Hello all,
I have been lurking here for quite awhile. The information gained here helped me make the descion to jump in to the dual sport bike world. I picked up a 09 klx with 311 miles about four months ago! I since have put on 750 miles. Almost all off road. Just got my uhd tubes, slime and rim locks in the mail last week. Hoping Xmas brings a rack, hand guards and a skid plate.
The riding out my door is relatively steep and rocky so I have been thinking about changing to a 13 front. My only worry is how much top end I will lose. I also have been riding fast fire roads and plan on some longer touring rides. I'm not a serious speedster but the top end isnt all that, so wondering how much I will lose? Also is it an easy job to change and do I need to do anything to the chain?
Thanks in advance and will post some pics and ride stories as they come!

 

Welcome to the forums, and the best bike ever! You'll lose a little top end speed, but you will still be able to do 60 easily, I did the 13 tooth 6 years ago when I first got the bike, then I changed out the rear to a 45 from the 42. I can still do 60. But the low end power is well worth it.

 

Theoretical top end goes from 108 to about 100 although you’ll never hit red-line in sixth gear.
A better measurement might be at 60 mph. You’ll go from 5750 rpm stock to 6200 rpm after the swap.


Download this if you want more granular detail and / or want to experiment.

 

No top end loss whatsoever as the bike doesn't have the power to pull redline in top gear, not even close.

 

My experience is that you'll actually pick up a little top speed (~5-10km/h) in 6th because you won't be downshifting as much to maintain speed up hills or into headwinds.

You'll need to be prepared for the sprocket nut to be VERY tight. Some folks use an impact wrench to remove it but that idea makes me a little nervous about damage to the gearbox. Others have used a torch but that also scares me a bit due to the possibility of melting the C/S seal. I used a 3' breaker bar and a LOT of muscle!

 

The 13T was one of the best things I did to my KLX, and that's after I had alreday installed a 47 rear sprocket. This opened up my gear selection for off road situations in a massively pleasant way. Your described off road conditions just about require the 13T or a rear sprocket to achieve the same thing. If you really off road in any rough conditions where you have to get off and on the gas frequently, you have to gear this sucker down.

 

13 tooth on my 2012. Not missing anything on the top end.

 

Awesome, Thanks everyone. I'm going to get this going asap!

 

TNC, do you find the 13/47 gearing is low enough for single track and double track riding? I'm running 13/42, now. I don't want to ride my KLX on road anymore than I have to, so being too slow shouldn't be an issue. About all I want to do is ride double track, some single track, some dirt roads, and whatever I can find in the winter, now that I've studded my tires.

 

I'll chime in before TNC gets a chance to .

I ran 13/49 (and 15/49) before doing the 351 kit. With the 351, I dropped to 45 rear and run 13/45 or 15/45. I change the front sprocket several times during the year depending on riding conditions. My current rear tire is pretty small diameter compared to what most run and what will go on next, which is probably equivalent to a tooth or two on the rear.

After some more serious riding this last summer, I'm really tempted to put the 49 back on, especially with the larger tire that will be going on soon.

45 requires a couple fewer chain links than the 49. (108 v 110 IIRC)

For me, the 13/49 makes sense. And I can see 13/47 working very nicely. On the 2006/07 bikes, you can keep the chain guard up to 48 rear (from what others have said). I had to remove it with the 49 and haven't bothered to reinstall.