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Thread: Timing belt running of centre

  1. #1
    Join Date
    19.06.2018
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    Ducati models
    Monster s4
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    8

    Default Timing belt running of centre

    I've just changed my timing belts on a 2002 Monster S4 with the 916 engine but I've just inspected them after a few miles and noticed that the vertical belt has gone off centre! I've slacked the tention to see if this would cure it but it's still runs of center. I've place a rule across the idol and tension pulley and they are in line. But also down at the crack pulley it seems to be running in the center so my suspicions is that is it the tention pulley? I've attached a few photos to show my problem another question is that is the black pulley on the vertical correct as the horizontal is a gold colour with two guide edges on so do I have the wrong pulley on ? Thanks
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  2. #2
    Join Date
    19.12.2005
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    Forfar, Angus
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    Supersport 939, 907ie
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    Interesting. Looking at the pulleys first, I've never seen tensioner nor idler pulleys with a gold finish but that's probably a red herring. The idler pulleys should have 2 flanges (guide edges) on them but only an outer flange on the tensioner pulleys but yours all look like that anyway.
    Although laying a straight edge across the idler and tensioner pulleys shows that they are parallel to each other are they parallel to the crank and cam pulleys?
    The only other instance I have come across where one of the belts ran off-centre was a guy in the US with an ST4. It turned out that the back plate behind the pulleys wasn't square to the cam and crank pulleys for some reason. His solution was to fit a shim washer under one of the posts behind the backplate to bring it back into line. I can't remember if his needed the shim behind the idler post or the tensioner post.
    Whatever is up with yours checking the backplate might be the place to start. And are the idler and tensioner posts screwed fully home?

    Old enough to know better, young enough not to care

  3. #3
    Join Date
    19.06.2018
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    Manchester
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    8
    Hi Derek yes I've just checked that all the pulleys are parallel and also the crank is also parallel and I've also took the tention pulley off and it's sitting fully home. After looking at a few on the internet it looks like the black pulley is the correct one for the engine. Would it be worth swapping the belts over to see if it's a belt issue?

  4. #4
    Join Date
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    It's worth a try but I think it is unlikely to be the belts.

    Old enough to know better, young enough not to care

  5. #5
    Join Date
    19.06.2018
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    ****SOLVED**** After looking at a old photograph I had took I noticed the direction the tension pulley was directing its tension. This is noticeable by the nut position. So to align the timing pulley in centre of the cam pulleys the force of tension has to be towards the next pulley as the belt turns. Ive attached a wrong and correct photo notice the position of the centre nut on the tension pully. A lesson learnt by myself in taking a photo first before fitting new parts so you can refer back if you have any issues.
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  6. #6
    Join Date
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    It looks to me that in the first photo you have tensioned the belt by turning the tensioner clockwise and in the second photo it is turned anti-clockwise.
    Just as well you found that out because turning the tensioner clockwise results in the 2 runs of the belts running very close to each other and at speed they will touch. This results in destruction of the belt and the possible destruction of the engine.
    The tensioner should ALWAYS be turned in an anti-clockwise direction.

    Old enough to know better, young enough not to care

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