I've tighten up my loose chain and now I'm getting this problem. The chain appears to be lose at one point and at another it gets very tight.

Here's a video of the issue.

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Do I need to replace the chain? or the sprocket? or both. the bike now has 16,000 miles on it. I've put on about 7,000 this summer/fall.

When it's too unevenly worn, it's time to replace the chain and sprockets. You usually want to replace both things together.

If that's the original chain and sprocket it could easily be time to replace both if they haven't lubed and adjusted frequently throughout their life.

It would be better to find the tight spot - make a note of the tension, then turn the wheel and find the loose spot - and note the difference. Do this on the stand with the engine off and in neutral. Never get close to a chain/sprocket when it's spinning (in gear).

All chain/sprockets have this to a certain extent. You are looking at possible "runout" or something that would cause a change in distance from the center of the sprocket (loose mounting, elongated holes). If the sprocket was bent you'd see side-to-side movement (from the back) and not movement that would alter the chain tension.

Thx guys,

I figured I would replace sprocket and chain to fix the problem. And also change the the front 14 to 15 since I mostly do highway riding.

Are these the parts I need? Would you recommend anything better in terms of price or quality or daily riding/commuting to work? just want to double check:

http://www.amazon.com/gp/product/B0031743MU/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

http://www.amazon.com/gp/product/B000GS3OJA/ref=ox_sc_act_title_2?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

http://www.amazon.com/gp/product/B007A8OJX4/ref=ox_sc_act_title_4?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

Is it hard to replace it yourself? could 1 person realistically do it without being too mechanically inclined.

You want a part number of 1539 for the front sprocket. Since you want a 15T then it would be 1539.15.

I've never bought RK chains but I think that one looks fine.

I ran a RK XSO chain without any problems.

You'll need a chain breaking and riveting tool. Do some research and watch some videos on YouTube on how to properly rivet the master link on.

Great I'll get the the http://www.amazon.com/gp/product/B0068OCPKA/ref=ox_sc_act_title_2?ie=UTF8&psc=1&smid=A3TGC5XRRCX4P2
for the front sprocket and also the
http://www.amazon.com/gp/product/B00AUJ9DB8/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A221LQEWFFVQAG
as the riveting tool,I don't think I will be doing this again anytime soon so i don't want to spend 100bucks on it.

I've tighten up my loose chain and now I'm getting this problem. The chain appears to be lose at one point and at another it gets very tight..........

That test cannot tell you what it seems evident to you, Alex.

Note how the top of the chain is vibrating vigorously while the bottom seems tight: that is resonance produced by the engine fighting the loose mass of the tire.
Put some steady pressure on the rear brake pedal and things will become smoother.

The only way to measure the elongation of the chain and the wear of the sprockets is with the engine off.

The manual shows how to measure the chain in order to verify if its elongation has reached the specified limit or not:

Remove the chain cover or protector (to facilitate the measurement on the upper chain).
Hang a 20 lbs weight from the midpoint of the lower chain.
Measure the distance of 20 links (or 21 pins).
Repeat the measurement until the full length of the chain is covered.
If any of the distances is more than 12.7 inches (12-11/16"), the chain should be replaced.

Caveat: This will not work while links are kinked and frozen; the whole purpose of the hanging 20 lbs is to make the chain as straight as possible for measurement.

http://www.ninjette.org/forums/attachment.php?attachmentid=22307&d=1355929145

As for both sprockets:

Copied from:
http://www.dansmc.com/rearchain.htm

"You can tell if the chain is worn by pushing up on the chain in the middle (between the sprockets) with one hand, while pulling on the chain at the rear sprocket. If you can pull the chain out from the sprocket much at all, say 1/4" or more, the chain is worn out. Another way is to measure the total length of the chain, when new, and replace it when it has lengthened by 2 1/2 %. You will also find that a worn chain is hard to adjust because some spots will be tight and others loose. You will want to adjust the chain slack when the chain is at its tightest."

I got a motion pro breaker and riveter for under $70 and motion pro is quality stuff.

Dayummmm!!!! $70 I somewhat feel like a cheap ho now. I just use a dremel and vice grips. lol Dem darn rednecks... lol

Well I would still dremel off the old chain lol. The press and riveter is nice though :)