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Dumb chain slack question

Discussion in 'Maintenance and Servicing' started by dbrain, Aug 31, 2015.

  1. Hey,

    How much force should I be using to check the chain slack?
    Is "slack" how far it'll move with a light touch, or does it include force?

    I'm asking because I adjusted my chain yesterday to the manuals spec (13-32mm) and now the bikes making a bit of a whirring noise when I'm laying off the throttle. I'm not sure if this is new / related or if I'm thinking about it too much, but my "slack" measurements included a bit of force.

  2. Probably a little tight, back it off to about 30mm
    No force just lift the chain with your index finger in the middle of the bottom run.
    Chains are always better on the slack end of the adjustment range, you can do a lot of damage with a tight chain.
    • Agree Agree x 1
  3. As above, but also be sure you have the wheel correctly aligned in the swingarm. If the sprocket is not running parallel, you may also get the noise.
  4. Keep in mind a chain may not be stretched uniformly across it's entire length. Mark on the chain where you measured the slack area then rotate wheel till marked area is across rear cog then measure slack again. If significant variation in slack get a new chain. ( May not apply to motorbike chains these days but used to cause me problems many years ago. I would adjust slack then find the chain was too tight in places when wheel was rotated.!!)
    • Informative Informative x 1
  5. Loosened it up a bit, probably not 30mm at the tightest point but at least 25mm.
    I think it's close to aligned.. but the magical fcuking dots keep changing every time I look at them. I'm so bad a this.

    Ordered a "chain alignment tool" off of eBay that I'll hopefully get later in the week, so should help with the magical dot problem.
  6. since the force you are applying is just to take up slack/apply tension, there is a limit...
    ie, above a certain force, you aren't going to change the amount of slack measured.
    this will be the maximum possible measurement (ie furthest deflection), so adjusting slack at that force will give "tightest" chain

    if you apply less force, you get less deflection, so your adjustment will be a bit more loose. ie, may be looser than spec

    a few sites suggest a force of about 5kg (10lbs), which seems reasonable.

    are you pulling down chain as well as pushing up? push a bit, then push as hard as you can, see if it removes any more slack.
  7. Adjust the chain at the tightest point. If you adjust at a loose point then you'll be too tight at the tightest point. There's so many threads on here about chain tension (and cleaning). I found a really good video on YouTube,

    Apparently 1" to 1+1/4" (about 25-30mm) is normal for most bikes. I generally try for 30 because it can change a couple of mm when the bike is loaded with rider (probably negligible). I check it as close to half way between the front and rear sprockets as I can, at the bottom. Let the chain hang, place your finger under, press up until the chain won't go up anymore. Not much pressure, enough to lift the chain to as high as it will go. 30mm travel is what you're looking for. At least that's how I've been doing it... Very happy to be corrected.

    There's a good part on that video about how to get your wheel straight, measuring using the swingarm and axle bolts, if this was what caused your problem then maybe it will help.
  8. Thanks, I watched this before I fiddled. I went back again and have loosened it.. it's around 30mm now loosely wobbling it. I think I may end up topping myself if I keep fighting with it tonight.
    I *think* I'm a bit closer to accurate on the dot measurement system. It's hard to tell because one side is shiney while the other isn't. I will verify when the chain adjustment tool comes in.
    The swingarm to axle bolt measurement doesn't really work for my bike, as there's an exhaust in the way of getting an accurate measurement.

    Anyway, I'll stop bugging you guys. Thanks heaps for the help!
  9. Hmmm. Another method I've seen is to put a laser against the sprocket and point it at every link along the chain whilst against the sprocket, and it should hit the same point on each link - this tells you your chain is perfectly in line with your sprocket. Not everyone's got a straightedge with a laser attached to it though. Alternatively,you could use a 600mm ruler and rest it against the back sprocket pointing towards the front one and check the distance from the ruler to the chain is uniform along the length of the ruler. Exhaust may be in the way for this method too.

    Don't forget to spray a little lube on while you're down there :p
  10. A noob but here's my 20c worth. My bike has a notched cam for adjusting the chain so you can only adjust it in steps. I could either have it at factory max of ~40mm which to me was too slack, so I set it to the next which put it at the min of about 20mm, maybe less. Got it serviced a couple of days later and noticed they'd slacked it off to the 40mm notch. So looser limit is as suggested typical.
  11. Which bike is that Al? Every one I've looked at has screws at the back of the swing arms so you can adjust with a bit more finesse? Surely there's an elongated hole in the swingarm that your axle bolt goes through? I am astounded they only give you 20mm steps. That seems ridiculous
  12. I'm not sure if yours works like mine, but I have "dots", presumably same dealy as your notches. You can move things by part of a dot.
    So e.g. mine is at about "4 and a half dots" on each side at this point.

    If I had to move by a full dot every time I'd either be super tight or super loose, which sounds like what you're seeing.
  13. Steve VtecSteve Vtec The bike is Yamaha YZF-R15 2011 model. No screw adjuster. What it has is an off centre cam with round notches, a bit like gear teeth which pivots on the axle - one on each side. and a slotted axle hole. There is a spigot on each swing arm towards the front of the bike. To adjust loosen the axle nuts and move it back and forth, rotate the cams and locate on the same notch on either side, push the wheel forward to seat the notches on the spigots. Tighten axle nuts, which on one side makes the cam try to rotate to loosen of course.:mad: I guess the idea is that by using the same notch on both sides and making sure you push the axle forward to seat both cams on the spigots then the wheel is aligned. Down side is that the tension is adjusted in steps. I guess you could back it off one notch looser and then move the wheel back to tighten the chain a little as if you had a basic slotted swing arm but then you have the problem of loosing wheel alignment as you tighten the nuts - or I would. Gues I should try it. I notice the new model has screw micro adjusters. Yellow is Cam, red dot is spigot:

    r15 rear axle 1.
    • Like Like x 1
  14. Seating the cam in the notches stops the cam from rotating as you torque it up. I've tried putting the cams a the peak of a tooth. There are holes in the cam and a hole in the back of the swing arm. but they never seem to line up to allow inserting something in there to stop the cam rotating as I torque the axle nuts to the he-man spec. I guess it doesn't matter if a cam rotates on the swing arm as long as I can keep the wheel aligned. The notches are deeper and the peaks are sharper than that extract from the manual. And yes often one notch is too loose and the next is too tight. P**ck of a design or at least it is for this user.
  15. It's fine to be at the loose end of the range, preferable if you use most of your available swingarm travel. Much past the stated adjustment range on most machines can get you into trouble as well, but going UNDER the range WILL cause damage. The notches on the cams and marks on swingarms aren't always reliable in terms of alignment, either, and you need to verify them before you trust them.

    One method that's effective is to use ratchet straps to compress the rear suspension so that the front sprocket, swingarm pivot and rear sprocket are all aligned ie the point where the chain is tightest, and set the chain tension there. If you do that you have to remember two things. 1 back off the suspension pre-load before you start, and 2 this is the TIGHTEST point so you don't want lots of slack, just enough so that it's not binding in the tight spots in the chain. When you take the straps off again you should have the right about of slack with the bike on the stand. Note: if this doesn't make sense to you, don't try it. Having the chain too tight or way too loose can cause serious damage, accidents, injury, and maybe even the current government getting back in after the election.
    • Like Like x 1
    • Funny Funny x 1
    • Informative Informative x 1
  16. If you are worried get your mechanic to look at the chain. If they need to adjust it its only $10 or so or maybe free and you'll see how to do it and what it should be. Noise might be somewhere else. I had it a while back (also have a street triple) running hard into corners and it was still there after I got a new chain. I'll listen for it next time I get out. (Don't go so hard in the wet and cold roads though). What chain lube do you use? I use Motul factory line chain lube and apply it every 2nd tank of fuel.