(Kinda long, so please bear with me!!   )

I replaced the OEM 15T front sprocket with an inverted 14T Moose Racing XR650R sprocket at 1500 miles.  I am currently at 4100 total miles on the bike using the stock chain and stock rear 45T sprocket (2600 total miles now on the newer front 14T R-sprocket).  I really like the 14/45 combination compared to the stock 15/45 gearing, but after reading what akarob posted back in 2009, I want more.

akarob, on 05 October 2009 - 03:40 PM, said:

I am about to install a new Shinko 244 5.10x18, so I thought now would be a good time to swap out the rear sprocket with one that is 48T.  I have read numerous posts recommending replacement of both sprockets and chain, such as this one found at http://www.dansmc.com/rearchain.htm:

Dan said:

First question - Am I low enough on the mileages to get away with replacing only the rear sprocket without having to change out the front sprocket and chain??  With regard to the front sprocket / rear sprocket / drive chain combination of components, is there a general rule-of-thumb for how many miles you can go and still be able to change out individual parts without having to replace everything as a set??

I saw a recommendation from rebelventurer for a supplier on eBay named dirtparts where you can get steel front and rear JT sprockets along with an RK X-Ring Chain as a package for right at $100.  The cool thing about it is they normally set you up for what is needed for the stock configuration of your bike, yet will allow you to customize your order.  If based on the answers to my first question I find myself needing to get a new chain and front sprocket, I plan on getting the following:

14T front R-sprocket - JT Part No. JTF1307.14 (SCM415 Chromoly Steel Alloy)
48T rear L-sprocket - JT Part No. JTR301.48 (C49 High Carbon Steel)
110 link RK 520 XSO X-Ring Chain (they said they could go up or down in length, whatever is needed)

Second question - I've read about a zillion posts stating that the stock chain with 110 links will work just fine with the 14/48T gearing, but I want to get the shortest length possible in order to maximize my future range of adjustment.  Could I go as short as 108 links, or should I just stay with 110??  It seems I lost almost half of my range of adjustment when I went from a 15T front down to a 14T, but going up from a 45T rear to a 48T may offset that.

(Damn!! I'm a long-winded son-of-a-b!tch)  

I went from 14/45 to 14/48 without getting a new chain.  My adjuster was near the back with the 14/45 and moved to the front half of the adjustment range when I switched.  I then tried 15/48 (4 more teeth overall) and was able to get that to work as well, but now very close to the front of the adjustment range.

Whenever I put a new chain on, I set the adjustment right at the middle, find out how the chain fits, then decide if I want to move forward or back to get the chain in there.  I don't ever count on a significant amount of chain stretch from a quality chain.  If you'll be switching sprockets, set the chain to a length likely to work with the ones that you have.  Otherwise, you have to choose between more stable (adjustment closer to the back) or quicker steering and easier wheelies (adjustment near the front).

After closely inspecting the condition of my chain and sprockets which all appeared to be really good, I decided that I would go with just replacing the rear sprocket alone.  I went with the 48-T Sunstar steel sprocket, Part # 2-356548.  Using the new rear sprocket, 14-T front sprocket, and stock chain, I ended up with the adjusters set at the front end of the adjustment range at position 5.

For my style of riding, I am really pleased with the tighter, lower 14/48 gearing.