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New Primary Chain Free-Play Measurement Compared to Old Primary Chain Free-Play Measurement.

Discussion in 'XJ Technical Chat' started by RobbieRobot, Jan 23, 2025.

  1. RobbieRobot

    RobbieRobot Member

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    After a six week wait the new primary chain has arrived for my XJ650. I fitted it in place with a new chain guide and I measured the free play in the middle of the run from fully pushed back to fully pulled forward. The free play was 6mm. To get a comparison with two used chains that I already had, I fitted each of these in turn in the same way and took measurements using exactly the same method. The results were 22mm and 32mm. The chain with 22mm of free play only just cleared the oil spray nozzle and obviously the chain with 32mm free play interfered with the oil spray nozzle. I am quite surprised how much these Hi-Vo chains can stretch given the relatively light load that they are under. In conclusion, if you have split your crankcases for any reason I would recommend fitting a new primary chain as a matter of course. I took a photo of all three chains to show the difference in length. The new one is on the left.
     

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    RobbieRobot, Jan 23, 2025
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    cds1984 and Franz like this.
  2. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    Interesting.

    Any idea what sort of mileage was on either or both of the used chains??
     
    Dan Gardner, Jan 23, 2025
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  3. Franz

    Franz Well-Known Member

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    On a bike that is used for many short journeys over its life the chain would wear more surely? My old chain was at least 20mm deflection but was not hitting the oil spray nozzle.
     
    Franz, Jan 23, 2025
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  4. RobbieRobot

    RobbieRobot Member

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    The engine that the chain with 32mm of free play came out of had 22000 miles on the clock when I bought it plus the 6000 or so that I subsequently put on it makes about 28000 miles but I can't be sure if the 22000 recorded miles was accurate in the first place. The chain with 22mm of free play came from a bike with no speedometer so I have no idea at all of the recorded mileage.
     
    RobbieRobot, Jan 23, 2025
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  5. Franz

    Franz Well-Known Member

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    They are meant to last 150,000 miles l read on here. Only real load on it is cranking the engine.
     
    Franz, Jan 23, 2025
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  6. cds1984

    cds1984 Active Member

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    I was thinking of a way to redesign the oil spray nozzle when I did the last engine.
    Maybe a wiggle in it to give the nozzle a bit more height away from the chain.
    Seems like something that ought to be doable.
    Didn't get to it though.
    Maybe next time I split the engine!
     
    cds1984, Jan 27, 2025
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