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XR400R sprocket ratios


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I have a mates Honda XR400R here, it's around a 2000 model. It is currently fitted with a 15 / 40 sprocket setup (which the standard Australian setup in contrast to the USA which I believe had 15 / 45) but he is complaining that the gears are too long for off roading - the bike is not street registered and no present plans to ride on the road.

 

He has ridden my XR250R which has the 280cc piston, carby, exhaust etc. done and is fitted with a 13 / 46 setup. I chose this as the factory off road gearing was 13 / 46 for the XR250's. The owner liked this ratio, but I'm not sure if it's maybe a bit too low for the XR400 considering the extra cc's it has?

 

Can anyone advise what the factory off roading gearing was for the XR400?

And when purchasing a new chain, is there a method to calculate how many links are usually required?

 

I was thinking a 14 / 45 setup perhaps?

Edited by twr7cx
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15/45 is stock here in the states. That will make a dramatic improvement off road. No need to go much lower unless your on really tight trails where you need 1st gear for long stretches of trail.

 

The 250 has different internal gearing and a 6 speed trans so final reduction is quite different on the 2 bikes. 13/46 on a 400 would be tractor like low gearing.

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I agree, going with 15/45 would be a much better. If you do a lot of hill climbing and slow technical stuff, the 14/45 would be the way to go. Much lower than that and he'll be at the opposite end of the spectrum from the problem he's having now. You run out of gear too quickly before needing to shift again and you find you're shifting more than you want to be.

Where as, what he has now is causing him to have to feather the clutch a lot. I liked the 14/45 because it was low enough for technical work, yet high enough if I needed to ride the road between trailheads. And I didn't need to feather the clutch much, just throttle control in the technical stuff.

Not a good idea to go smaller than a 14 on the front of an XR400.

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The stock gearing in europe is 15/45.

 

I use the stock 15/45 gearing now, since I sold the trailer. It is OK offroad and acceptable on the blacktop up to about 100km/h.

 

I had 14/45 when I had the trailer and did not ride the bike as much on the blacktop..

 

I did try 15/40 and did not like it offroad. 15/45 is high enough gearing for the blacktop anyway, the XR4 is a dirtbike after all, 90-100 km/h is enough.

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A tooth here & there can make a big difference, I have one 416 bore + pipe with 15/40 gearing & another 440 BIG cam BIG carby + pipe with 15/45 gearing. I'm actually thinking of going 15/42 with both of them & getting a 14 & 16 tooth front to swap in when the ride required it.

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i been running 13/45 on mine for three years or about 2500 miles, no issues. i ride a lot of tight trails, will be doing a desert ride at the end of tbe month and will go to 14/45 for that. 15/45 is just to tall for most trail ridding i do.

with 13/45 i can cruise the single trac in 2 and third and go into 1 st for tough stuff, in 2nd i can climb any hill without a lot of clutch work and its forgiving. On the road it can still cruise at 50-55 with out a lot of stress still run up to 70+ if you have to. with the 14/45 you can do 60 fine and run up to 80mph in a pinch. i would think a 15/45 would get you to 90 + flat out.

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From the OP's setup at 15/40, here are all the other combinations mentioned in this thread. 

 

they are sorted by the lowest ratio to the highest. 

 

The 4th column compares the difference to the OP's 15/40 and the last column shows the difference from one ration to the next one up.

 

10% can make quite a bit of difference.  Pick a ratio you want to try, and make that with whatever rear and a 15 tooth front.  Then you can change the cheap, easily changed front down to 14 or up to 16 to fine tune your the ratio you like.

 

               Front     Rear      Ratio        Difference from 15/40      Difference from previous

OP setup    15       40          2.67      

                   16       42         2.63           -1.59%                                    -1.59%  

                   15       42         2.80            4.76%                                     6.25%  

                   15       45         3.00           11.11%                                     6.67%  

                   14       42         3.00           11.11%                                     0.00%  

                   13       40         3.08           13.33%                                     2.50%  

                   14       45         3.21           17.04%                                     4.27%  

                   14       48         3.43           22.22%                                     6.25%  

                   13       45         3.46           22.96%                                     0.95%  

                   13       46         3.54           24.64%                                     2.17%

Edited by scott_01_xr400
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I run 13/48, but my trails leave me wanting to go even lower sometimes. My top speed is around 50 wide open if I can actually find a stretch where I can open'er up. The 13t front sprocket has a significantly shorter life span than the stocker, due to the smaller contact patch. (More stress on fewer teeth at a time.) The chain noise is a bit disconcerting also; I can tell the exact point at which the oil slings off and the chain is dry. But besides that, no mechanical issues for many hard single track miles, even with the cheesy circlip holding it on. :D

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