Hey i have a 400ex with a fmf powercore 4 and a k&n airfilter with jets. I was wundering what the best sprocket combination would be to race on a track against other 400's. My rear tires are 18 inches and the front are stock. I am currently running a 16 front and a 36 rear. I have a 15 and 16 front to choose from and a 38 and 36. Out of the sprockets i have, i was wundering which combination would be the best for coming out of corners and jumping but still have a decent top speed.

Thanks.

 

i would go with a 13 or 14 tooth. 13 will allow more low end but makes the the top end slower. 14 is stock and pretty much in between. It gives you a little of both low end and top end

 

my ex is a 2004 so the combo is a 15/38 stock. im running a 16/36. thats what it came with. but out of the sprockets i have, what would the best combo be for a track/trail.

 

That's a tough one to answer because it depends so much on th track. If it's tight, 13 front, 38 rear. If it has a lot of straights and open, 16F 36R. And then there's everything in between. I think run what you brung and see what happens. Take the others with you and change if needed.

 

good idea man, im thinking about running a 15/36 because, i have the 18 inch rear tires. a 400ex with a 14/38 ratio runs around 64mph with 20 inch tires. if i do a 15/36 ratio, it will run around 65, which is very close. what you think?

 

and almost all tracks you go on, there are some sharp corners.

 

I used to go through this when I raced go karts. Some tracks were long & narrow and some were short and fat. Some were long and fat. Lap time is what you have to look at. If you choose a combo that makes you fast at top end, you will be slower accelerating. So, you may pass a guy at the end of the straight, but he'll pass you coming out of the ture. If you choose a combo that gives you quick acceleration, you will be slow top end and may get passed on the straight. There's no combo that will make you fast accelerating AND fast top end. You have to give up one for the other, ALWAYS. So, you choose a combo that gives you the best lap time total. Everything is a trade off. You just have to find the best trade that will make the fastest total lap time.

Now, if you REALLY want to find the perfect combo, you have to dyno your quad. You are looking for the torque band. Once you find the RPM range for your torque band, you then can gear it so that your quad stays in that band no matter where you are on the track. You'll need a tach on it so you can watch it. They also make tachs that record highest and lowest RPM. Let's say the torque band is from 3000 RPM to 6500 RPM. Below and above those RPM's, the torque falls off. So, you choose sprockets for each track you race on that will keep your motor in that RPM range. Never below 3000 or above 6500. Very hard to do, but this is one thing that will make your bike as fast as it can be. Maybe not fast enough to win, but as fast as it can be. Then of course, you have to set the suspension which is a whole nuther ball game. Get the tires right, air pressure, then you have to be the best rider. Sheesh. No wonder I just ride trails anymore.

 

thanks man for ure input, its really gona help !