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Correct chain tension measurement technique

Discussion in 'The Garage' started by G_YamTech_314, Oct 17, 2020.

  1. Something that has been bothering me since buying a new motorcycle has been the correct way to measure the tension of a chain.

    In school I had issues getting proper chain measurements in agreeance to the instructors standards because she felt it should be (for example) 25mm of movement without the top part of the chain flexing at all...

    I felt that you should move the chain entirely through it's motion and measure the distance traveled.

    In the pictures I'm about to show you'll find the two techniques displayed. What are your thoughts on this?

    Picture one. Chain tension at cold, resting height on side stand 70mm mark for baseline

    Picture two:top of chain at the baseline. You can use the nylon chain slider as reference to compare the movement of the top of the chain.

    Picture three: results of measuring chain tension with NO TOP CHAIN MOVEMENT (got between 25-30mm with very little to no flex in the top half of the chain)

    That's the result of testing chain tension with no top half chain movement. If I do the same test by measuring at baseline, and pushing until the chain stops, the same motorcycle with no adjustment measures as follows:

    Picture one:showing the difference between top chain movement at nylon chain slider
    Probably a 5-10 mm gap between the slider and the chain at full tension

    Picture two (still comparing this number to a baseline of 70mm) pressing upward on chain to measure distance traveled to calculate chain tension:
    Nearly 50mm of chain movement with this method. So either the chain is 2x looser than the recommended tension of 30 mm, or it's just right.

    How do YOU measure? And what do you recommend??
  2. 5twins

    5twins XS650 Guru Top Contributor

    Maybe because I've been doing it for so long, I don't measure, I just go by "feel". But, there are a couple important points to take into account. First, chains stretch unevenly so there will be tighter and looser spots. For this reason, you need to check the tension in several spots, just in case where you set it happened to be one of the loose ones. Then it would be too tight at a "tight" spot.

    Second important point is you must check the tension with weight on the bike, with you seated on it. With you on it, the shocks compress, the swingarm lifts up, and the chain gets tighter.

    So, my routine is to adjust the chain with the bike on the centerstand, setting it a little looser than I'd like. With the rear wheel elevated, I can spin it and find a tight spot to set it at. Then, I take the bike off the stand, sit on it, and reach down and "feel" the tension. Then I roll ahead a few feet, reach down, check it again, roll ahead some more, etc.
  3. motormike

    motormike XS650 Junkie XS650.com Supporter Top Contributor

    I find the tight spot... there usually is one.... then.. off the center stand.. with my generous kister on the bike.. test..then make needed adjustments.. As I roll up to park the bike..... about 50 feet or so..I shut the bike off.... coast.. and listen... for any noise that's abnormal that I can't hear while the bike is running...
    gggGary and G_YamTech_314 like this.
  4. So you're saying if I can hear the chain moving on the rear sprocket it's probably too loose?
    Greyandridin likes this.
  5. 5twins

    5twins XS650 Guru Top Contributor

    Not necessarily, it might just be dry and in need of some lube.
  6. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    Loose you might hear it hit swing arm or a rub block, tight you tend to hear hard chain releases from the sprocket teeth. Rolling a tight chain backwards is a pretty good worn chain/sprockets test, they protest loudly and jerk as the chain pops free of the hooked teeth.

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