Causes of excessive chain guide wear

Discussion in 'The Garage' started by BigWally, Oct 10, 2019.

  1. BigWally

    BigWally Been here awhile

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    396
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    The chain guide on my ‘18 KTM 500 EXC is worn and needs replacement already at 100 hours/2800 miles. Seems like premature/excessive wear compared to other thumpers I’ve owned. I’m OCD regarding chain maintenance and tension and have sag properly adjusted. Suspension professionally lowered 1.5”. Anybody have authoritative info as to causes of premature chain guide wear?
    #1
  2. TripleTriples

    TripleTriples Been here awhile

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    Did you put a smaller sprocket out front? Maybe ride in sand a lot?

    Seems like it should last longer than that.
    #2
  3. BigWally

    BigWally Been here awhile

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    3A65E634-E82C-4B6E-BADC-651E382266D2.jpeg OEM 14T front sprocket. Negligible sand riding but that will change. I did put on a larger 48T rear sprocket (OEM 45).
    Read another inmates comment regarding excessive chain guide wear on his 500 which prompted me to check mine. Worn thru the light colored inner liner on the bottom.
    Ordered an Acerbis chain guide & 2 replacement slider blocks.
    #3
  4. MrPulldown

    MrPulldown Long timer

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    That is your problem. Bigger sprocket bigger diameter; puts the chains at a lower path. On my bike it came with 2 chain guide mounting brackets. Not exactly came with 2, but there was a dirt and a dual sport (street) versions of the bike that had different gears 41/43 and 47/49 depending on years. The lower geared dirt version had a bracket that shifts the chain guide forward so that it rides at a location where the chain is higher. I often swap between the lower and higher rear sprocket depending on riding conditions. With a sprocket swap a chain guide mount swap is necessary.
    [​IMG]
    [​IMG]

    The vertical space your guide has available for the chain is very small. Would think that an aftermarket guide will have a bigger allowance. I personally wouldn't worry about it till it broke. That amount of wear probably fixed your issue and you won't get much additional wear.
    #4
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  5. BigWally

    BigWally Been here awhile

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    That makes sense. Thanks!
    The Acerbis chain guide I ordered has 2 rear mounting holes to accommodate small/larger rear sprocket sizes, which will be helpful and worth paying attention to. Glad I didn’t just order another OEM cuz it woulda quickly been chewed through again.
    #5
  6. greasyfatman

    greasyfatman Long timer

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    What bike came with that? Great forethought.
    #6
  7. MrPulldown

    MrPulldown Long timer

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    Dr350 and 250. I actually think it could have been an after thought. The 250 and 350 dirt came with low gearing. "Oh crap the suzuki parts bin chain guide doesn't fit." Easier to make a different mount than guide.
    #7
  8. BigWally

    BigWally Been here awhile

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    396
    Location:
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    E9113D73-60D7-4027-B858-0BA6A880E844.jpeg D209C230-3717-440A-9D05-14F0B10106A9.jpeg 8561C19E-6164-4624-9464-9A9EA48DF0A3.jpeg 48T mounted (45 OEM).
    First pic with rear chain guide mounted in higher/45 position shows chain path too high onto sprocket which would lead to excessive wear of the replaceable slider block until its (overly) worn in.
    2nd & 3rd pics with rear guide mount in lower position for larger sprockets. Much straighter chain path onto sprocket which should improve chain guide and drivetrain longevity.
    As the RMA video said its a noisy chunk of new nylon until its worn in which probably won’t take long.
    #8
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