chain is tight and loose?

i have an 06 yz450f and an 04 zx10r. I tightened up the chain on both bikes the other day. I noticed if i turned the wheel over 180 degrees the chain would get tight then loosen again when i turn it back. It does this on both bikes so i don't think it is not lined up correctly. Any one know why this happens? Seems like the lenght of the chain would stay the same since the tire and sprockets are round.

normally a sign of a worn chain - have you measured links to see if it's in spec?

Edit - and with a worn chain comes worn sprockets - how are they looking?

this is normal, there has to be some slack in the chain to accomadate for suspension travel. overtightening the chain can cause it to fail prematurely and create excessive amounts of stress on the drive axle and bearings.

when the bike is moving the slack in the chain is pulled tight between the drive sprocket and driven sprocket, there will be some slack on the lower part of the chain. check the chain for alot of lateral play, that will indicate worn links and pins.


I don't think it's normal. It's usually a sign of a stretched chain and uneven sprocket wear in my experience.

My 10R needed new wheel bearings after 18,000 miles, some of them in places like California Speedway where you bottom out hard as you dive off the bank at about 155-160. If you're at all hard on your 10R, I bet the bearings are shot, too. On that bike, I get about 1 season from a chain and sprocket set - about 1,000 miles, and that's with a DID ERV-3 and AFAM set (15/41).

I'm not as much help with the dirtbike - I'm about to install 16/47 gearing on my 426, but it's a street 'tard. When it's a dirt/dualsport it's got 15/51, but again, the chain(s) and sprockets and bearings are all new (I bought this bike a month ago and have been replacing stuff like crazy...)

some slack is normal and necessary, excessive slack isnt normal. your service manual should tell u what the limit is

What he is describing is a chain whose slack is different from one place to the next as the wheel is turned. Not normal at all.

Mark the wheel and one point on the chain when the chain is at the loosest point. Then turn it until it's at the tightest. Note whether the tight spot synchronizes with the wheel position or the chain position. If goes with the wheel, your sprocket may be bent or worn out of round. More likely, it's the chain itself worn unevenly. You will need to replace it.

From my experience, you have a worn chain. I've had numerous chains stretch so that one spot is tight and another loose. as stated above, check the sprockets too. They should show signs as well.

ok, the way he had it described was kinda misleading, i thought he ment if he turned the wheel forward there would be slack in the chain, but if he turned it back the other way it would tighten, my mistake.... :)

when i bought my 450 the chain was worn so bad it was sawing through the frame of the bike

thankyou all for the help and advise.

The zx10r chain is not new and the sprockets show some wear but the bike has 19,000 miles on it, chain has about 10,000. the back wheel bearings are ok and everything looks straight.

The yz450 has a pretty new renthal chain and sprockets. the back sprocket is still anodized blue were the chain meets the sprocket.

OT for the forum, but...

On the 10R, the first really obvious indication the rear bearings are shot is the center spacer will become cockeyed/loose, making it tough to slide the axle through after a tire change.

Okay, back on topic:

The 16T countersprocket I have rubs against the chain guide at the front of the 426's swingarm. Looks like yours truly will live with a 15T sprocket up front.

i also have the renthal sprockets and o-ring chain. havent had any problems yet

update: looks like kz2zx hit this one on the head. The 10r beerings are shot.(Some Great OOF advise) appriciate you man!

I have ridden the yz450 since then and the chain seems to be fine now. (I am claiming gas fumes on that one). I checked everything and it is all still tight as well.



I rechecked both bikes. I rode the 450 and now the chain seems fine(claiming Gas fumes in my Garage on that one)

You were exactly correct about the 10. Bearings are bad. Thanks for the great OOF advise.

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