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OMG...what's that noise???

Discussion in 'XJ Technical Chat' started by redcentre003, Oct 17, 2010.

  1. redcentre003

    redcentre003 Member

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    Well...with the first sign of warm weather the other day I thought I'd go for a nice little ride in the country, maybe stop by for a coffee and danish, then amble back home in the perfect 25degC day.

    Then, almost at the little picture perfect country town every time I revved the engine past 3500rpm this horrible metal noise came from what seemed like...everywhere!

    I slowed down and it disappeared. I sped up and it started and then got louder. The engine? Couldn't tell...it was like metal balls rattling really fast in a metal cannister. I stopped. I idled. No noise. I revved the engine at standstill...no noise. I hop on the bike and there it is...at 3500rpm.

    Not wanting to chance damaging the engine I headed home at a leisurely pace and waited anxiously for the next day when I had a chance to look at it.

    Well...finally tracked it down. Relief...a loose baffle in the exhaust outlet of the 4 into 1's! It seems that the fibreglass wool packing material had slowly disintegrated from when I last repacked the muffler causing the innards to start vibrating and rattling metal to metal at what must have been its harmonic frequency.

    A quick repacking with new material and she was as silent and smooth turbine like as a new bike...well nearly new.

    I recall that someone used coarse stainless steel scourer pads around the baffle of their XJ. Would be interested to know whether this lasts and whether it has the effect of reducing noise very much at all. The fibreglass really doers silence the exhaust but then it is much denser than the stainless steel scourer/mesh.

    Happy riding.
     
  2. SLKid

    SLKid Active Member

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    Nice! Glad you figured it out! I hate that "not knowing wtf that is" Syndrome. Why... is she DOING that, lol. Been there done that :D Thanks for the share
    -Chris
    Ride safe
     
  3. Robert

    Robert Active Member

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    I am relieved to hear it was something fairly innocuous! I'll bet "the boys" wanted to head home when you heard that!
     
  4. wizard

    wizard Active Member

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    'Twas I, on the suggestion of Polock.
    Verdict: it lasts well, it doesn't quieten much, but the exhaust note is awesome.
     
  5. redcentre003

    redcentre003 Member

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    Thanks for the feedback guys.

    Riding on 2 wheels and hearing noises coming from below can be a worrying experience - have to keep your eyes on the road - can't look down or back even briefly to see if you can pinpoint the noise. Wearing a helmet seems to disperse the sound so that it seems like it's coming from places that it's not.

    Warm weather this weekend so will look forward to completing the ride this time.

    I think I'll stick with the fibre/wool packing in the exhaust - I kinda like the turbine sound/feel. The old stuff had compressed and blackened over time and the exhaust did have that "awesome" sound when wound up.

    1985 XJ900 still going strong - summer holiday project is to stiffen up the front suspension from it's soft floaty feel.

    Rid on into the sunset...
     

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