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ZXR250 won't start after running (cool or hot)

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by d e d, Feb 17, 2015.

  1. Hi NR's,
    Have done a fair bit of research but my particular problem seems uncommon...
    Problem has gotten progressively worse over the past ~6 months.
    Basically, the bike starts perfectly first time, every time when cold. However, once it has been running for only ~5+ minutes (like warm up and down to the local servo ~800m away, so 'cool') it won't start again for a good 15-20 minutes or so.
    If the bike is hot (after commuting home from work and filling up at the servo), it won't start for over an hour or more it seems. Then I have to push it home (like I did tonight! - bike started fine some 2.5 hours later).

    It turns over fine, just doesn't fire at all. When it's cool it sometimes will pop a tiny amount but then nothing.
    Have tried full throttle, no choke, half choke, full choke and all combinations in between and nothing changes. Time/cold temp is the only thing that will get it to start again.

    I don't know why, but I have a feeling it floods as soon as it's turned off, and thus I have to wait for the excess fuel to evaporate??
    Otherwise it could be heaps of different things from what I've read...valve clearances, plug(s)/coil(s)/CDI/etc, dirty connection(s) somewhere...

    FWIW, to me, when the bike is running it runs great, idles smoothly, revs freely and no issues through the rev range that I can notice.

    Help!!..please and thank you
  2. float valves leaking?
  3. Hey mate,
    Anything's possible....bike was made in 2000 (only 13,000km on the clock). I'm hesitant to get the carbs looked at/serviced as it can cost some serious $$$$ (and no guarantee to fix) and if it needs new rubbers/gaskets they're very difficult to find so I'm lead to believe...also, the flooding thing was just my own rough guess, I'm at a total loss TBH and I'm not nearly as well versed in engines/etc as I'd like to be.
  4. well, start with the easy things first.. "now" is always a good time to learn stuff :)

    It won't start if:
    A) there is no/weak spark (ignition bits, battery, wiring etc)
    8) there is too much fuel/not enough fuel (carbs leak fuel and floods/carbs evaporate fuel and are dry)
    C) there is no compression (valve clearances)

    for A), could be hot components (CDI/coil), dirty plugs(maybe), or unhappy battery.
    if it runs well while hot, then components might be ok (with caveat of reduced voltage)
    when starting, battery voltage decreases. if battery is marginal, then voltage to ignition may be lower, and spark too weak..
    but if it turns over just as fast as cold.. maybe not.

    if you can get hold of a multimeter, and check voltage of battery while cranking, cold and hot, that can rule out battery.

    for 8). if you have a "prime" setting on fuel tap, try turning it to that for a minute, then try to start.. that will let fuel down into fuel bowl.
    my zzr will evaporate fuel from carbs if left in hot garage for a couple of weeks.. then no start.. prime does the trick, and easy to check.

    how to check for flooding with CV carbs? not sure if full throttle start will clear it? hope someone else comments.

    valve clearances.. maybe.. they will close up when cooling.. might be hanging open a bit.
    when are they supposed to be adjusted?
  5. if you think it is a flooding issue you could try turning the petcock to off after killing the engine? then see if this helps with starting it again later.

    Can you smell fuel when trying to start it?
    • Like Like x 1
  6. My ZZR250 sometimes would behave like that.

    It wouldn't start shortly after stopping, I would just open and close the fuel cap and it would then fire up.

    Sure there was an issue somewhere but learnt to live with it.
  7. That sounds like a blocked breather tube!
  8. Hey oldcorollas,
    Huge thanks for the write-up, much appreciated. Please find my responses below.

    It seems to crank/turn-over ok hot or cold (just doesn't fire/start) and it runs fine/smooth when hot/really hot so maybe not electrical?
    Plugs are about 1 year and ~5000km old. Worth a change to see? I do think the bike runs a bit rich so maybe they will be due regardless...could be overly-fouled and contributing to the issue?

    Tried this tonight after getting home...didn't help unfortunately. Tried it normally then with full throttle, choke, both, etc....no go.

    Have tried full throttle but doesn't make an ounce of difference unfortunately.
    Valve clearances are supposed to be checked at 12,000km -- bike has ~13,000km so perhaps it's time for a major service? $$$$
  9. Hey iClint,
    Many thanks for replying.
    My fuel tap/petcock only has ON, PRI and RES. I have tried all three settings now when it won't start and none make any difference unfortunately.
    Sometimes I can smell a bit of petrol when trying to start it, but not all the time IIRC...I'm not that helpful I'm afraid!

  10. yeah, if it runs well cold and hot, then less likely to be electrical.
    if it had issues when running hot, then likely to be elec.
    5000K plugs are pretty likely to still be ok

    with Clints suggestion, did you turn to off as soon as you stopped the bike?

    if you start bike, let idle for a minute then turn off, will it restart straight away?
    how about after riding until it warms up, will it restart immediately?

    if it restarts straight away, will it not start after 1 minute? 2 minutes? 5 minutes?

    establishing a pattern may help diagnosis.

    as for valve clearances.. if they were too tight and valves leaking, then a compression test may show that up
  11. The fuel tap/petcock has no off position, unfortunately.
    Perhaps there is some sort of vacuum leak that once the bikes is off, it stuffs up the proper vacuum and floods (or something similar?)

    I will try this tomorrow night after work and see approx. how long it takes to start from hot.
    Will try cold-restarts later in the night if I get a chance.
    Will report back once I can do this.

    Iit is definitely due for a major service...perhaps there's a few little things acting up together causing this weird issue...might be the best course of action.

    Once again, huge thanks oldcorollas! Really appreciate your time.
  12. I'm just guessing mate, can't give good advice without a hands on look.

    fuel tank valve uses vacuum to open. leak will not make it flow fuel (but might make it stop)
    possible it could be stuck in open position and flood, but would also need float valves to leak for that to occur

    try the starting time, take notes, maybe we can find a pattern that makes sense :)
  13. Ok I think I may have some useful info of sorts...I think it might be the battery as the bike runs fine at any temperature when it's running and this issue has gotten progressively worse while the bike has effectively been running the same.

    Will try to be succinct as possible to save rambling on;
    - Played around trying to start it after communing home on Tuesday night...wouldn't start at 1, 5, 10, 15, 30 minute marks and I tried 2x per minute mark.
    - By 30 min mark I gave up as didn't want to flatten battery too much more and not be able to start it in the morning. Cracked the shits a little.
    - Next morning, bike wouldn't start (would turn over but not start/fire).
    - Cracked the shits, brought the bike back in and drove into work.
    - Get home Wednesday night, put battery on charger/tender (initially registered ~12.2v) and left over night.
    - Thursday morning (this morning), battery fully charged and registering ~14.2v on the battery charger/tender.
    - Put battery back in bike and it started almost instantly.
    - Get home tonight, chuck multimeter on battery while bike still running after commute home from work; showing ~11.8v and fluctuates between ~11.7v and ~11.9v give or take.
    - Rev bike a few times and voltage goes up to ~12.8v or so (forgot to check service manual to see what RPM it is in 'full charging mode'.
    - Turn bike off.
    - Battery shows ~12.2v after about 10 seconds.
    - Tried to start bike after those 10 seconds, won't fire *BUT* actually pops quite bit like it's going to start which it hasn't done previously, battery shows ~8.9v while starter is running.
    - Cease trying to start and battery goes back to ~12v and slowly climbs to ~12.2v after about 30 seconds.
    - Wait a few more minutes and try to start again, battery shows ~8.9v again while starter is running and bike pops quite a bit but doesn't start/fire, but, so close. Cease trying to start.
    - Wait about 10 minutes and try one last time; battery shows ~8.9v roughly while starter is running, but bike doesn't pop this time and starter beginning to sound weaker than the first attempt.
    - Give up, battery slowly climbs back to ~12.2v and levels out.

    Conclusion? When battery is fresh off the charger and only used for 1 day the bike gave much more promising indication it was going to start after turning off...battery stuffed even though the voltages seem to be ok (I think?) ??

    PS: Sorry for the wall of text.
  14. #14 oldcorollas, Feb 26, 2015
    Last edited: Feb 26, 2015
  15. The charge voltage sounds a bit low, when revving you should be getting 13.8 - 14.5 or so. That doesn't mean it is or isn't the battery unfortunately. You can take the battery to be tested (Batteryworld)

    One other possibility to consider is starter motor brushes. Many temperature related starting issues can be caused by bad brushes.
  16. Thanks oldcorollas!

    I haven't tried jump-starting with a car battery...this won't damage the bike yeah? Both 12v but car battery is bigger/stronger?

    I had a quick look as that PDF and pretty confusing...I think my regulator-rectifier is under the fuel tank, so will need to play around on the weekend possibly...RR is in a tricky spot...
  17. Cheers for the reply cjvfr!

    I might take in for that battery test and see what happens. First I might try that jump-start from the car and see what happens...

    Could these brushes be bad if the bike only has ~13,000km on it? (~15+ years old)
  18. yeah sorry it is a bit too confusing.. and I'm not 100% on checking reg/rec on bikes :( go easy things first as Cjvfr suggested :)

    both are 12v. car battery has much bigger capacity, so voltage will not drop as much when cranking.
    could even disconnect the bike battery altogether, and run the bike off the car bat with jumper leads.

    that won't rule out rec/reg issue.. or prove a battery issue, but if it starts hot with the car battery only, then it helps rule out other stuff like fuel and spark
    • Agree Agree x 1
  19. Good point! I will try car battery as soon as I can...maybe tomorrow if I get time and report back. Thanks!
  20. Possibly, they are a wearable part and a bike that has done a lot of start stop will have worn. Not sure with the ZXR250 if the brushes are replaceable or if you would need a reco. An Auto elec may be able to rebuild it if it turns out to be the problem. If it is a replaceable part then they are not hard to put new ones in.