You're welcome.
Also look up threads for removing that bastid of a counter shaft nut. Unless you've already busted that thing loose, prepare to obtain the appropriate socket, breaker bar, and likely a cheater bar to go along with. I like to use a strong rod through the sprocket against the swing arm to chock the rear wheel.

 

Top speed and acceleration definitely improved with a 13t front sprocket.
You'll have to start off downhill with a 16t! And god forbid you should run into a fly. The bike would be stopped dead in its tracks.
PS Love my 2009. 13:42. Much more efficient and better for the engine.

 

I'm going to try the 15T/39T combo and see how it goes

 

I put a 15 tooth front sprocket on my 06 klx, but it's a 351 big bore, a stock 250 cc klx is really going to struggle to maintain speed in 6th gear if you get any sort of headwind or going uphill.

 

Hi - which Big Bore Kit would you recommend I install?. I'm going to run a 15T/39T sprocket combo with or without a Big Bore Kit.

 

Cheapest is the AHL 299cc kit at around $180 unless on sale, on Amazon. Then there are the 331cc kits from B&B and Athena, and the B&B 351cc kits at around $550. With the 15/39 you just downshift if needed and usually are in 5th at any speed under around 55 mph depending on conditions. If I rode mostly street I'd do the 15/39 and just use the top gear when over 60 mph and shift as needed. Not much good if doing much serious dual sport. Then the stock is better unless a lot of single track, then run a 14/47 or so.

 

Ok - first I will go with the 15T/39T combo - with this combo do you think I could get 140kph? I had a 2016 Honda CRF250 road tires and 123kph max - hoping for more with the Kawasaki, what do you think?

 

Maybe I'm missing something. You got super moto wheels on it?
BTW I can get that with 13:42.

 

No - 21 and 18 wheels and Pirelli Scorpion tires

 

Yes, you probably can do that, but not with a headwind or with a grade. I found I could run around 70 mph fairly regularly on relatively flat ground riding normal.. It is going to be more about pushing wind, the power is just not there to push the wind resistance at that level. Realize air is a fluid and you are pushing an object through the fluid, a very un-aerodynamic object through that fluid. In air the rate of drag quadruples as speed doubles. If you had to push 50 kg/m at 50 kph you would have to push 200 kg/m at 100 kph. Unfortunately there's only so much power in that little engine. Your sitting up in the wind probably will knock off nearly 10 kph at top speed. We found an aerodynamic crouch on our Honda MB5s would add around 3 kph at their top speed. Laying out on them would do maybe another 1 or so. Air resistance is a nasty thing... unless you're trying to stop.