Gearing?

[Smokin 440]

For XC what is the gearing combo I most likely want? Right now im running 20 inch tires on my 440ex with 37 teeth in the rear and 16 in the front I have plenty of power, but I'm wonderin if a little lower would be better or not.

[H_W]

I have a question, how can your 400 be bored .40 over and be a 440, when a 416 is bored .80 over? A .40 over bore is a 406.

[Smokin 440]

I was told .40 over was 440 obviously I was wrong but it is a 440

[H_W]

Ok, I was just wondering. And about the gearing, I have tried a 14 tooth sprocket on the front and I think my motor was just going through the gears to fast with it. I mean I might as well not even use 1st gear because it was too short. I have a 16 tooth also, for when I need top speed. I found that the stock 15 tooth was right for me. You may want to try gearing lower and see if you like it. It depends on what you like for your style of racing.

[jcs327]

To save the confusion about the bore. 440 does not mean that the bore is .040 over. 40 thousanths of an inch is the amount normally honed from the inside of the cylinder sleeve wall. a 440 means that the displacemant (area in the combustion chamber at top dead center) is 440 cubic centimeters. Most 440 engines are not actually 440cc though. some range from 435 to 438cc. Also, for a 440, the entire cylinder sleeve is replaced, not bored. In normal boring on stock cylinder sleves, the first bore is usually .040, and when the time comes for it to need it again, another .040 is shaved. the maximum safe bore for a normal cylinder sleeve is .080

[dbsbl1]

Originally posted by jcs327
a 440 means that the displacemant (area in the combustion chamber at top dead center) is 440 cubic centimeters.

The displacement is a volume, not an area, and I thought it was the difference in volume at bottom dead center and top dead center.

[jcs327]

you are correct, volume in cubic centimeters

[Bad Habit]

Originally posted by dbsbl1
The displacement is a volume, not an area, and I thought it was the difference in volume at bottom dead center and top dead center.

You're closer. What you described, is what calculates compression ratio. Displacement is the volume of the cylinder when measured from the top of the piston at Bottom Dead Center(BDC) to the top of the piston at Top Dead Center(TDC).

[quadrider400]

For what its worth;
I run 14 and 37 when i am in the mountain trails but I have 22" rears and need the lower gearing for the bigger rear tires.... when I go to the sand I change over to 15 and 37 but go to 20" rear Gekgo's with the mods listed below I have lots of power... before when I was stock I needed the 14 in the sand cause it was way off when it came to getting out of a steep bowl w/ no run at it....:cool:

[Chanman420q]

id put a 14 on, u should be okay, it wont be as bad because u have the 37, but for XC chances are ull never even make it into 4th gear so top speed isnt that big of a deal.