rd gear with stock gearing 10k rpm is 80mph. If you drop a tooth in the front, 10k in 3rd would be 70mph. If you raise a tooth in the front 10k in 3rd would be 90mph. The bikes still making 100hp, but 100hp motivating 600 pounds to 70mph is much more effortless than trying to go 90mph.

As far as the wheelie thing goes, even if you alter gearing rather drastically like mine... down 1T in the front and up 2T in the rear, after 100 miles you get used to the new throttle positions and gear selections.

Albeit my bike is now way easier to wheelie because of the changes, and the 520 chain didn't help the matter, I can ride harder and run faster then most guys in stock trim because it's much easier to keep the motor in the power zone. I have lost approx 10% top speed because of the change. But in '02 the top speed was theoretical anyway because the bike didn't produce enough power to overcome drag. Now my girl screams to 155 with power the whole way.

Yea, you only wanna lower the front one....the only time you wanna change the rear one is when you race a lot and need specific gear ratios.....i dont know how to find out what the ratios are but it has something to do with power, geometry of the bike, and the gears using....there are some sheets in dealerships sometimes you can get to give you an idea on a average bike, but still will show you about how much ratio change you get.....used to race BMX....changing gear every race was normal on a national race level...every track was different and required different power...but i recomend that you try to get an idea of what the ratio change is if its what you want and wont generate too much power for you

uh yeah oooppps sorry for that i was thinking the wrong way one down in the front

Whether you chang ethe front or the rear doesn't matter. Simple rule of thumb, 1 tooth in the front is equal to 3 teeth in the back. Example, you could either drop the front 1 tooth or raise the rear 3 teeth and acomplish the same overall gearing advantage. The upside to changing the front as opposed to the rear, is a front sprocket is 16 bucks and a rear is 38. Also depending on how much you change the rear you may need a new chain with an extra link or two.
If you do make changes don't go with anything lowering in the front than a 15t. Anything smaller and run the risk of break chains. The sprocket becomes too tight of a radius for the chain to turn on and it stretches and breaks or hops the sprocket. Neither of which are good.

Thanks for the advice, I thought I should go down teeth on the front but was not sure how many. I raced Formula Fords in the US and Formula Renault in France and it seems that most race car engineering applies to bikes but I wanted to be sure.