KDX200 1990SR - Sprocket Ratio 14/43

Discussion specific to KDX models not sold in the USA
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rickvs355
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Joined: 08:09 pm Mar 23 2022
Country: Australia

KDX200 1990SR - Sprocket Ratio 14/43

Post by rickvs355 »

Hi guys

I know that this topic has been flogged to death but I have a specific question that maybe someone can help with.
The stock E model gearing is 13/47.
The stock F (SR) model in Australia is 14/45. (Noted that this is with a 28mm carb, restricted expansion chamber, restricted air box and possibly different ignition timing)
My 1990 SR has full DG exhaust, boeysen reeds (rad block), Lectron 36mm carb, E model airbox modified, BP8ES plug.
I will be doing 50:50 Road (including highway) and trail (some hilly stuff)
I am leaning towards 14/43 which is just a couple of rear teeth taller than stock. Do you reckon this seems a feasable option??
Has anyone in the US gone this tall before?

I purchased the bike with 12/50 and it pulled pretty hard down low but didn't really get it to 6th gear yet.
First thing I did was strip it down and a full restoration so didn't test much - Pic attached

cheers
Rick
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bufftester
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Re: KDX200 1990SR - Sprocket Ratio 14/43

Post by bufftester »

The stock gearing at 14/45 will probably be sufficient for your 50/50 riding. 14/43 will give you a little more top end speed, but you will lose a bit of grunt on the bottom. 12/50?? I don't know of anyone running that low on a 200/220, unless you're going to chase mountain goats. I'm in the Pacific NW, lots of mountains and technical, and run 13/47 on my 220 which is good for about 60 MPH but will climb nearly anything. Check out Gearing Commander and you can play around with the numbers
rickvs355
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Country: Australia

Re: KDX200 1990SR - Sprocket Ratio 14/43

Post by rickvs355 »

Thanks for that. Great link. 43 sprocket does 100km/h at 5800 rpm and the 45 does it at 6000rpm. Might try the 43 just a touch taller but not a lot if difference. Hoping with the extra hp that i have over stock it should pull ok with the 43. Speed limit is mostly 100km/h here, not planning on going much quicker on the road. Will be riding against wr426 so extra legs wont hurt im thinking
rickvs355
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Joined: 08:09 pm Mar 23 2022
Country: Australia

Re: KDX200 1990SR - Sprocket Ratio 14/43

Post by rickvs355 »

Just a follow up. 14/43 is nice on the road and in the open flat tracks. Second is a big drifter with this ratio and it pulls off the line in first fine.
I have however now changed to 13/43 as I found out that the wr426 that i am riding with has a 14/50 so is pretty low itself ánd only cruises at 90kph so I dont need the legs to compete. Will update once I have riden 13/43
Pawlos312
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Re: KDX200 1990SR - Sprocket Ratio 14/43

Post by Pawlos312 »

By the way, notice that the SR version has completely different gear ratios - first gear is shorter, and all other gears ratios are longer than the E version.
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