I'm in need of a 15 tooth sprocket. Hasanyone had used this combo with the stock 42 tooth sprocket? I think i need to lower my r's because when i'm doing 75 on the highway i'm at 8,000 rpm. I would never let my truck spin out that much. Plus i think it would help with my trail grunt.

 

15t will ruin your trail grunt. Think of starting out on a mountain bike in a high gear. These bikes aren't really made to run 75mph for extended periods. Get a 351 kit The extra power, along with a 15t might give you just what your looking for.
Dan

 

I 2nd that.

 

I have one you can have if you want it. Previous owner put it on. I'm putting on my 13t tomorrow. It goes good on highway but too high for my taste in town or on trails. Let me know.

 

I have tried 15/42 on my bike, but that is as a modified 300. I doubt a standard 250 would pull this gear, and as said, would be useless in the trails.

I now have two sets of wheels, one with road tyres, the other knobbies. Each with discs and sprockets. The rear road has a 46T and the knobbie a 47T

I change the front sprockets betweeen 13, 14 and 15 depending where I am riding.

 

Do you some have sort of quick release set-up on that sprocket nut? How long does a pre-ride switch take? (wheels and sprocket switch)

 

Thanks SM, let me know if 1Broncoman can't use it.
I just got a few heat cycles on it because it's so damn cold right now, but i like the increased torque and think the 15 tooth will be the ticket.

 

The 250 can easily pull the 15. And a 16 and a 17, if they would fit. I'm running the equivalent of over 17 teeth on the front, so you might enjoy the following data.

I know I'm going to be the odd man out here, but you know how compromises go. If we use the 13 to "optimize" the low speed gearing, the bike is screaming on the freeway. If we "optimize" the 6th gear for the freeway, the bike is not nearly as useful at low speed on the trail.

So I get that. But right now I'm not able to commute daily to work on my 650, and the 250 has been pressed into service. First, I fit a 15 on the front (kept the stock 42 rear). Nice improvement. Not knowing of any rear sprocket choices that were smaller, the next thing I did was buy a Pirelli MT43 for the rear. That baby is 81.4" in circumference, compared to the stock tire at 76.5". That's the equivalent to keeping the stock rear tire and somehow fitting a 16 tooth front. Loved it more.

I kept poking around. Sure enough, there is a FACTORY STEEL sprocket for this bike with 39 teeth! (P/N 42041-1507)... it's used on the supermoto version of this bike. So I ordered it from my dealer and put it on. Now I'm at the equivalaent of 17.2 teeth on the front with a stock rear tire. And I really like it for commuting. At 6000 rpm, the bike is going 73 mph indicated (66 actual).

So I realize it's a compromise we all have to make, but YES the bike will pull a 15 on the street easily. We did Moab for a week last May, and I ran 15/42 and the stock rear tire for the entire trip and loved it.

Anyway, there's data for what it's worth.

 

SM, i received the sprocket today in the mail, thank you and if you get out this way, i owe you a few beers!!!!
I'll see if i can give it a go when the snow melts.
Aloha,
Gary

 

Hey Gary!
I know this post is a little old by now, but I'm looking for some guidance on the 15t sprocket. I have a 2012 KLX 250s and I just ordered a 15t sprocket for the front, but after pulling off the guard to look at the sprocket it doesnt look like anything bigger than 14 will fit? I just curious to see if it will fit before it shows up.. thanks
-James