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Project Bought a ZXR250C.

Discussion in 'Your 250cc Projects' started by Linkin, Jan 30, 2017.

  1. TonyZXR

    TonyZXR Well-Known Member

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    Nice gauge setup . Might have to borrow it
    for a day .:lolsign: Also how did you adjust the mixture screws ,special tool?
     
  2. ShaneP

    ShaneP Well-Known Member

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    Did you check valve clearances in the end? Though I think that rattle sounds like gearbox - when you pull the clutch in does it reduce the noise? It goes when you rev the engine, could be a wave in the timing chain. Idle is 25 revs per second, top end is 12.5, so it should be a faster rattle if the issue is there.

    P.S. if you switch the vac gauge to "dynamic" you can see if your valve clearances are different, and if you have the info, probably be able to know by how much.​
     
  3. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    With a little snap on flat blade screwdriver and a few burns from the radiator hoses

    I did valve clearances, timing chain, tensioner when I first bought the bike. Then I did clutch fibres, plates, springs and now the basket. Balanced the carbs on 3 separate occasions now. I am probably due for valve clearances again.

    I did flick the gauges onto dynamic briefly and everything looked fairly even

    I noticed that with all the vacuum stuff blocked off for balancing, and leaving the vac line for the fuel tap open to atmosphere, it revved a lot cleaner off idle.

    I think my next step will be to remove the primitive emissions doodad (fresh air valve) and fit a gravity fuel tap.
     
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  4. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    Shane, are you referring to Linkin or me in this post? My rattle goes away when bike is in gear and under load.
     
  5. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    As does mine
     
  6. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    Do the Bearings ever make a rattle? I'm wondering if they're on their way out? The only other thing for me to do is split the cases and check everything for tolerances and spec. Not something I'm in a hurry to do.

    RHS Bearing.jpg
     
  7. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Me either.

    While the basket was off, we checked the shaft, bearings felt totally smooth. Still leaves the other shaft though.

    In that photo, it looks like the head and bores are still attached. Can you just flip the motor and take the bottom off? If so, that's awesome... unlike the FZR motors where you have to take the head and bores off.
     
  8. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    Yes, ZXR engine can be split that way. Was there any movement in the shaft? Normally, it's the other side bearing (drive shaft) that goes, but this rattle has me stumped. Anyone care to comment? Shane's Big-end bush issue doesn't sound (to me) like a rattle maker. More like a knock maker and an engine killer.
     
  9. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    I big end bearing that is shot wont rattle.. it will be more of a knock and while it may be there at idle it would be most noticeable on dropping revs after giving it a big rev with no load..
    Once you have heard a bid end about to go.. you never forget the noise.. ask me how I know :oops:
     
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  10. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Yeah I know that sound, this was my R6 that let a big end go, it also had a cracked cylinder which was the cause of its blowby problems.

    RNRjImE.jpg

    wG0ygdq.jpg
     
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  11. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    So, we're no closer to tracking down the rattle. I guess Linkin has checked solid plates for warpage and anything else clutch related?
     
  12. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    They were all replaced
     
  13. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    You would have to think it is in the geartrain if the rattle goes away when you pull on the clutch...
     
  14. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Not quite. Since replacing the other clutch compontents (bearing, rod for the pressure plate, and the arm in the clutch cover) the clutch is very quiet.

    This noise only disappears when in gear and you load up the clutch (ie holding the front brake while stationary).

    On the move, it doesn't rattle at all.
     
  15. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    That is EXACTLY what I have.
     
  16. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Like this?

     
  17. Andych

    Andych Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    You would still have to think it is in the geartrain... just exactly where will most likely remain a mystery unless either of you splits the crankcase and finds something obvious inside.
     
  18. Murdo

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

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    Cannot be the drive shaft bearing as that only turns when chain moving/riding.
     
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  19. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    Pretty much. @Murdo was there when we fired it up. The rattle wasn't there previously when we fired the engine in the frame a couple of months ago. Only seems like a recent occurrence and seemed to get worse quickly. Dr. Murdo (Stethoscope in hand) checked it and it's definitely coming from the RHS of the engine. We thought cam chain tensioner failure or cam chain issue until I pulled in the clutch, put it in gear and eased it to take-up...and the rattle disappeared. I've had a quick look, but everything is where it should be, so I'll have to split it and have a look.
     
  20. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    I am now thinking it could the positive neutral finder mechanism...
     
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