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Largest rear sprocket on XR250R

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I have a 2004 model and I was wondering if a 51 tooth is too large of a sprocket? I was running a 50 tooth, but just installed a 51T.

The reason I'm concerned is because I am noticing that the chain will be wearing the guide heavily. Ill take a picture asap

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The local shop I try to support and buy parts from now and then accidentally got me a 51 instead of the 50 I requested. When they gave me the sprocket and I realized it was a 51, I figured it wouldn't hurt to got one tooth bigger. After all I primarily hill climb so more gear never hurts.

But now that its on the bike I'm having second thoughts. I can't get a close up picture but here's what it is looking like:

Chain_zps588efaa5.png

The arrow is showing where I can see the chain "bending" at the back of the chain guide.

20130120_161726_zps5531b601.jpg

The arrow is showing where I can see the chain "bending" at the back of the chain guide.

Has anyone tried to run a 51? I'm guessing I will end up prematurely wearing out my chain guide....

Edited by RedBlack

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You may be able to get by with just slotting. If not, sandwich two pieces of aluminum the same thickness as the tab with super glue to make an offset bracket. Bolt through one thickness to mount to tab, and through both pieces to mount the guide. Move the guide forward slightly and notch the tab between the two bolts so the rear guide bolt can fit there.

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I raced several XR250s, changed rear sprocket sizes often, don't remember any chain guide problems.

Had sprocket sizes from 45 to 55

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That maybe but from his picture.He needs to drop back down.Also the stock guides are weak,just one big rock.Breaks off swing arm chain goes threw case.BTR

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I was looking at it more and it doesn't seem like it will cause a huge problem as it sits other than speeding up the wear on the guide a little. I was trying to visualize the aluminum plate bracket extension you mentioned earlier but don't see quite how to make that work without putting thar guide in MORE jeopardy of being torn off by a rock.

Please correct me if I'm wring

I was looking at it more and it doesn't seem like it will cause a huge problem as it sits other than speeding up the wear on the guide a little. I was trying to visualize the aluminum plate bracket extension you mentioned earlier but don't see quite how to make that work without putting thar guide in MORE jeopardy of being torn off by a rock.

Please correct me if I'm wrong

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Most guys put a plate over the whole guide.I only use the metal aftermarket ones.I have seen more then a few xrs with the chain putting a window in the case.(big Hole)

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a 50 to a 51 is less than a 2% change. that is 1/4% change in diameter in the top/bottom/front/back. If you think you are noticing way more wear, you probably did not look very close when the 50 as on there.

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