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Help FZR250R 3LN5 rough running and slow to rev

Discussion in 'Yamaha 250cc In-Line 4's' started by sumthingdarkside, Mar 31, 2020.

  1. sumthingdarkside

    sumthingdarkside Member Premium Member

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    So here goes for a first post,

    A few weeks ago I was out for a ride on the old girl everything was running sweet, revved it to maybe 17k in second gear and when i changed up it no longer wanted to rev, make any power etc. Pulled over to the side of the road, no obvious windows in cases etc. Engine would still start first go on the button, no overheating, would idle at a decent rpm however it just sounds like its running on 3 cylinders and does not want to rev or make power over 9-10k. Rode the bike home parked it up and began working.

    So far have replaced all spark plugs, were a bit rich but nothing crazy, no melted pieces of metal or anything stuck to them. Have stripped, cleaned and rebuilt carbs, and have redressed the ignition leads.

    So I'm a bit stuck and was looking to see if anyone has maybe any idea where i should go for troubleshooting next as im the first to admit i dont know everything. Please find attached a video showing how the bike is running.
     
  2. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Sounds flat to me .... get a heat gun and let it warm up idling and see if all the headers are running at the same temp

    gun.jpg
     
  3. sumthingdarkside

    sumthingdarkside Member Premium Member

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    Hey thanks for the reply. Thats a good idea and i would love to do that however im in NZ and we are on lockdown for another 3 weeks so cant go out to get an IR thermometer anything I could do/check without one of those or am i best to wait, get an Ir thermometer and go from there? thanks
     
  4. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Yea just do it with your hand to get a rough idea .... obviously not contacting the hot metal ..... but u can feel them as they heat up , or if one is staying cold, easily enough

    U can get those guns on ebay .... thats if u still have a postie on duty :D
     
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  5. sumthingdarkside

    sumthingdarkside Member Premium Member

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    Okay so I did that and the headers all seem to get hot and feel like roughly the same heat coming off them?
     
  6. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    So its firing on all four then

    Have the valve clearances been done ?
     
  7. sumthingdarkside

    sumthingdarkside Member Premium Member

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    I haven't done them or had them done, no. Bike had been running fine for around 1200km from when I bought it till now if that makes any difference
     
  8. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    From what I can hear in that video and my experience owning and maintaining FZR's, your cam chain is past it's glory days. Given the state of it, it's likely that the valve clearances are suspect as well.

    From the exhaust note, it sounds to be running rich. Is it consuming a lot of fuel? A properly running and tuned FZR should do 100KM/4L (25km/l) easily.

    These carbs are known to wear out the emulsion tubes and needles which causes poor running and excessive fuel consumption. No amount of fiddling will fix worn out parts. The good news is that with Litetek seal kits and Keyster carb kits you can have it running good as new, after the valve clearances and cam chain are done.

    Also there are the pilot merge chambers in the carbs, with alloy bungs, although I've never pulled any out on my FZR's the seals are a potential issue. My GSXR250 has the same carbs more or less and I will be doing the same job, but there are no keyster kits that I can find, so it will be all OEM parts for me
     
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  9. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I would be checking all the fuel level's externally on the fuel bowl's, one may be higher than the other's
    When you cleaned the carby's, did you set the mixture's screw's then start and warm up the bike to normal operating temperature and then adjust the mixture screw's to get the best idle and response ?
     
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    Last edited: Mar 31, 2020
  10. sumthingdarkside

    sumthingdarkside Member Premium Member

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    When i cleaned the carbs i took them right apart, cleaned everything set the mixture screws back to standard and it made no difference to how it was running prior to cleaning. Throttle response has always been sharp and has not changed even with how its running now, can still snap the throttle on and off and feather it and it responds right away
     
  11. sumthingdarkside

    sumthingdarkside Member Premium Member

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    @Linkin thanks for the reply, a lot of the rattly noise from the engine seems to come from the clutch, it goes away when you pull the lever in. Is it possible the cam chain jumped a tooth?, as it went from running good to running poorly in the space of 5 seconds after a gear change. Or are these engines interference and would make a mess out of valves and pistons if that happened?

    Bike does run rich but still seems to get decent economy around 3-5l/100km depending on the riding i was doing.

    will removing the cam covers give me any indication of a problem or do I need to dive deeper than that?
     
  12. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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  13. sumthingdarkside

    sumthingdarkside Member Premium Member

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    Yes when i first purchased the bike i went through and made sure the exup was all working correctly and cables were adjusted, you can hear and see the wee motor actuate the cables and it properly moves with varied RPM.

    and sorry @GreyImport are you saying i should try pull the cam chain tensioner and make sure it is fully extending and tensioning the chain correctly?
     
  14. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Check that the cables havnt snapped or something like that and that the flap is still working as it should

    Yes read that post on the CCT .... firstly its to see if the CCT is doing its job and secondly if its at its max extension , the chain has reached the end of its life .... u dont want the CCT to be fully extending in situ
     
  15. jimv50

    jimv50 Well-Known Member

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    Or just use fresh water in a domestic spray bottle, avoids burning your hands....I know from experience
     
  16. sumthingdarkside

    sumthingdarkside Member Premium Member

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    Right I have come back bearing news, news which im unsure what to do with.

    @GreyImport i pulled the cam cover off and the chain is perfectly tensioned, and cam timing is perfectly in line with the marks on the flywheel and the cams.

    However when i pulled the stator cover off the pickup at the top was all rusty and the stator itself was also rusty, is there a chance that is the cause of the poor running?

    Also tried new fuel and filter to no avail.
     
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  17. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club Contributing Member

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    Entirely possible, you should measure the pickup against specs in the manual. The pickup works with the flywheel, the stator itself will need to be measured to see if it is faulty. Faulty voltage regulators can cause all sorts of electrical problems due to over voltage, rough running, frying components etc.
     
  18. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Sure wouldnt help

    Drown everything in Inox .... leave it for a day then take it out ... I think from memory I used very fine emery paper to clean the pickups and the inside of the 'drum' part .... and using more Inox during the process

    stator.png
     
  19. sumthingdarkside

    sumthingdarkside Member Premium Member

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    Is there a certain spec for how far the pickup needs to be from the flywheel or stator? if so would i find that in the owners supplement?
     
  20. jmw76

    jmw76 Well-Known Member Premium Member

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    Can not see that alternator problems would give the sort of symptoms you are seeing. You did say that you confirmed you have spark at every plug didn't you. Your video sounds like one cylinder not firing at all.
     
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