I understand that a 13T sprocket will give the bike more throttle response and low end torque but does the bike lose much top end by switching to a 13T? If I am using the bike for commuting, would I be able to hold "a speedometer indicated" 65 mph with a 13T sprocket?

 

I would also like to know. I plan on putting a DID chain on my bike and may as well drop a tooth since I'm pulling the chain.

 

If you have it opened up (intake and exhaust), yea.
If not, I doubt it.

When I had the Big Gun System on I think I got up to ~68 with a little more left to go.

I am selling the Big Gun System, any one interested?
It is like new, just to loud for this old Guy

See setup below I gte up to 65mpg with winding it too hard.
Hope that helps.

But I digress.

 

correction:

See setup below I gte up to 65mpg withOUT winding it too hard.

 

pm me bout that big gun system there slapdrum i may be interested

and i think you ment mph not mpg lol but we all know what you mean haha

 

Just going down to a 13 on the front and leaving the stock rear alone, you will be fine. I did 700 miles on mine with the 13-45 and at 7,000 I can cruise at 60 indicated (56.4 mph) Slow down and enjoy the scenery.

 

Didn't the 6th gear ratio change on the 2009 so it doesn't have the same "overdrive" of the 2006/2007 models? Like Deej, I changed to the 13T on my 2007 and not only did I get better low end, I also got a very useable 6th gear for off-trail crusing. That may not be the case on your 2009.

 

To me you loose 1 tooth out of 14, so 1/14=7% you just add 7% to your current rpm count at 65mph!
For the same rpm you should go 7% slower, from 65mph to 60.5 mph
So If you can run at 70mph with your 14 teeth you will be able to get to 65mpg with a 13th.

 

My 09 holds an indicated 75 pretty easily with the 13 tooth and stock rear sprocket. I have all the usual uncorking mods.

 

My two cents
2007 KLX 250 NO mods as yet, Using synthetic oil
100mph!
I think it's cause I broke it in w/the "MOTOTUNEUSA" method

http://www.mototuneusa.com/break_in_secrets.htm

I've Got one of BBlue's TM33/34 still in the box. Waiting for my wife to go on vacation. Then the bike can sit in the living room of the apartment while I work on the carb hand guards and a skid plate.

I doubt she'll go much faster but hope it'll get there quicker and with out the 45/50 degree air temp needed for the stock carb to get me (200lbs) to 100mph.
Best o' luck Marc