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zxr250 cooling system issues

Discussion in 'Technical and Troubleshooting Torque' started by Seko, May 31, 2008.

  1. I recently bought a zxr250. The problem is that It takes a hell of a long time to heat up. The needle on the temp gauge usually sits just above cold. In stop start traffic it may go to about half but as soon as i pick up some speed, the temp drops fast.
    I replaced the thermostat today but, it didnt make any difference. Any idea what the problem may be?

  2. Are the cooling fans running continuously or cycling on and off?
  3. While servicing my friends 1989 i found that the design of the cooling system wasnt great. Air bubble would get caught all over the place.

    Tilt the bike over left and right (suggests get a friend to help), and squeeze the hoses. The bleed.
    It should help. also check the fan is operating correctly
  4. Sounds like maybe a stuck thermostat. They typically fail to teh open position. Unfortunately, they typically fail after being overheated..........

    Regards, Andrew.
  5. The fans dont switch on at all.

    Went for a short ride today, and the needle didn't budge from just over cold. I replaced the thermostat yesterday with a brand new one. Hasnt made any difference.

    It isnt over heating, its staying to cool and am worried the engine is wearing faster than it should be as a result.

    Maybe the gauge itself or the thermo sensor isnt reading the right temp?
  6. Could just be cold blooded too. My GTR will not heat up in this weather, I can see the temp needle bouncing off cold as the thermostat opens and closes. As with your bike, it needs to sit stationary to truly warm up.
    Perhaps your bke has a similar cooling system.

    Regards, Andrew.
  7. This has come up before with the same bike, and some others. I've known some to cover over half of the radiator with cardboard during winter.
  8. I use Alfoil on the GTR, easy to apply, just cut a piece oversize, and wrap teh edges tightly around radiator. Bake for 45 mins till golden.
    Covering half teh radiator does exactly SFA by the way.
    The problem with many early liquid cooled bikes is they have no cooling system bypass at the thermostat.
    What this means is that the coolant in the block cannot recirculate when teh thermostat is closed, teh thermostat pops open a lot to control this heat, and teh engine keeps sucking in cold radiator coolant in large volumes as the thermostat opens.
    With a bypass system, cold coolant is metered into teh block slowly as the thermostat doesn't pop open and closed constantly, it tends to open a little, cold coolant mixes with hot coolant, then teh really hot coolant trickles out of teh thermostat to teh radiator.

    Regards, Andrew.
  9. He's not suffering from lack of cooling (which would happen if you had air pockets) but too much cooling!

    Anyway, I think he has pulled off the trainer wheels and so I imagine that normally cornering would help release any air trapped inside, wouldn't you?

    Personally, I have never, ever had to bleed air from a system once it had warmed up, either car or motorcycle.

    All the best

    Trevor G
  10. What temps does the gauge indicate? I bet it doesn't show any figures, but if it is like the everage temp gauge, it indicates from around 70C to 120C, approx. Consequently it is not regarded as an accurate or high resolution gauge, especially since they didn't bother to print any numbers.

    In spite of what someone might have told you, since your bike does not use any sort of EFI, coolant and intake air temps are not important for normal running.

    An IC water-cooled engine does not suffer from premature wear from running cool. On systems running very lean air/fuel ratios that can lead to poor performance because a colder engine needs a richer mixture to perform at its best. However that should not cause any wear problems at all on a carburettor engine.

    The only time a cool running engine will be a problem (that I can think of at the moment) is with EFI. Then the system will tend to run richer than it should.

    All the best

    Trevor G