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Front sprocket change "chain slack" question

Discussion in 'Maintenance and Servicing' started by DamusB, Mar 19, 2015.

  1. quick question to anyone that knows hard facts. I am changing front sprocket to 1 tooth down but what I want to know is when I do it, will it matter how much slack is on the top or bottom of the chain when i put it back on, should it be flat on top and lose down the bottom or how many links should be free at top or bottom ect. Every youtube video i watched its just not mentioned as if it doesnt matter like "yep put the chain on.... here we go.... done" like whatever goes??? is it as long as it fits on its all good?

    also my service manual said it should be .6 - 1 inch of slackness, seems pretty tight and when I do my tension that tight i start hearing strange noises, any advice?

  2. You will have to loosen the back wheel including undoing the chain adjustment bolts first, then do the front sprocket swap then tighten the chain adjustment bolts so that the midway point of chain moves up down the factory spec you mention. You measure the slack on the bottom chain with light pull down and then a light pull up. measure is from same point on chain eg bottom side of chain. Tighten chain adjustment bolts evenly, that is do one side of bike then do the same number of turn on the other side till your axel adjustment markings are the same and the chain slack is at correct measurement.
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  3. An inch sounds about right. That is from pulled up to pulled down. If your chain makes noises, check it to see if there are any stuck links that do not straighten. It may be time for a new chain too.
  4. Ahh I I get it, great advice! Ok thats what I will do, thank you
  5. When replacing sprockets you may have to replace the chain also.If you chain has stretched you may adjust it to the required tension in one place,and could be too tight or loose elsewhere.
  6. i think chain slack should be measured at the midpoint of the bottom of the chain with someone sitting on the bike. if theres 1 inch of slack with no rider, there will be less than that when someone is sitting on it. possibly explaining funny noises.

    having your chain too tight is way worse for the bike than too loose. there can be tight spots and loose spots in chains, its good to rotate the wheel and check the free play at several points and ensure there is sufficient slack throughout the travel.
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    • Agree Agree x 1
  7. if you read you bike manual it will say how to do it.
    My manual says to put bike on side stand and measure. It does not say on center stand, or on paddock stand OR with someone sitting on it.

    Yes you are right that if you sit on the bike then the 3 points of interest are all aligned (front sprocket bolt, swing arm bolt, rear axle bolt) that make the chain reach it max working tension - but then what is the slack measurement here ???

    The techs have already worked it out and factored in the bikes weight resting on the side stand.

    Chain need to run with slack.

    as mentioned before there might be some issues with the old chain, loose/worn pins, missing o-rings, tight links. these will all make a chain loud!
    • Agree Agree x 1
  8. There is a great site called Gear Comander that has all sorts of "what-if" figures for changing sprockets, I use it all the time, gives hundreds of different figures from how many links to remove to how far out the speedo will be. Just type in your bike specs and what you want to change:

  9. healtech speedohealer or 12oclocklabs speedoDRD is your friend for fixing up the speedo after changing the gearing.
  10. the speedo is geared from the front wheel so it shouldnt be a problem
  11. How do you know its geared from front wheel?
  12. i have one.
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  13. Hahaha thats a good enough source for me!!!
  14. lol. another good source of info is 2fiftycc.com.