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I have spent a lot of time testing on each 2021 machine you see below. I went back and forth on several bikes to see which gearing would be good for the average rider. I did my evaluations on tight clay based tracks to flowing sandier based type desert courses. Since the word “gearing” is still in the subject line in a lot of my emails, I thought I would condense some of the best gearing specs I have come up with for the 2021 MX test machines so far. A couple of these gearing specs have evolved since 2020 so don’t expect some of these to be the same from last year. I DO NOT however just change the gearing for the sake of changing the gearing, like some other media testing outlets. However, if a certain bike does need an engine character change or maybe the transmission spacing needs help, we will try different gearing. These gearing specs are for stock engines or with aftermarket mufflers. If you have engine work done to your bike, chances are you could change gearing on a few of these machines. I also attached a couple links to some ECU maps (to a few bikes) that I preferred, to compliment the recommended gearing specs. As usual if you have any questions I am here to help you. Email firstname.lastname@example.org and I will be happy to assist you.
YZ250F: Stock 13/50 Recommended 13/50 ECU: (Keefer Free Feeling Map)
YZ450F: Stock 13/49 Recommended 13/49 or 14/53 ECU: (TP 3.0 or 5.0) The 14/53 gearing will help the chassis settle more on acceleration as well as help calm the bike on de-cel. This also keeps third gear usable in almost all track conditions.
KX250: Stock/Recommended 13/50 ECU: (Keefer Map) You can view the KX 250 map here: https://www.keeferinctesting.com/motocross-testing/2020/1/6/2020-kawasaki-kx250-top-5-mods
KX450: Stock 13/50 Recommended 13/51 ECU: (Keefer Map) You can view the KX450 map here: https://www.keeferinctesting.com/motocross-testing/2019/8/25/2020-kawasaki-kx450-reviewbaseline-settings.
Going to a 13/51, instead of the stock 13/50 gearing, helps the rider get into third gear quicker coming out of corners. The stock 13/50 will not pull third gear in corners without using a lot of clutch.
2020 RM-Z250: Stock/Recommended 13/50 White coupler (Stock)
2020 RM-Z450: Stock 13/50 Recommended 13/51 White coupler (Helps pulling power down low on deep tracks)
CRF250R: Stock 13/48 Recommended: 13/49 (Helps rider get into third gear earlier and gives more pulling power without sacrificing second gear roll on). The stock 13/48 makes second and third gear feel super short/close together, but the 13/49 will allow you to just run third gear in corners.)
CRF450R: Stock 13/49 Recommended: 13/49 Unlike last year’s Honda CRF450R, the new hydraulic clutch is a tight fit for a 14T countershaft and I just don’t trust it because it is too damn close to the slave cylinder.
This set up on all three bikes will help settle the rear end out of corners/square edge/braking bumps. It will also help 2nd-3rd gear recovery as well as transition between each gear.
250 SX-F: Stock 14/51 Recommended 14/52
350 SX-F: Stock 14/51 Recommended 14/53
450 SX-F: Stock 13/49 Recommended 14/52
This set up on all three bikes will help settle the rear end out of corners and help with 2nd-3rd gear transition exiting corners.
FC 250: Stock 14/51 Recommended 14/52
FC350: Stock 14/51 Recommended 14/52
FC450: Stock 13/49 Recommended 14/52
This set up on both bikes will help settle the rear end out of corners and help with 2nd-3rd gear transition exiting corners.
MC 250: Stock 14/51 Recommended 14/52
MC 450: Stock 13/49 Recommended 14/52