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Help CBR250 fork oil air gap

Discussion in 'Maintenance' started by trax, Jul 3, 2019.

  1. trax

    trax Active Member

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    Can someone please clarify this for me. I'm doing the fork seals on the cbr the manual states 114mm air gap but is that with or with out the spring & seatpipe? Screenshot_20190703-043421_Drive.jpg
     
  2. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I measure my fork oil with the spring and spacer in.
    But going by that picture there's no spring or spacer, and you measure it with the fork leg compressed
    @Linkin would know
     
  3. trax

    trax Active Member

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    Yeah it's not very clear just seems like it would take a hell of a lot of oil to fill it to give 114mm air gap. Bugger all came out when I stripped them.
     
  4. jmw76

    jmw76 Well-Known Member

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    I believe the oil height specification is measured with the spring and spacer removed.
    Note: the specified oil height is actually different for the various models.
    Personally, I have adapted the procedure to measure the height with forks installed in the bike.
    I support the bike, remove both caps and spacer tubes, lower the bike so the forks are at the bottom of their travel then measure down to the oil. I run about 80mm using this method. When the fork is put back together, this gives about 40 - 50mm of air space when the fork is fully compressed. You can play around a bit with the level to tune the feel of the suspension as well as changing the grade of oil. You need to run the suspension through a few cycles to ensure you get all the air out of the system before making measurements.
    Avoid putting too much oil in the fork as it will go solid before getting to full compression and could force oil past the seals.
     
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  5. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    Oil height with springs/spacers fitted or removed depends on the bike and the procedure in the service manual... but generally I just use the amount of oil listed in the specs and I've been fine so far, at least with basic forks
     
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  6. XCite Bikes

    XCite Bikes Parts and Accessories Staff Member 250cc Vendor Contributing Member

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    I normally do it without the spacer and spring, forks fully compressed, but at 140mm gap, not 114mm. I'm not sure where in the manual I saw the 140mm figure.
     
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  7. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    I have always set the level with no spring and fork fully compressed.
     
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  8. trax

    trax Active Member

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    Thanks for the input I'll do them tonight see how I go
     
  9. trax

    trax Active Member

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    So I did my forks today had a **** of a time haha. Stripped the hex head in the bottom of the fork so drilled it to use and easy out which I then proceeded to break in the hole.............
    But as far as oil height from top of the fork with spring out and fork fully down I originally went 114mm from the top as the manual states but then found this oil chart online and I ended up changing it to 95mm I hope I havnt stuffed up but see how I go. Screenshot_20190709-214912_Samsung Internet.jpg
     
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    Last edited: Jul 9, 2019
  10. jmw76

    jmw76 Well-Known Member

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    The main body of the manual states 114mm. However, you need to read the supplements which have the oil heights for the different models. You should be ok. I typically run 15W oil also.
     
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  11. trax

    trax Active Member

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    Ok, I'll ride it for a bit and see how it feels might put a heavier oil in or do the 20 cent mod haha
     
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