Gear shift drum failure
  • hrc450x
    Posts: 5
    Joined: Mon Oct 07, 2013 6:28 am

    Gear shift drum failure

    by hrc450x » Thu Aug 17, 2017 1:17 pm

    Hey Guys

    I have recently had a transmission failure for the second time on my 2010 CRF450X the first time was fair enough as i had it wide open on the bitumen and clicked 5th gear without the clutch and it went bang, and wouldn't hold 5th gear just jumped in and out of gear, i was still able to ride it home as no other gears were affected.
    Once i disassembled the trans i found a fair peice broken out of the shift drum right at the end of the groove, i replace the drum about 3 gears due to wear on the dogs all the forks and every bearing in the engine/trans plus clips and thrusts. Now about 2 years later and not a whole lot of hours its gone again on a mx track after a jump it seemed to go into neutral so i went to select a gear a bang rear wheel locked solid engine continued to run on disassembley ive found another failed shift drum but this time alot worse,

    What i would like to work out is this a result of the dogs not engaging correctly and jumping over each other and driving the fork back into the shift drum coursing the failure?

    Am i to hard on the gear selector?

    Or if u have a good look at the photo of where the shift drum has failed could it be a manufacturing/design fault as there is no material at all where the cracks started?
  • hrc450x
    Posts: 5
    Joined: Mon Oct 07, 2013 6:28 am

    Re: Gear shift drum failure

    by hrc450x » Thu Aug 17, 2017 1:25 pm

    Lol bugger puc to large wont let me post it
    Last edited by hrc450x on Thu Aug 17, 2017 1:31 pm, edited 1 time in total.
  • hrc450x
    Posts: 5
    Joined: Mon Oct 07, 2013 6:28 am

    Re: Gear shift drum failure

    by hrc450x » Thu Aug 17, 2017 1:29 pm

    20170818_061510_resized_1.jpg
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  • User avatar
    JimDirt
    Posts: 4406
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: Gear shift drum failure

    by JimDirt » Thu Aug 17, 2017 9:31 pm

    That looks like a clean break , so it means a force had to make it fail as opposed to damage over time , i guess the first question would be is how do you actually shift ?? , are you holding the throttle and just banging into gear ?? , or are you slightly relaxing on the throttle and then shifting ?? , as this lessens the load on the gears almost completely , it's kind of like shifting a Semi ,you can shift without the clutch as long as you are working the throttle to load and unload the transmission's pressure on the gear so it will glide out of that one and into the next one , i could shift my Toyota pickup without the clutch and i do it with a Dodge Diesel pickup as well , it's not that hard once you learn the correct procedure , i do it with both my bikes all the time , i rarely use the clutch while moving weather trail riding or on the MX track , its all a matter of relieving the load before attempting to shift , in other words if you have to put force into it , or push hard with your foot to shift , then you're doing it wrong and this is what is causing the failures you're having
    2020 CRF450R
    2006 CRF450X
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    Weiser , Idaho

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