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Hmmmm, odd one today.(carb icing?)

Discussion in 'Technical and Troubleshooting Torque' started by typhoon, Jul 26, 2007.

  1. Rode the GTR in to work this morning, I knew it was close to the reserve, and had to switch to reserve about half way in. No problems there, and the bike ran at 100 km/h plus some slower riding for another 5 minutes after that.
    Now, after slowing down to 60 and following some slower traffic, I found the throttle needing to be rolled on more to maintain speed, and then got that horrible out of throttle and slowing down feeling that only a bike can provide. Pulled over, bike idled for about 15 seconds and died.
    Bike would restart after a fashion on full choke (enrichers, not choke butterflies) but would not take any throttle at all. Selceting prime and other settings had no effect, I could see fuel in the fuel filter.
    All this time, when thebike woudl run, it had that sweet exhaust smell that an engine gets when it's REALLY lean.
    Was an odd situation, plenty of fuel in the tank(visible by sloshing the bike, and definitely still plenty left from experience on this bike), pleny of fuel in the fuel lines/filter and definitely fuel getting to the carbs(choke working). The bike wasn't starving for fuel, those with multiple carbs will know that sound/feel as a carb drops out, then another etc. This just went mushy on the throttle, no warning, no surging beforehand, no dropping a cylinder etc.
    The bike started again and ran flawlessly after about five minutes sitting.
    The outside temperature was five degrees, and high humidity, so all I can put it down to is carb icing.
    So a bit of a warning, as the mornings warm up a little and there is lots of humidity, be aware of carb icing sneaking up on you. You should be fine at slow speeds and in traffic, as the engine and varying throttle settings tends to vaporise any moisture and break up any ice forming in the carbs. Icing is most prevalant when the temp is above zero, see chart below.
    Teh people who should worry are the ones who commute at a steady speed for a while, usually at low throttle settings. This gives the high pressure drop in the carbs, low heat from engine and high air velocity through the carbs which is perfect for ice formation. Also air cooled engine
    guys may have issues idling/low throttle settings.
    If your bike dies in a way that is not normal, over about 30 seconds, it's probably the problem.
    If you suspect it happens, just let the bike sit for five minutes.

    Regards, Andrew.
  2. My ZX6R suffered from it heaps. The 98 & 99's copped it heaps apparently.
  3. Yeah...I found out recently that later GTR's had coolant heating of the carbs, must be a Kwaka thing!

    Regards, Andrew.
  4. have you filled up at bungendore in the last couple tanks? i got insider info on an oopsie there ;)
  5. Nope, I am not wealthy enough to buy fuel at Bungendore! :rofl:
    I buy from the same Shell every time.
    Now I think about it though, the bike has sat outside for about a week with very little fuel in the tank, condensation could be a player here.

    Regards, Andrew.
  6. Think I experienced this the other day. Was sitting on about 80 in 5th (2500rpm) for a while and suddenly felt a little drop in power, almost like I had run out of petrol for a second or 2. I gave her some gas and she spluttered for a moment then pulled out.

    Would have been about 5 - 8 degrees and was raining ever so lightly.
  7. Andrew, are you sure your GTR doesn't have heated carbies? As I recall, the coolant passages were very narrow and were fed via a weeny little filter with a tendency to clog up, resulting in the carbs reverting to unheated :wink: .

    Might be worth a look.