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Everything posted by chopp666

  1. Hi chaps...thanks for all the info into my 1/4 throttle problems. but i STILL have them! this is whats wrong. bike starts and runs FINE, if you slowly roll the throttle on when the motors nice and warm at 1/4 throttle it "machine guns" out of the exhaust and won't pick up AT ALL. i've cleaned the carb with spray carb cleaner and compressed air, clean filter, swapt the carb for another, changed the cdi, coil and plug, checked the kill switch for grounding, checked all wiring for shorts, changed the fuel and even changed the tank! checked for broken valve springs, checked can chain timing by going to TDC ( line on fly wheel pointing to 12oclock ,piston at tdc and camchain wheel marks at 9 and 3 oclock ,flush with cylinder head) ALL is fine and in tiptop condition....i've removed the auto decompesor just in case and am about to put it all back to gether to see if that has made any difference ! i have a nice spark as it starts up fine! all i can think of now is maybe a bent or sticking valve or burnt valve seat! any more ideas ! thanks chaps ...chopp
  2. chopp666

    '91 XR600 1/4 throttle mayhem!

    hi all....no it runs like shite from 1/4 throttle to WOT, you get a missing/machine gunning noise from the pipe! and it will not pick up! if you snapp the throttle to wide open it's the same, it'll rev up then start to miss and will just sit there miss fireing at about 2000rpm ! next step is to pull the head apart and check for burnt valve, cracked piston etc etc.....:-( chopp
  3. chopp666

    '91 XR600 1/4 throttle mayhem!

    thanks Tool..i'll try that and see what happens...chopp.
  4. Hi all...i have a '91 XR 600 , single carb model . it was running fine but has suddenly developed a realy bad misfire at anything over 1/4 throttle, with slight black exhaust smoke. have checked the carb, CDI, coil, plug, fuel and thats all fine....it's like almost valve bounce or riding with the choke half up! i am a very good mechanic and have checked all the obvious things but no luck! any ideas out there ? thanks chopp
  5. chopp666

    xr600 misfire at 1/4 throttle

    ....hmmm, the plug is black but dry and sooty, not wet.Pulling the the cam cover is the next thing to do tomorrow night after work! funnily enough the bike was running great yesterday , had a good 4hour hard trail ride in slippery mud and fast road 80/90mph ,bike was fine when i turned if off . In the morning i washed it with a garden hose and brush , and it was a pig to start , and when it did it had the 1/4 throttle problem! ...thanks for the info on checking the cam timing, i'll do that and let you know...cheers chopp