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Help ZXR250 1994, Will idle perfect, only revs to 12k then stops running

Discussion in 'Kawasaki 250cc In-line 4's' started by timmeh01, Mar 20, 2015.

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  1. timmeh01

    timmeh01 Member

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    When i first bought it I took it for a ride. it was running but wouldn't rev past 10k. Then the more I tried to rev it, the less it could rev till it stopped and wouldn't start. I took the carbies off, cleaned them well, put in petrol filters and a new air filter.

    I tried to start the bike and the same problem happened. It was idling like a dream for around two minutes. I then took it for a ride at 4-7krevs for 20 seconds. I then tried to rev it higher. It first went to 12, then to 7, then it wouldnt rev / shut off. Once it shut off, I couldn't start it again. I left it for 10 minutes or so and tried to start it again. It was showing signs of wanting to start with full throttle on but didn't. Then the battery seemed to be about to give up so I put it on charge.

    My guesses are blocked fuel lines, or a vacuum forming in the tank? But I am sort of stumped. Does anyone have any advice?
     
    timmeh01, Mar 20, 2015
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  2. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Start with the basics.

    Is the bike stock? Are you running pod filters?

    Check your carb boots and airbox boots. Set the pilot screws on the carbs to stock. Check slide operation of the carbs. Check throttle bodies.

    Clarify what you mean when you say the bike won't start. Does it turn over but not start? Or it won't crank?

    Your carbs may have blocked jets, larger jets than stock, worn needles & emulsion tubes causing richness/flooding/bogging
     
    Linkin, Mar 20, 2015
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  3. timmeh01

    timmeh01 Member

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    It turns over but won't start (you can hear it wanting to, but it doesn't). The bike / everything is stock. It has a uniflow filter. I will be pulling it apart tomorrow to do some more investigating
     
    timmeh01, Mar 20, 2015
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  4. timmeh01

    timmeh01 Member

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    Couldn't resist. I just tried to start it then and it started up easily and idled nicely (only had it on for about 5 seconds). (This is about 1 hr after it decided to stop running). So far initial plan is to run it tomorrow and rev it and see what happens with the fuel tank open
     
    Last edited: Mar 20, 2015
    timmeh01, Mar 20, 2015
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  5. Mclaren

    Mclaren Well-Known Member Contributing Member

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    Sound like something blocking the carbs I would pull apart clean everything throughly and reassembly
    Use threebond carby cleaner and throw in a new carb kit from litetek Blair the man for that
    Remember it only needs to be a poofteen of crap to block up jets and could be clearing and blocking
     
    Mclaren, Mar 20, 2015
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  6. timmeh01

    timmeh01 Member

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    Yeah thats very true :( Part of the fun I guess!
     
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    timmeh01, Mar 20, 2015
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  7. kiffsta

    kiffsta Senior Member

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    if you have a vacuum, you should hear the pressure release when you open the tank, there is a breather in the tank and I you can use some whipper snipper line to flush it out. To validate this, you could get it in a position where it wont run, then open the fuel cap and try again.

    The lads have covered most of things I would look at above, check the petcock , if they have sat for a while, there might be junk in the petcock filters. If you have an in-line fuel filter, then check that as well, I have seen them fitted back to front. The air mix screws could be out as well, they should be 2.5 to 2 3/4 turns out , or it could be the carby floats not set right.

    Start at the petcock and work your way down.

    Be careful when reassembling the air box, the 8mm brass crews that hold the air box to the carby are weak and snap if you apply too much muscle to them.



    Good luck

    Chris
     
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    kiffsta, Mar 20, 2015
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  8. timmeh01

    timmeh01 Member

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    Thanks so much guys! I will give it all a go tomorrow
     
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    timmeh01, Mar 21, 2015
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  9. timmeh01

    timmeh01 Member

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    Havn't tried to fix yet. This is a video I took this morning of it working / not working after being revved
     
    timmeh01, Mar 21, 2015
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  10. MashtX

    MashtX Well-Known Member

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    Oh damn :/ that's not a healthy sound.
    It's not leaning out up high is it? Doesn't sound like anything super nasty like bad valves (hopefully)
     
    MashtX, Mar 22, 2015
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  11. Mclaren

    Mclaren Well-Known Member Contributing Member

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    I would rebuild carbs to start with cost bugger all and eliminates them also check plugs have spark and mayb clean out ur tank
     
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    Mclaren, Mar 22, 2015
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  12. Joker

    Joker See "about me" for contact details. Contributing Member

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    I'd second what Chris said and look at your fuel petcock first, aren't these a vacuum petcock...? if it is faulty you're getting starved of fuel (that's what it sounds like..)?

    You could then progress onto fuel lines, needle valves, main jets etc but if you've cleaned your carbies properly (or at least had some sort of decent go at it) it should run better than it sounds like it does.

    The bike behaving strangely (like vacuum in the tank and other complicated theories) are possible, don't get me wrong - but save yourself the hassle and check the simple things first :)
     
    Joker, Mar 22, 2015
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  13. timmeh01

    timmeh01 Member

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    I had a play around today. I didn't look at the petcock but it seems the vacuum valve may be running poorly / very poorly (top of this picture http://www23.tok2.com/home/sil40/img021.jpg). Hard to tell if its making any reasonable suction. My mate who was working on it seems pretty confident this is the problem. Will keep working and hopefully find a solution!
     
    timmeh01, Mar 22, 2015
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  14. thebeefsalad

    thebeefsalad Well-Known Member

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    Looks like your vacuum tubes are from 1994. Have you looked for dry-rot?
     
    thebeefsalad, Mar 23, 2015
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  15. timmeh01

    timmeh01 Member

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    Will be pulling it apart tonight!
     
    timmeh01, Mar 23, 2015
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  16. timmeh01

    timmeh01 Member

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    Latest update: All carbies cleaned. All fuel lines cleaned. Petcock cleaned. 'vacuum valve' as in picture above cleaned. A hose from the vacuum valve was never connected to the airbox so I think that may have resulted in not enough fuel making it to the carbies when the bike was revving high. Connected everything and turns out the petcock was on prime instead of reserve so I believe I drowned the engine. Let it sit for half a day and tried again. Wouldnt start. Checked spark plugs and they were all dead / fouled -_-. Getting new spark plugs and will try again! Lots of learning involved here.
     
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    timmeh01, Mar 27, 2015
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  17. timmeh01

    timmeh01 Member

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    So. Carbie cleaned twice. Fuel pump cleaned. Spark plugs changed. Petcock working fine. Still does the same thing. Will rev up like in the video and then slowly die. Once its died, it won't want to start again for 10-20 mins. I took it for a quick ride in first and second at around 6-8krpm, after about 30 secs it didnt want to go above 4kpm and I just made it back to the garage. It makes me think its still a fuel issue. Perhaps something more sinister with the carbie? On my bike, the diaphragms may be screwed. When its idling they don't sit there moving/wobbling like they do in this video but they do move when I rev it - . Any other suggestions?
     
    timmeh01, Mar 29, 2015
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  18. kiffsta

    kiffsta Senior Member

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    Why do you have a fuel pump? Zxrs are gravity fed, maybe that's your issue ?
     
    kiffsta, Mar 29, 2015
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  19. timmeh01

    timmeh01 Member

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    haha. its not a fuel pump thats just what some people have been calling it. its a 'vacuum valve' as far as the manual is concerned
     
    timmeh01, Mar 29, 2015
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  20. kiffsta

    kiffsta Senior Member

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    Okay cool, what are your air fuel mix screws set at ?

    When you stripped the carbs, did you check the jet sizes ?
     
    kiffsta, Mar 29, 2015
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