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overheating & plug fouling

Discussion in 'Technical and Troubleshooting Torque' started by zoot, Jul 27, 2007.

  1. CBR900RR , 94 model, I ride it to work, about 40 mins each way every day . In the last 2-3 months it has overheated & the plugs fouled ( I am assuming ) on 3 occasions. Once was in terrible traffic, but yesterday it did it in really mild traffic. The temp guage is not hitting the red, maybe 3/4 , & then it starts running really rough at low revs in the stop start traffic. After stopping & giving a rest & then riding with no traffic it seems OK . 1 time it was completely screwed & needed the plugs changed , but that was also due to dodgy fuel I believe .

    Has anyone got any suggestions as to what I can do to avoid this, as it not exactly hot & I am not looking forward to summer if this is what it is like in winter . I don't think this should be happening in mild traffic on a 40 min ride??

    Any thoughts appreciated.
  2. Anyone able to advise how to check that your radiator fan is working properly ?
  3. Not too sure about the fouling of plugs, but it almost sounds like you have air trapped in your coolant system. The easiest way to deal with it is to drain your coolant and top it up, make sure you use the bleed points (if any). Another technique that helps is to "massage" the various tubes, this seems to get air out, but don't press too hard or fast otherwise you'll be pulsing coolant out.

    Radiator fan can be checked by getting a workshop manual, and checking the troubleshooting guide :p

    The fan is usually operated by a cutoff switch, If you know the operating voltage of the fan, and there are only two electrical connections to the fan, find out which one is positive and apply a power source. If the fan spins, that works and it might be a thermostat problem.
  4. check vacuum lines and fuel lines. You may be leaning the mixture due to bad connections.

    Are the plugs fouled black or burnt whitish?
  5. That doesn't sound particularly hot to me, probably only around 100C.

    I would be more inclined to think it was a fuelling problem.
  6. What makes you think its over heating? It sounds to me like its running rich after a while. Time for a carb service? Are all plugs fouled? How much oil does the engine use?
  7. I'm having exactly the same issue on my Speed Triple - running rough at lower RPM's, when riding in heavy traffic and temp is at about 100degC

    Maybe there's some bad fuel circulating at the moment...
  8. sounds alot like my ute really, would get up to heat, start running rough, that was a blown head gasket, one clylinder would eventually fill with water, stoping it from firing, whole ute would shake as it missfired
  9. About 6 weeks ago all the carbs were checked & cleaned & new plugs fitted, so they all shoudl be OK . The reason I think it is related to overheating is because it tends to happen when the temp is rising ( though not in the red ) & I can feel the heat in my legs down near the engine ( maybe thats a part of it ! ) . When it happens I can actually smell fuel, which leads me to think too much fuel is getting to the carbs for some reason ?? Why this only happens when cummuting & stop start I don't know.

    I rode last week for 500K's on twisties & freeways & its all fine, goes great, but in the bad traffic its not much chop!!?? :(
  10. I think that maybe the heating and fuelling issues are separate.

    That's a normal temp for a bike to get in traffic/city riding.

    A thought: As suggested above check the fuel tank vacuum lines. When the bike heats up (as it is normally in traffic), this heat can often make the fuel vacuum lines more flexible, allowing them to become crimped by the tank/obstruction, with the engine running badly as a consequence.

    I've seen this happen on other bikes, worth checking out.
  11. When was the last time you had the system flushed and new coolant put in ??
  12. I am not sure when the coolant was last changed/ flushed, as I bought the bike only 3 months ago. I will be looking at that this weekend & checking the rad fan , after that look at fueling issues I guess.
  13. I suspect you are not fouling plugs, but perhaps suffering from the fuel vapourising once the temp gets up on the motor. This will cause the low rpm rough running you describe, and once cooled for a while will run normally.

    The other possibility is a head gasket, or cracked head, and once heated the compression/water leaks with an expanding gap somewhere.
  14. O.K, if the bike is not spewing coolant, and returns to normal running once it is cooled down a bit, we can eliminate a head gasket.
    Sounds to me, as said above, like you have a problem with fuel vaporising in either your carburettor bowls or fuel lines.
    If it is fouling plugs(did you actually verify fouled plugs by loking at them?) then it could be that fuel is boiling in the carb bowls or you have a nedle and seat issue in teh carbs. Odd for all of them to do it though.
    have you checked your coolant level as mentioned above, and the level in the overflow tank?
    Have you checked the electric fan comes on? I bet it does, as I think that is the heat you feel on your leg. Start the bike and let it idle till it gets to 3/4 hot, and see if the fan comes on then get back to us.
    I did a big writeup on cooling issues a while ago now, see if you can search for it.
    Oop here it is! Amazing what a quick, simple search will turn up! :roll:
    Regards, Andrew.
  15. OK the fan works fine & the coolant levels are fine & all teh hoses , caps etc are fine. I think its carbie related, I read up in my worshop manual & in the troubleshooting guide it describes such issues with carbie as fault type thing. I guess I now decide if I actually USE my workshop maunal or pay someone to do it . Its shit cos when its going fine its so good, I love it , then it goes bad on me & shits me.
  16. Zoot, you haven't confirmed what the plugs look like yet.
  17. Take off the tank and check your vacuum hose/s and fuel lines...

    20 minute job at most.
  18. Cammo, you win the web diagnosis award . last nite I filled her up & as soon as I started her there was trouble. The force of the petrol going into the tank had obviously been the last straw for the hose, it was dripping fuel badly & the old girl wasnt going anywhere. So I guess when she has been heating up the hose has maybe been expanding & fuel was escaping, I remember smelling it actually , and that was why she wasnt running at low revs sometimes. So anyway , unfortunately I didnt make it to the weekend when I might have tried my lame arse hand at checking out the hoses & saved myself some $ by fixing it myself. Glad I found out what it was , shoudl be easy to get sorted out now. Thanks all for your valuable suggestions & contributions
  19. OIH! Read reply number 3. :LOL:
  20. Oh alright, your all champions!! iBlast you can have a special award for persitance. Next time it dies you can all come to my place & fight over who can fix it first!