'meaningless' meaning that just going up 3 in the rear and buying a new chain is ignorant when you can acquire the same thing by spending $10 on a 13-tooth up front and keeping the oem chain and sprocket which is what makes up the brunt of expense when re-gearing. if you just keep the oem 14 and jump up to 45 in the rear, it's the same as keeping the oem 42 and jumping down one to 13 up front. the reason i eventually went 45 in the rear was to get even more low end. but a good chain only runs $60 and a sprocket from $30 to $60. don't know where you're getting the $300 from. granted going to 45 in the rear along with my 13 did add a little more low end compared to just the 13 up front and oem 42 in back, it didn't add near as much noticeable low end asthe jump from 13 up front and oem 42 in back. notice that i did write that it was just my opinion. the most effective and economical mod for the KLX 250S is adding a 13-tooth countershaft sprocket. it's an obvious improvement that's barely over $10, and it is not noisy. it will wake up a totally stock bike and make it more rideable and even a little wheelieable from the standpoint of not having a pipe or any intake or carb mods.

 

looks like duane answered the question first. basically, if you want to spend more money, go for the 45 and new chain. it is significantly more expensive (probably $120 more) than just spending $10-$15 on a new front sprocket. the front sprocket is tons easier to change out than a rear also. changing the rear requires removing the rear wheel, the front just requires loosening up the chain. then it's just removing the nut that holds the front sprocket on along with the lock-washer. there's several threads that talk about this removal, do a search. trust me on all this, i speak from experience. of course, jmo.