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  1. #1
    Antiguan FZR's Avatar
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    Fzr-broken timing chain

    Well it never ends, my 54hour FZR was running great, no more clutch issues, rotax clutch doing its job then, Sunday @7000RPM it just died, no strange sounds. Got it back on the trailer, pulled the valve cover and the chain was gone.

    I figure this is related to my clutch failure, some debris might have streched the chain although when I inspected there was no signs of damage??

    Going to pull the head tonight, do you guys think it touched down?


  2. #2
    desperado's Avatar
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    Quote Originally Posted by Antiguan FZR View Post
    Well it never ends, my 54hour FZR was running great, no more clutch issues, rotax clutch doing its job then, Sunday @7000RPM it just died, no strange sounds. Got it back on the trailer, pulled the valve cover and the chain was gone.

    I figure this is related to my clutch failure, some debris might have streched the chain although when I inspected there was no signs of damage??

    Going to pull the head tonight, do you guys think it touched down?
    I have seen that happenned before. The chain on this engine is relatively undersized. High rate of rpm acceleration plus stiffer springs will put a fair amount load on that tinny chain. Typical dammage will be a few bent valves. Normally pistons are ok. You will need to unlock all valves and inspect for straightness. What valve springs were you running?

  3. #3
    Antiguan FZR's Avatar
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    I am running the stock valve springs turning 8300RPM with a R2.

    Do you ever see damage to the valve guides?

  4. #4
    hitman's Avatar
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    Wow. That really sucks. First I have heard of a broken timing chain. Hopefully it's all laying in the bottom and didn't break apart sending pieces all over.

  5. #5
    desperado's Avatar
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    Quote Originally Posted by Antiguan FZR View Post
    I am running the stock valve springs turning 8300RPM with a R2.

    Do you ever see damage to the valve guides?
    Sometimes, but most times not. It depends how hard some valves may have hit. The "positive" thing about a timing chain failure is the fact the cams are free to turn in any direction after the chain is off the sprocket and therefore the valves will only lightly kiss the pistons with the cams changing position after every impact. I have reassembled an engine that suffered a broken chain and the only dammage was 2 intake valves and one exhaust valve. The engine has logged 35 hours after the repair without any issue. The trick is to inspect all valves very carefully and replace those that have bent or which are out of spec. I have only seen 2 engines with a broken timing chain.... not frequent but certainly not imposible as you are the 3rd one I am aware of.

  6. #6
    dawson's Avatar
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    only broken timing chains i have seen and heard of have been after people have had the cam tensioner out and have incorrectly reinstalled putting too much tension on the chain eventually in just gives up and snaps

  7. #7
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    It's not a interference motor so don't worry about bent valves.
    Also you do not need to pull the head to change the chain.

  8. #8
    It's not the destination, it's the journey!! Rip'nTear SHO's Avatar
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    Damn...sry to hear that man. Well with the power your making.....and the rougher riding you guys submit ur skis to in the islands....your pretty much giving that thing a beating that alot of other skis wont see...a worst possible scenario with very fast rates of accel/decel during pump unhooks and re-hooks.

    As I'll be beating mine up offshore as well....thank you for sharing this and putting it on my radar. Maybe a heavier-duty chain will be developed sometime in the future.

    Hope your up and running again soon.

  9. #9
    Kristian Keppel Waterholics's Avatar
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    I'm still trying to figure out how but something similar like this happen to my ski just with alot more damage. We think it's due to over revs though. Apparently my valves floated and idk how it happened but the timing chain, head, cams, valve guides, valve seals, cotter valves, lifter valves all got damaged when it happened.

  10. #10
    desperado's Avatar
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    Quote Originally Posted by JIM'S PERFORMANCE View Post
    It's not a interference motor so don't worry about bent valves.
    Also you do not need to pull the head to change the chain.
    HO cams will make the valves lightly kiss the pistons if running JE's forged, been there & done that. Have a few pics if that's of any interest.

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