Here is some advice for those seeking the right sprocket combos for the KLX.

The standard ratio is 14/42 with a 106 link chain. You can run 13, 14, or 15 tooth front sprockets with this chain and rear combination, all give fairly tall gearing more suitable for the road and fast trails.

With a 108 link chain you can run a 46 tooth rear sprocket with the same three fronts as above. I feel this gives the best range of gearing. 13/46 is good for tight trails, 2nd gear being very good for hill climbs (at least on my modified KLX250 with a 300 kit). 15/46 can be used for higher speeds.

With a 110 link chain you can gear even lower, using a 50 tooth rear. This combo might be OK for unmodified 250, but with 13/50, first gear becomes almost redundant on a modified bike.

You can use a rear sprocket with any number of teeth in between, but then you will not be able to use one of the three 13, 14 or 15t front sprockets.
For example I tried a 47 rear, was able to run 13/47 &14/47 with a 108 link chain, but not the 15/47. The chain was too short.

The three magic numbers for chains of 106, 108 & 110 links are 56, 60 & 64. When you add the number of teeth on the front and rear sprocket, the corresponding chain will fit AND that of any combo + 1 or – 1.

My advice – go for a 108 link chain and a 46t rear. It gives the best spread of ratios.

 

Good stuff! Maybe you should add this to the 'new owners please read' sticky thread at the top of the page.

I have a question about the 15t front sprocket. Will it fit underneath the stock guard?

 

about that frontsprocketguard. has anyone just taken it off for good? is it really a guard to prevent damage or is it just another safety thing? i'd like to just toss itbut am afraid i might be missing what it's actual purpose is.

 

Some people take them off. Its more of a saftey issue as its a heck of a pinch point! Just be sure to put the chain guide back on if you do as thats important. Thats the curved steel piece under the cover.
db

 

right i forgot about that metal piece. i'm guessing that that's to protect the case if the chain breaks.

 

Yep, its supposed to but I have seen evidence where it does not work all the time. It also helps keep the chain on the front sprocket and possibly keep the mud and dirt out a little.
db

 

The guards are also required for state inspection in most states.
where did you find a 15t front???? PN # ?

 

Vaguely remember hearing that the 09 will have different gearing...Anyone know if this is true?

 

haven't heard gearing changes, just internal changes to the tranny regardingchanges formore positiveshifts and a different ratio in 6th or 5th. I'm on the verge of already ordering a 13-toother but I guess I should wait to see what comes stock as nothing is sure when a product changes.

 

alright fellas, so here I am riding trails with two KTM 400exc and they just seem to have ZERO wheel spin climbing hills....? then I came across this thread, whats the best sprocket for me, I dont need 70/80mph top end, but I do need to be able to climb hills and really dig in on the corners....just got some Pirelli MT's!