Just installed new 13/47 sprockets and an RK GB520GXWX 112 XW-Ring chain on my 2011 WR250R this morning. I can confirm that the 112 is the correct length chain for this combo. It moved the rear wheel back about 9/16" from where it was with the stock setup which had 8600 miles on it. This chain comes with a rivet type master link.
Did a test ride this afternoon. This is the way the bike should have been set up in the first place! I now have a lower 1st for the slow stuff, and can now actually use 6th gear without lugging the poor thing on the highway.
Edit: I wanted to add that a bigger rear sprocket will change your chain adjustment spec. If you use the stock spec with a bigger than stock sprocket, your chain will be too loose. I did the math on my 47 rear, and it adds about 2/10 inch to the spec. So the adjustment range is .51-.71 inch from the swingarm compared with the stock spec of .31-.51 inch. 5/8" falls in the middle of this range and is easy to remember.
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