What is best gear ratio for WR250F???

[Duggaz]

I've recently purchased a 2003 WR250F, and have completed the Grey wire mod without really noticing any real difference, apart from slightly more top end snap. This may be because the gearing is totally inadequate. Its got a 13 tooth front sprocket with a 48 tooth rear sprocket. The gearing is understandably far too tall. I frequently ride technical, tight sections through forrest and the occasional moto-cross track.

On the really tight sections, I often find 1st too low and 2nd too high, similarly, sometimes 2nd is too low and 3rd too high. The bike's current top speed in a straight line is 155km/h (96 mph) , which is evidently too fast (not bad for supermotard though!!). Ideally (and if at all possible), I'd like the bike to be really "snappy" and pull wheelies in 1st, 2nd and 3rd without slipping the clutch, giving me good available power when needed.

Before I splash out on a new chain and sprockets I would like to make sure I'm on the right ratio for the terrain I ride.

Any advice would be greatly appreciated.

Many thanks,

Duggaz:thumbsup:

[Stripes123]

I would check the jetting and confirm it has the proper jets including a #40 leak jet. When I had my WR in offroad trim I think I was using a 52T rear sprocket

[gmoss357]

The stock 13/52 combo works best for the WR once it is opened up with exhaust and the mods. Anything more makes it top out too soon. I ran the stock combo for 3 years and once I put a different exhaust and opened it up, it worked great. You won't be disappointed with the combo.

[brutis1984]

The stock 13/52 combo works best for the WR once it is opened up with exhaust and the mods. Anything more makes it top out too soon. I ran the stock combo for 3 years and once I put a different exhaust and opened it up, it worked great. You won't be disappointed with the combo.

I am running the 13/52 (4.00 gearing I believe correct me if I am wrong) and I feel it is the right gearing for woods etc. but I seem to wear out the front sprocket pretty quick and there always seems to be a lot of noise from the chain/sprocket assembly. I am thinking the 13 is really a bit small for constant low end torquing. I would like to change to a 14 front with a comparable rear to keep the same gear ratio. Do you know what combo that would be? 14/50? Or possibly point me in the direction of a simplified formula to calculate final gear. I should be able to remember how to calculate gearing from all the physics I have had but sometimes I feel like I have forgotten more than I learned. I did look through my old physics books, I could not find an exact formula for this application it would have to be derived and I just do not have time. I am sure it exists out there I just can not find it.

[gpblue8]

I've played around quite a bit with the gearing on my 03. At the moment I have free mods plus a YZ pipe (get one if you can). I ride a lot of tight singletrack and hit the mx track every now and then. Stock is 13/52. 13/53 is a good combination to bring things just a bit closer without hurting your top end to much. I've got 12/51 now with only one ride. Seems to work fine with enough snap to pull the front end when needed. No matter what gearing you go with 1st will be low. Good luck!

[Dirt_Biker250]

I have my 2003 geared at 12/52. It works great for technical and the bike still has a way too fast top speed. I can pull wheelies in 1st, 2nd, and 3rd without slipping the clutch. I have done the gray wire cut and it made a HUGE difference along with JD Jetting and the boyesen accel pump cover and a FMF Titanium 4 pipe. I used to have 13/52 but decided that it made 2nd too slow and 3rd too fast. 12/52 makes the bike run great!

[av]

I am running the 13/52 (4.00 gearing I believe correct me if I am wrong) and I feel it is the right gearing for woods etc. but I seem to wear out the front sprocket pretty quick and there always seems to be a lot of noise from the chain/sprocket assembly. I am thinking the 13 is really a bit small for constant low end torquing. I would like to change to a 14 front with a comparable rear to keep the same gear ratio. Do you know what combo that would be? 14/50? Or possibly point me in the direction of a simplified formula to calculate final gear. I should be able to remember how to calculate gearing from all the physics I have had but sometimes I feel like I have forgotten more than I learned. I did look through my old physics books, I could not find an exact formula for this application it would have to be derived and I just do not have time. I am sure it exists out there I just can not find it.

Divide the rear count by the front count and you get the ratio -> 52/13 = 4.0

If you want the same 4.0 ratio using a 14T CS, then you'll need a 56T rear -> 56/14 = 4.0

[brutis1984]

Divide the rear count by the front count and you get the ratio -> 52/13 = 4.0

If you want the same 4.0 ratio using a 14T CS, then you'll need a 56T rear -> 56/14 = 4.0

Thanks man, I seem to always make things more complicated than they really are, that is kind of a no brainer. Thanks again.

[sndmn2]

The bike's current top speed in a straight line is 155km/h (96 mph)

Is that for real ? I can"t imagine that speed on your 250. My drz with a 14, 47 won"t even do that.

[gmoss357]

I am running the 13/52 (4.00 gearing I believe correct me if I am wrong) and I feel it is the right gearing for woods etc. but I seem to wear out the front sprocket pretty quick and there always seems to be a lot of noise from the chain/sprocket assembly. I am thinking the 13 is really a bit small for constant low end torquing. I would like to change to a 14 front with a comparable rear to keep the same gear ratio. Do you know what combo that would be? 14/50? Or possibly point me in the direction of a simplified formula to calculate final gear. I should be able to remember how to calculate gearing from all the physics I have had but sometimes I feel like I have forgotten more than I learned. I did look through my old physics books, I could not find an exact formula for this application it would have to be derived and I just do not have time. I am sure it exists out there I just can not find it.

I got 3 years out of my stock chain and sprockets. Probably should have changed them sooner, but they were still looking good. The rear showed very little wear when I took it off. Put new ones on just before I sold it.

[brutis1984]

I got 3 years out of my stock chain and sprockets. Probably should have changed them sooner, but they were still looking good. The rear showed very little wear when I took it off. Put new ones on just before I sold it.

The stock setup lasted me about 700mi. or 6mos. The rear looked fine and the chain was probably still within spec. but the front sprocket was extremely cupped and all the tips were leaning so I replaced all of it. In my opinion the front was toast, maybe it would have run another 700mi. or so but I couldn't take that chance while racing. I'm on the third setup know the previous lasted about the same amount of time as the stock, rear still looks good, chain is x-ring it should last a long time, but the front sprocket is already showing slight cupping in 300mi. or so. I am known for being very hard on equipment maybe it's just me.

[gmoss357]

combination of conditions and how hard you ride. I tried to always ride a gear high, which was usually 3rd. I never really worked the engine hard for extended periods of time either. I don't think the chain and sprockets on my new bike will last that long.

[Robert]

13/52 works best. 13/50 is good fortrail riding. When going for anything other than 13/52 the gap between 2nd & 3rd is too tall!!

[brutis1984]

combination of conditions and how hard you ride. I tried to always ride a gear high, which was usually 3rd. I never really worked the engine hard for extended periods of time either. I don't think the chain and sprockets on my new bike will last that long.

There is no way you can ride 3rd gear in most places we ride except in straights or open and very little of that, mostly bark wrangling. That may explain my sprocket wear, I am always hard on 1st and 2nd constant throttling.

[gmoss357]

There is no way you can ride 3rd gear in most places we ride except in straights or open and very little of that, mostly bark wrangling. That may explain my sprocket wear, I am always hard on 1st and 2nd constant throttling.

You'd be surprised. Our HS series loves to make the trails tight and twisty. As long as I was not climbing hills I rode 3rd, clutched, and braap when needed. Rode it like a mtn bike in the tight stuff, gassed it when I needed, to keep my momentum. I could come out of a turn very slow in 3rd, clutch, gas, and go. I ride the same way with my 300, just need to add one tooth to the rear to get it just right. Try it one time and let me know.

Garrett

[Dodger]

Is that for real ? I can"t imagine that speed on your 250. My drz with a 14, 47 won"t even do that.

I totally agree. My GF's '03 with stock gearing won't bearly touch 60. Hell, my '01 426 with 15/47 might top out around 80........

[SherpaHead]

When I got my 03 wr250f, it was at stock 13/52. Seemed way too low too me.

I use it in tight single track stuff primarily. Switched to 14/52, and now it feels

perfect.

96 mph ?!? I seriously doubt it. My Kawi 250 dualsports run 14/43 gearing and have

6 gears and they wont come close to that....

The only way a 250f would hit 96mph would be if you dropped it out of a helicopter....

[356]

96 mph ?!? I seriously doubt it. My Kawi 250 dualsports run 14/43 gearing and have

6 gears and they wont come close to that....

The only way a 250f would hit 96mph would be if you dropped it out of a helicopter....

Only way your going to hit 96mph is this.

http://i19.photobucket.com/albums/b189/yamaha356/wroffcliff.jpg

[Duggaz]

My speedo must be telling lies then. Last weekend I let it rip on a straight road and it read 155 km/h. It must need calibrating or something. Either way, the 13:48 is no good.

Thanks everyone for your sound advice. I haven't fully decided which ratio I'll go with yet but the factory 13:52 sounds good, and so does 12:51, although perhaps slightly too low.

The 12/52 sounds a bit too low geared.

Also, one of the gears should have an odd number of teeth and the other should have an even number of teeth to ensure even wear of the chain and sprockets.

So what do you reckon 13:52 or 12:51???

[Duggaz]

Only way your going to hit 96mph is this.

http://i19.photobucket.com/albums/b189/yamaha356/wroffcliff.jpg

You're actually wrong my friend...

If you remember physics at school, you would remember learning about kinematics, acceleration, velocity, gravity etc.

That cliff looks about 75m high, and using the laws of physics we know that:

distance (d) = 0.5*acceleration(a)*time(t) squared

(acceleration being gravity at 9.81 m/s/s)

therefore, after some transposition of formla, time (t) taken to hit the ground below =

t = square root of (2*75/9.81)

=3.91 seconds

calculating velocity (v) at impact,

v = a*t

v = 9.81*3.91

= 38.36 m/s

converting to mph (there are 1609.3 metres in a mile and 3600 seconds in an hour)...

38.36*(3600/1609.3)

= 85.8 mph

Evidently that is not 96 mph