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zzr250 - overheat - i think i've done either head or gasket.

Discussion in 'Technical and Troubleshooting Torque' started by Mithel, Mar 22, 2007.

  1. Suggestions welcome.

    Not sure what best options are - harass the dealer or give up and go elsewhere, and if so does anyone know any reliable mechanics in burwood or sunshine area (work and home)

    Firstly - i have always used the same dealer for my maintenace and have had all sevices done at the intervals. I'm on 28000km now so major service 24000 was only around 8 weeks ago (cam chain was done at same time)

    I have had coolant pushout fairly regularly and have overheated 3 times this year. I had overheat problems last year(jan) and they put a new thermostat in (that wound up not being needed) and in the end just replaced the radiator cap. I now think it only stopped because the weather got cooler. On the first overheat this year it started leaking from the o ring at the water pump. This was replaced ($200) and system tested. this was after the 24k service

    Had trouble starting the other day, for the first time, and it missed a couple of times, backfired and then ran like a dream for two days. Was pushing coolant out still so i did a search and printed typhoons post on some tests to do (for a zzr overheat thread as well). Typhoon I owe you big time, thanks.

    This morning i did the start and pull the cap off straight away test, and had pressure, so possibly head or gasket. I then did normal pre-ride and found i've used oil since yesterday. best guess on site glass is maybe 200 ml in 80 k's.

    Now think maybe bad start was an oily plug?

    Criticisms, comments welcome, i'm gonna die being off the bike for any lenght of time, and all this while i'm tying to finalise my upgrade.
  2. yep, go to balls
  3. Many thanks Guys. I have spoken to him and he seems pretty straight up.
  4. Re: zzr250 - overheat - i think i've done either head or gas

    Have the cooling system pressure tested hot and cold. Mech will do this for you.
    I'f you've done a head or gasket it wont matter what the air temp is it will still boil.
    If the gasket is leaking coolant into a cylinder that the piston has stopped anywhere other than dead top when you switched it off it will collect coolant and you will have a water mix next time it's started. If there is enough coolant in the cylinder it will actually lock up on cranking.

    Good luck.
  5. Why isn't netriders included in "links" on balls web site?
    Just curious
  6. How does it overheat? does it reach a certain temp then suddenly climb really high. Or does it steadily increase increase and increase.
    More likely to be a gasket if its suddenly rising.

    Have u checked ur thermostat?

    Can u feel it overheating, or going by ur temp guage?
  7. Because i do 10k mixed street stop start then full length on eatern fwy, 15k, then another 10k (all approx.) it's hard to judge. it seems to do the sudden climb after i come off the fwy, but that may just be because i hit standstill traffic.

    I'm not much of a mecahnic so i haven't ventured to the thermostat yet.

    It unfortunately is not just the gauge showing the overheat. At the point the bike hits the top section of the gauge it has been throwing all the coolant out, including the header tank. Refill is about 500 to 750ml and i believe it only holds a litre.

    At the moment, i picked up some co2 colour change testing fluid yesterday and will test this weekend.
    i need to get it a mechanic to do a pressure test. That is the working pressure. i put a new radiator cap and header tank hose on last week and it still pushes past the cap tthe point of overflowing even if it doesn't boil.

    I've stopped commuting, only using it for short local jaunts. i intend to do the rest of the tests, then, depending on the results, after easter i'll retire it for a strip down and rebuild.

    2wheelsagain, yep i intend to get the tests completed in the next week. Your explanation about the coolant leaking into the cylider was valuable.

    Many thanks to you both for your input.
  8. The test fluid wil be all you need. Another indicator will be to pull the plugs, a cylinder with coolant in it will have REALLY clean spark plugs as the coolant turns to steam and cleans off deposits in teh combustion chanmer.
    I'd get teh bike nice and hot, shut it down, let it sit overnight, pull the spark plugs and crank it over. Coolant in a cylinder will be pushed out as a mist when you crank the bike over.
    If the bike is well maintained, it's probably just a head gasket, these little engines are pretty highly stressed.
    If you are losing oil, I'd expect it to be in the cooling system, check your radiator cap/radiator filler neck/overflow bottle for oil, it will be milky coloured, wipe your finger around, you'll soon feel oil.
    Also, if you are losing oil into teh cooling system, I'd expect to see coolant in the sump/oil as well. It will turn the oil milky in the sump and increase teh oil level if the leak is decent.
    ** Also, teh radiator cap in a coolant recovery system is supposed to allow coolant to flow to the overflow, it should suck back as the system cools down. It allows for expansion of the coolant as it heats. Of course, if it is blowing a lot of coolant out of the system, to teh point it doesn't recover enough coolant after the engine cools down, you have excess pressure(blown gasket).
    Regards, Andrew.
  9. not trying to hijack the thread..... but have had a overheat prob the last 3 days... jsut took fairings off and topped op radiator to have a look.... (was empty... had been dumping fluid after every ride that i noticed last 3 times) i turned bike on and saw a leak straight away :( have a leaky radiator.... so maybe check to see if its coming out when turn bike on??? mine came out straight away... not just when heated up.... might be something to check anyway....
  10. Typhoon thanks for the extra info. Definitely no oil on coolant or coolant in oil.
    I believe the push out so much into header that it doesn't pull it all back issue, is what is actually the final straw in the overheat. The fan works fine in normal circumstances, however i haven't noticed it coming on when it overheats. Not certain, but i think the sensor is bare because of the fluid push out, so fan doesn't kick in.
    Will be testing co2 today.

    Balmy thanks for your input, pressure is the enemy in my case so definitely not a leak, at least not an external one.