I can't say definitively, but I'm pretty sure that the chain rides on the chain guide wear blocks with stock gearing. I put an aftermarket (Moose Racing) rear chain guide on mine, and you can buy replacement 'wear blocks'. Because they're replaceable and called 'wear blocks', I would say it's safe to assume that even the stock setup has the chain riding on these wear blocks.

 

And to add to rgmr....

I used the stock unit with a 49 rear with success than damaged the chain guide in the rocks. It was replaced with a hotfootmoto unit which worked okay with the 49 (and smaller) but 51 is too large and I had to move the chain guide back with a homemade bracket.

 

I just did the 13T/45T swap with a 108 link chain on my 2007 KLX250s and while I haven't been able to ride it much yet, I was able to get the front tire in the air easier, and you can feel the added pull through the gears when accelerating on a flat paved road.

The one thing I ran into is that with the rear chain adjuster on 7 (which I needed to get the 108link chain tightened properly), I had to have the extended piece from the adjuster pointed down as the chain guard bolt was in the way to have it pointing upwards when on 7. I am now going back and forth between leaving it pointed down or running without a chain guard. Haven't made up my mind yet.

Either way, I think if you want more power and still ride on the road some, go with 13/45, if you're doing 90% trails and don't care about high speeds, might as well go with 13/48 and still be able to run with chain guard on (and I think with the larger rear sprocket, you won't need the chain adjuster on as high a number, and will be able to get the chain tightened properly with the extended piece pointed up and not hit the chain guard bolt).

Good luck!

 

Thanks for your responses guys! Sounds like the 14/48 should go in trouble free, as it sounds like a lot of people have done it! I have already removed the chain guard from the top of the swingarm.
I am going from 13/42 to 14/48 - I would have just gone to 13/45 but my 13t CS sprocket is showing wear so I am replacing sprockets and chain to go one step lower.
I have the parts, hopefully I have some free time this weekend!
Thanks again,
TC

 

I'm not an expert on gearing, but I think the 14/48 should be pretty similar to 13/45.

 

I believe you are absolutely correct - numerically they are essentially the same. Since my front sprocket was showing signs of wear, I decided to replace sprockets and chain. I could have bought 13/45, but I understand the larger (14t) sprocket is easier on the chain in some minute way... I had no issues with the 13, but since I am replacing the front I decided to go back to 14 in case the above is true?

Thanks for the info!

TC

 

It is close, but the bigger sprockets are better from the mechanical point of view. Spreads the load over more teeth and doesn't wrap the chain as tight, both reduce the wear on the chan and sprockets. I run a 13/47 for off road use. I screwed up when breaking the chain and made it too short to run a 15/47 combination, not too bright. I started with the sort of generic 120 link DID O-ring to start, figured what I needed without thinking first, then cut the chain. I think it may fit a 14 when the chain seats in a bit... at least I hope so. It's spinning a bit over 6000 rpm at 50!

I wish a bike manufacturer would get gutsy and take a chance with a 7 speed. I rode an old Hercules GS250 (Sachs 250 engine, looked a lot like a Pento), it was a true enduro from the early 70s, first would go about anywhere and I'm thinking 7th could cruise at 70 mph or more. Just think, no more need to jockey sprockets around for what you need... such is life. They'll never do it... again.

 

Thanks KLX678, I recalled there being some motivation to stay larger on the front sprocket. I got about 3,000 trouble-free miles on the 13t and its not worn to the point of needing replacement but rounding enough to not want to use it with a new chain.

I'll heed your caution and make certain of the chain length before I cut it!!! I bought a 112, but after reading other posts, it appears that will be too long by about 2 links. I will double check before cutting!

I bought the 112 thinking that the stock 14/42 used 106, and adding 6 teeth (14/48) should need six more links???? In reality, it looks like most needed a 110? Do we know if the c/l to c/l measurement on the 07 and older is the same as the 09+?

Thanks for all the input, you guys are great,
TC

 

If I had it to do over I'd put on the largest front and rear, then cut.

 

For what it is worth, I just installed the 14/48 combo and ended up trimming one link off of the 112, and the axle is still in the forward 1/3rd of the adjustment travel.
Assuming the 112 chain actually had 112 links to start with, I am running 111 links and still have more than half of the usable adjustment range.

Having installed the Q4/Powerbomb (rejetting to 128m/38p/2T on the screw) and changing the gearing in the same week, it like a new bike! Liking it a lot!

TC