2003 yz450 gearing for pure Moto conditions

I am thinking about changing to a 47 tooth rear sprocket for larger outdoor tracks with a few tight corners. Has anyone done testing of gearing set-ups for various track conditions? I heard that gearing-up helps with reducing rider fatigue and improving cornering for most outdoor tracks. I am concerned about stalling the bike or loosing time in the tight corners. I am an intermediate weighing in at 185lbs and I have increased the fly wheel weight by 4 oz. Your inputs would be appreciated.


PowerNow works really well in both the 450F and 250F

The Jardine RT4 exhaust system on the 450F is awesome. Better than FMF in my opinion. I bought both and sold the FMF.

I also own an 03 250F. The improvement on mid and top from the Big Gun on the 250F are incredible. The bike screams on top like my old ported/polished YZ125's. I tried Dr D's and Yosh first but preferred Big Gun Race exhaust system.

I run a 6oz on mine. The 4 didnt really make much difference. It helped a little with stalling but not enough. Get the 6 and pull your TPS. It works great.

At glen Helen, I run a 48 in the rear. Works just fine.

14/50, do it to it.

Was pretty good when i had mine.

I tried the 47 rear and liked it. I would ride around using 2nd and 3rd gear on most tracks. The only problem was with starts. It made 2nd just a little to tall for my taste. I couldn't launch the bike cleanly and then it was akward deciding whether or not to grab third based on the length of most of the start straights. I changed to a 50 rear and now use 3rd and 4th on the track. I still launch in second and then grab 3rd about 20ft out of the gate. I also added a holeshot device to my forks. This combo seemed to work pretty good for me in a strictly moto environment. :)

I had the 47 tooth rear with a GYT-R exhaust and 4 oz flywheel weight from Dr. D. Smoothed out the power well, and did not sacrifice low end at all. Our track is very tight in some sections, big table tops or doubles in the exits, and I never really had a problem with the gearing. I was holeshot king in 2nd gear, no problems. Between 2nd and 3rd is a big gap, so I tended to ride in this zone. Between 3rd and 4th was really wide and I only used 4th to smoothe big landings, or on really long stretches.

Yup. After switching around some, I'm using 14/47 for all tracks that are not directly "tight". Second is actually usable in corners, lets you have some room to accelerate on the exit and keeps you way safe from stalls. 3rd is still the main gear for most of the track and becomes a tad longer with super good drive. With 14/48 I almost never use 2nd and am often tempted to crawl around hairpins in 3rd and get caught with a stall when grabbing a handful on the exit. Three kicks later everybody who was chasing is long gone. I have a pretty big 11oz. flywheel, and with the 14/47 it makes for a very predictable but powerful thrust with lots of traction. Will shortly be installing the '04 (-18-00) accellerator pump diaphragm with shorter squirt duration and a Power Now for hopefully even better from-idle snap and even more reduce the chance of stalls.


Ride safe.

To add to my previous post, I'm running a GYT flywheel and the FMF Ti Muffler (14in). I wasn't looking to smooth the power with my gearing changes, I was looking for the right combo based on gear ratio numbers and sprocket size. With the 14/50 sprockets I found what I needed. The combo of the slightly heavier flywheel and FMF can changed my power such that the motor doesn't quite come on as hard down low but seems to rev out a little more freely. :)

The guys at Yamaha of troy were using the 47 so I tried it and loves it. Although check this out

14 15

47 3.357 3.133

48 3.429 3.200

49 3.500 3.267

50 3.571 3.333

51 3.643 3.400

52 3.714 3.467

I might go 15 51 to get the sprockets to last longer.

the ratio is almost the same.

So if you go to 15 front does the stock chain guard still work ?

Yeah, a 15 will fit with the stock chain guard. You may have to remove it to put on the sprocket and chain and put it back on last. It's snug but it clears. :)

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