Yeah I forgot you were running the 18" tires, definitely a 14 on the front....

 

yea, but isnt it if u put a bigger front sprocket u get MORE bottom end? i dont need that a already have too much wheelspin i am really confused

 

Putting a bigger sprocket on the front give you more top end.

 

You should go down to a 36t in the back and a 14t in the front. I had the same problem, after doing this I got killer acceleration. Note that you will lose top speed.

 

Crackhead... I am trying to say i have TOO MUCH acceleration and i have aboslutely no top speed, i dont need any more accel. Im trying to find a gearing combo to take some hp from the bottom and get it to the top!! Im planning to do motocross in the future and everytime i start off the line just sitting there spinning and spinning, And i have a friend with a stock 300ex and he is the littlest bit slower than me. I think its kinda bad that a 300ex can keep up with me. So ill ask again... what sprocket ratio should i use with 18in. tires to get some more top end. RIght now i have 13f 39r. My quad is sitting in the garage waiting to for me to put some new sprockets on. Thanks

 

I have 18" shredders, 14t:36T sprockets, and i still hit atleast 70. I raced a 300ex, I could push my bike faster than that bike goes. How can you only be doing 40? The smaller sprocket you get the more accel you get, the bigger sprocket you get in the rear, you get top speed but you lose accel, are you using all your gears? I dont see how you can only be doing 40 with a 39.

 

Crackhead you got it backwards, larger front and or smaller rear will give you top speed.

3rd eye if your buying sprockets find out what the other guys you race with use, I don't know the size of your track so it's hard to pick the right setup. You will need at least a 14 in the front and smaller in the back than the 39 you now have....

 

othirdeyeo3, Powerslider is right. Crackhead no offense, but you are mistaken. I have run 15/38 and 15/36 on my old 440EX and the difference in speed was very noticeable. A friend of mine that I race with ran 16/36 so technically his bike would be faster, but his 440 was not powerful enough to rev out that gearing so my Sparks 440EX would outrun him on straightaways. Crackhead, possibly the reason you think your R is slower is because it is not powerful enough to rev out with that tall gearing.

With 18" tires you want to gear it somewhere in the neighborhood of 13/39. Or maybe even 14/39 like powerslider said. Obviously, finding out what others are running at your local track would help you out, but at least you would be in the ballpark at 14/39.