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gsxr 750 doesn't want to downshift sometimes

Discussion in 'Tech' started by rymerc, Aug 13, 2024.

  1. rymerc

    rymerc Well-Known Member

    My old 2006 gsxr 750 doesn't want to come down from 6th into 3rd or 4th at the end of the back straight lately. If I leave it in 5th and downshift at the next corner it works fine, but it costs me a ton of drive. It does this maybe 10% of the time when being pushed. It's fine early in sessions.

    Only does it at one point at my home track, and seems to do it more if I use the aftermarket quick-shifter (upshift only) on that long straight. I almost never use the quick shifter.

    I've tried Rotella T6 and Mobile 4T and no change.
    Bike is at about 9500 miles, 2k of which is track mileage. No recent changes, crashes, mods.

    Just plain worn out? Known issue? I suck at shifting all of a sudden?
     
  2. DBConz

    DBConz Registered Idiot

    have you removed the shift selector & rod and reinstalled it? if you're off by a tooth it wont like to change gears.
    quick shifter or using the clutch?
    have you measured your friction plates and steels for thickness?
    are the steels blue?
    how is your cable slack on the clutch cable?
    have you ever adjusted your clutch and slipper from the access hole in the side case cover?
     
  3. rymerc

    rymerc Well-Known Member

    I have removed and reinstalled the shifter selector and rod, it was indexed 1 spline off from the mark. I can reinstall it on the mark and use the adjustments to put the lever height where it needs to be and give that a try.

    Using the clutch to downshift, usually using clutch to upshift but occasionally using the quickshifter to upshift

    Have not measured plates at all or checked for blueness

    Clutch cable is slightly slack, I measured 9mm of free play at the end of the clutch hand lever

    Have never adjusted the clutch or slipper from the access hole, I can read up on that

    Thanks for the suggestions
     
  4. DBConz

    DBConz Registered Idiot

    neither videos mention that you're supposed to have the cable slack completely in to make it as loose as you can at the lever.
    service manual says to back these out 1/4 - 1/2 turn once the touch. i do mine 1/2 a turn, and adjust it after every race weekend.
    you'll need a 19mm socket to open the access panel. to get all 3 of the slipper adjusters, you'll want to turn the motor. so open the smaller access hole on that case cover with a 10mm allen and a 14mm socket to turn the motor.

    for the clutch (center with the Phillips screw head):

    you'll need two 12mm wrenches and a phillips screwdriver

    for the 3 slipper nuts:

    but back it out 1/2 a turn, do not do 2 1/4 like he said.
    you'll need a 10mm wrench and a 4mm allen key
     
    kirk erlinger likes this.
  5. DBConz

    DBConz Registered Idiot

    i use a sharpie to make a line to make it more obvious as that imprinted dot can be tough to spot sometimes. i run into issues often as i'm off by a tooth once i get that clamp fully tightened down and realize i'm off by a tooth
     
  6. rymerc

    rymerc Well-Known Member

    Thanks, I can handle that.
     
  7. DBConz

    DBConz Registered Idiot

    it may not fix your issue, but it'll certainly ride much smoother on downshifts
     
    rymerc likes this.
  8. TurboBlew

    TurboBlew Registers Abusers

    shift forks are wear items...
     
  9. ibidu1

    ibidu1 Well-Known Member

    I would loosen the adjuster ride and extend it, you can also go a notch up to match the shifter location. But like Turboblew said could be shift forks, it can also be a shifter drum. I remember on the older ones the bolt would back out on the shifter drum and cause similar shifting. I would try spreading open the adjusters, and if that doesnt work, pop open the side cover and see if theres play in the shifter drum or arms
     
    rymerc likes this.
  10. RM Racing

    RM Racing Tool user

    Middle shift fork may be bent. Common.
     
  11. Shenanigans

    Shenanigans in Mr.Rogers neighborhood

    Stomp the shit out of it like Clarence did. LOL
     
  12. dave3593

    dave3593 What I know about opera I learned from Bugs Bunny

    Those are good oils but the fact that it acts up later (it's fine in early sessions) may indicate a viscosity issue as temperature rises. One of my Husqvarnas would only shift right with a certain oil after i tried several.

    It wanted stuff on the more viscose side. You may consider trying something on the thicker side of the recommended range. The problem transmission I mentioned liked Bel-Ray.
     
    Last edited: Aug 14, 2024
  13. dave3593

    dave3593 What I know about opera I learned from Bugs Bunny

    Both of the oils you mentioned have a zink additive. It is a benefit for certain types of loads. There is a possibility that linkage doesn't like it.
     
  14. Banditracer

    Banditracer Dogs - because people suck

    What weight oil are you using ?
     
  15. rymerc

    rymerc Well-Known Member

    I've ran rotella t6 5w40 in this thing for a few years, and just threw in the Mobil1 4t 10w40. I change my oil after 2ish track days so it's always pretty fresh. I'd definitely be down to try a heavier oil or bel-ray, easy and cheap compared to the alternative.

    Bent shift fork is scary. I can knock out a 1 hour job no prob, but having to drop the motor and pull the trans makes me want to cruise the classifieds.
     
  16. dave3593

    dave3593 What I know about opera I learned from Bugs Bunny

    If it just developed this problem recently but are using the same oil, than an oil change probably won't help.

    I'm sure you were already thinking that.
     
  17. Boman Forklift

    Boman Forklift Well-Known Member

    I don’t know a GSXR motor, but I’ve changed forks on a dragbike at the track by dropping the pan and pulling some covers. So you may not need to remove the motor and split the cases?
     
  18. Steeltoe

    Steeltoe What's my move?

    :eek:

    Not saying that's your problem but I am saying this is part of regular maintenance.

    upload_2024-8-22_17-37-7.png
     
  19. TommyD

    TommyD Well-Known Member

    rotella I can't speak on.
    when customers come in with smoked clutches I always ask what oil has been used.more often than not I am told mobil 1.could be coincidence might not be.
    I sell alot of motul and am always told that it makes there bikes shift better than it ever has.
    your mileage may very
     
  20. rymerc

    rymerc Well-Known Member

    I adjusted the clutch and slipper and damnit if a big nasty pile-up on lap 2 didn't mangle the bike pretty badly.
    thanks for the advice, not sure this one will get put back together.
     

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