Sprint Sprint Sport Hits A Top Speed Wall

Discussion in 'Sprint & Trophy' started by Rich Lympany, Aug 14, 2017.

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  1. Rich Lympany

    Rich Lympany New Member

    Jul 18, 2017
    5
    3
    Portsmouth
    Got an odd one here good people

    I did search but cant find anything that matches my issue.

    This is my first T3, it had been stood unused for a long time before having only done 15500K, and the guy I brought it off recently recommissioned her, the carbs have been ultrasonically cleaned and all fluids and some pipework replaced, however it will not rev out in top, stops about 20 mph of its max like its hit a wall. Revs to the red line in lower gears but not the higher gears (5th or 6th) seems like a fuel issue!

    One think that is odd is that I was out yesterday on its first decent run, which is where the issue was noticed, stopped off for a burger and when I restarted, pulled on the choke but forgot to turn it off all the way home and the symptoms were the same, I only noticed the choke was on when it idled at a roundabout at 3K. when almost home.
    As I said its been cleaned out, filter and all and seems to run fine through the range, its just the top end so any ideas or things to check would be great thanks.

    Since then I have changed the filter for a Pipercross element, jetted to 137.5-135-137.5 main and 42 pilot, standard needle position, carbs inspected again, fuel filters clean, tank vents clean.

    Doing my head in now. HEEEEEEEEEEEEEELP
     
  2. Rich Lympany

    Rich Lympany New Member

    Jul 18, 2017
    5
    3
    Portsmouth
    Any ideas anyone?
     
  3. Oldyam

    Oldyam Grumpy Old Git

    May 14, 2017
    613
    500
    ireland
    Only thing I would guess at is carb setup, what setting are the needles on ? did you fit a kit with new needles ?
    or just rejet ?

    If I remember correctly Dynojet do a kit with jets & needles and the needle profile is different and the needle is raised to the bottom notch + shims to add a further 1/2 groove distance of lift which would give better fuelling at max revs.

    Bear in mind that max RPM in 5th & 6th is probably the only spot that you would get full opening of the carb slide.

    Good luck with it
     
  4. Rich Lympany

    Rich Lympany New Member

    Jul 18, 2017
    5
    3
    Portsmouth
    Hi, just rejetted and the Pipercross filter, the needles are, from memory one off the bottom circlip slot and std needles, never had any adjustments till I got hold of it. It revs fully to 9K up to fourth gear
     
  5. Rich Lympany

    Rich Lympany New Member

    Jul 18, 2017
    5
    3
    Portsmouth
    Would have thought it would be good for 135 at least, it pulls strongly through the rev range, float bowls tank filters and little witch hat carb fuel line filters are clean, new tap assembly as well
     
  6. Oldyam

    Oldyam Grumpy Old Git

    May 14, 2017
    613
    500
    ireland
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  7. Callumity

    Callumity Elite Member

    Feb 25, 2017
    3,358
    800
    Nr Biggar
    Many people over oil their filters....... I would start there. It will run rich and struggle to breathe fast.
     
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  8. Sprinter

    Sprinter Kinigit

    Aug 17, 2014
    6,026
    1,000
    uk
    Isnt that a symptom of a badly adjusted clutch?
     
  9. Oldyam

    Oldyam Grumpy Old Git

    May 14, 2017
    613
    500
    ireland
    Only if the revs rise and the speed doesn't
     
    • Thanks Thanks x 1
  10. Sprinter

    Sprinter Kinigit

    Aug 17, 2014
    6,026
    1,000
    uk
    Any up date ?
     
  11. Rich Lympany

    Rich Lympany New Member

    Jul 18, 2017
    5
    3
    Portsmouth
    Valves are all reshimmed, some were micro tight but nothing to worry about but done anyway as its hit 16000 miles. Found splits in the middle rubber on the CV carb so replaced all three with new Viton rubber units, just waiting to get it back together.
     
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