well lately i have been doing a lot of freeway riding back and forth from long beach, about 85 miles each way. ive been using the 14 tooth, which is fine, just tuck behind slow traffic and cruise, about 70mph near 8K, so keep it 65mph at 7,500 rpm or so. with traffic flying past at times, it gets old having your head on a swivel at all times in case some one comes fly up from behind (edit: drive 91/15 freeways for examples). a lot of people say the stock 250 cant pull a 15 tooth cs, and thats 351s area, i call bs.
i just got my jt 15 tooth cs yesterday and threw it on for a test ride. now i can cruise a honest 70 mph at ~7,400 rpm, and it didnt greatly effect how the bike accelerated. i can now cruise with the flow of traffic from the most part. now keep in mind im 145lbs, so if your 200+, this might not work for you. also keep in mind, this is with almost a perfect match to the stock tires, so any 606 or tall tire like it will drop the rpm even more.

cliff notes:

14cs------------15cs
8k @ 70mph-----7,4K @ 70mph
66mpg freeway--well have to see, but its going to be more

 

i'm at roughly 76 rpm at 80 mph with the 15t front and stock rear...before with the stock 14t, i was at about 81 rpm at 80 mph...wonder why it's so different...

 

Do you have an SF?

 

yes...an sf...

 

i havent heard Anybody say it cant pull a 15..

 

I ran the 15/39 on my klx and I could take some really steep hill climbs. I've been riding over 20yrs on motocross bikes. Just rev the crap out of it and go haha. I am now runnin my factory gearing now since I have the motor broken in now. Havnt taken it hillclimbin yet since the swap. Of course im 5'11 and 144.

 

Wow 15 tooth, I bet 6th gear feels like neutral on an incline.

 

I think the 15 would be OK for an SF on the pavement. You'll lose lots of snap...something of which the KLX doesn't have a lot of. The guy I bought my S model from had a 15 on the bike with a full Muzzy exhaust, all airbox mods, and a DJ kit. It tooled around on the pavement alright, but the minute I took it off road, the bike was a paperweight. That was with the S model gearing of 15/42 and a rather small more pavement oriented DS tire. If I were not doing anything rougher than dirt roads along with my pavement, I think it will pull a 15 in very mediocre fashion. Pulling a hill with any wind is going to require a downshift, more than likely.

 

doing almost all freeway commutes...i don't have any problems cruising at 80 mph and keeping up with traffic....easily pulls up to 90 mph if needed with full throttle...haven't blasted up any steep mountains at this speed, but haven't had any problems going up steep san francisco and peninsula hills with the 15t front....

all i have is exhaust, jet kit and k&n filter....

 

Just out of curiosity, where do you guys order your sprockets from?