640 adventure doing 50% commute ??

Discussion in 'Thumpers' started by grumpyman, Jul 3, 2013.

  1. grumpyman

    grumpyman Adventurer

    Joined:
    Jan 16, 2011
    Oddometer:
    76
    hopefully someone up in the b/trust sees this
    my buddy g/friend "helpfully" pointed out my disc lock today and bammo i have now hit the thing twice this eve
    upon rolling home from the last one a full takeoff to wreck on right side i find my 640 seems to die upon hard front braking.
    i have had a couple hints of this before but now it's bad
    as i see it my options are wait for whatever got in the wrong place to drain out and all will be better in morn
    i set my float as per motolab rec's and i think he's on the low side of things
    allthough he says i am 5 hp less than a similarly set up 640 which seem like a bit lame allthough it runs fine

    i turned up the idle and will test tomorrow and see how it goes

    rolled around this am an it still dies upon har front braking
    it does not die so much as it just starts "chugging" which i can ocaisionally cure by puling in choke more and tweeking the throttle until idle sounds regular

    up to now this bike has been great "aside from being so high"

    any ideas i am about to send it off to the shop and that always sucks
    #21
  2. bmwktmbill

    bmwktmbill Traveler

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    Grump,
    I think the common wisdom is to check the ignition switch for pulled wires...others may have another suggestion.
    bill
    #22
  3. meat popsicle

    meat popsicle Ignostic

    Joined:
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    Oddometer:
    14,263
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    If your float height is good, and your carb is clean, you should have adequate fuel pressure at the jets for hard braking. One other thing is you may have worn carb parts (time for a rebuild?), but with the scenario you said I'm wondering if you disloged some gunk and its now sloshing around intermittently clogging a jet under hard braking. I disloged some gunk from my tank (dirty gas I guess), which was obvious when I serviced the petcock.
    #23
  4. grumpyman

    grumpyman Adventurer

    Joined:
    Jan 16, 2011
    Oddometer:
    76
    his float height is 16.7 compared to 14.7 stock
    i have done creeper's carb filter setup so maybe one of the filters got full of gas and was causing some issue ???
    ran it hard (little bit of wfo and the iffy running isue have gone away)today and did some severe front braking without the chugging and dying i had yesterday
    motolab is saying i am down 5hp compared to a similar 640 and we are going to do a leak down test and see if that says the exhaust valves are crap from factory. he suspects those cause of high o2 levels (i think i am quoting him right)
    i do know the po ran way rich pilot jetting for his elevation and ktm has issues with doing there valve seats right

    question for the brain trust (creeper,meat pop,bmwbill)
    if i find crap ex valves whats the $$ diff on doing those or just doing whole top end ???? i do know the top of pistons looked a little cruddy when i looked in with the plug out... wether that has burned of with a rejet and some hard riding will need to be checked out next time i pull the tank maybe to try that rocker leak fix with the slug screw

    i did like the service i got from thumper racing on my 520 but if i can put that off for 20'000 miles i can deal with 5 hp loss as long as that doesn't lead to major failure .... can i get the valves redone for less than a full top end job ?????
    #24
  5. bmwktmbill

    bmwktmbill Traveler

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    Grump,
    How many miles on the machine?

    The damage may be a broken piston ring.

    Any oil in the airbox?

    bill
    #25
  6. grumpyman

    grumpyman Adventurer

    Joined:
    Jan 16, 2011
    Oddometer:
    76
    i learned my lesson the hard way about buying a non clean ktm
    am i looking for oil that has pushed back through the filter or is there another way in??
    broken piston ring could lead to severe failure yes?
    #26
  7. bmwktmbill

    bmwktmbill Traveler

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    Poor leakdown could be bad valves or rings or both?

    To me oil in the airbox would be worn guides or seals or both.

    When I had my head done, black oil in my airbox went away.

    bill
    #27