Chain rubbing tire?

Went for a 60 mile ride today and noticed some chain rub on the rear tire. Figured chain must be loose so I checked and its in spec (10 mm from swingarm when pushing up on chain at the designated point in yamaha service bulletin. Bike is 2010 with 5100 miles, all street, orig. Sprockets and chain, bt090 140/70/17 rear tire with 1000 miles. I'm confused, can't figure why chain started rubbing its within spec and I've actually run it looser without issue in the past. Then all of a sudden today chain starts contacting tire. Any ideas?

Thanks,
Tim

Did you check the chain adjustment stops on both sides to make sure they are at the same location?

Your chain is probably just about worn out, giving it more lateral play than its supposed to have. Mine starting eating into the tire at the tightness I always run it at when it got really worn. Since I've replaced it I haven't had an issue.

Just to note, you've got maybe 100-200 miles to swap the chain before it eats away at the chain slider underneath the swingarm pivot bolt if it hasn't already. Mine went from fine to f*cked in a 100 mile ride with the worn chain... Replace that sucker!

They are. I also measured from the swingarm pivot shaft to the axle on both sides of the bike to confirm the rear tire is properly aligned. Guess its time for a new chain. Any suggestions, I plan on keeping stock gearing as I ride almost purely street, and should I replace the sprockets at the same time even though they appear to have minimal wear?

Tthanks,
Tim

I've always replaced chain and sprockets at the same time. What looks to be not too bad is usually worse than I thought when I see the new stuff, but not always. If you were going to keep the stock sprockets for now, though I'd definitely consider a new front minimum, I'd order a stock chain from Yamaha Sports Plaza for ~$55 along with a stock front sprocket for $15ish. Don't use a breaker, use the 1pc chain as an excuse to take the swingarm off and grease the pivot bolt and other suspension linkages.

All of my replacement chains so far have been RK X-ring chains purchsed either from Dennis Kirk or ebay for about $75 with JT steel sprockets front and rear at $15-30 each, I get about 10-15k out of them in mostly street with some dirt use and not a lot of care. Stock bits I only got ~5500 miles before they wore out.