I just picked up an 01 f4i recently...had about 20,000 miles on it.... when I first got it, I noticed when riding, the bike would surge ( for lack of a better term ). Upon inspecting, I noticed that the chain was extremely loose, so I tightened.... A day or two later, I noticed the bike will doing the same so I inspected the chain further. This time i noticed if I checked the chain in one spot it would be very loose, but if i then turned the wheel halfway, it would be really tight. So with this info, I figured it was time for a new chain and sprocket. So I got a new chain and sprocket installed., the "surging" goes away. A week or so later, I check the chain and it is loose again, figure maybe the chain stretched a little, so I tightened it again.
A little more time goes by, the chain becomes loose again. Basically, nothing I do will keep the chain with the proper slack. I had an extra swingarm laying around so I pull the chain adjusters from that swingarm and put it on my bike thinking maybe something was up w/ the chain adjusters.... Finally got to the point where the chain seems to be staying at the correct adjustment but I decided to put the bike on a stand and check the chain at various points... it seems like at different spots on the chain, the chain has different amount of slack... THe chain and sprockets are brand new, so I can't imagine they have worn unevenly already...any idea what else it might be???

Sorry for long winded post.

CLiff Notes: old chain and sprockets seemed unevenly worn, replace chain and sprockets, new chain and sprockets seem to be experiencing same problem ( tight in some spots, loose in others )... HELP!

Thanks.

Mike

 

not sure how your checking the slack, so I'll tell you how I check mine, after reading up on this forum.

Put the bike in first, push it forward till 1st gear stops the bike, then check the tension on the bottom run of chain. Should be about an inch of slack.

Might not hurt to put a mark on the chain tension lock nuts to see if they are moving.

 

Bike chains stretch in different parts, so it is uneven. As you turn the rear wheel, chain is tight & then slack, happens on all bikes. Why?, cos when your accelerate your putting load on that section of the chain. load varies with the amount of force, combined with other variables (like changing down through the gears, missed gears & so on)
Wot you have to do is, rotate the rear until you find the place where the chain is the tightest, (do this several times to get it right) you then make your adjustment from there. Make sure you clean & lube your chain before making the tightning adjustment, it does make a difference. Wot it sounds like to me, is your expecting the chain tension to be consistant all the way along. its not. So if you randomly tighten it. say on the slackest section, then you have overtightned it, so wot your feeling as you ride is the overtightned sections of chain going over sprockets.