2000 SXr600 gear question

[ridesrx]

I want to change the gearing in my 600 SXr. It's stock except 51-43 helix, green sec. spring and 8ab weights. It has the stock 20/39 gears in it. Should I go to a 19 tooth or 18 tooth? Can I use the same chain with an 18 tooth?

Also if anyone has any good gears, I'm lookin to buy one.
Thanks, Chad.

 

[ekimsx600]

I have the same set up as you, but I installed 8 tooth drivers which I've heard is like dropping 2 1/2 teeth. It feels like a new sled with this combo. It lauches hard and comes out out the corners like crazy.