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Overheating Hornet 250?

Discussion in 'Modifications and Projects' at netrider.net.au started by Mango, Jun 17, 2006.

  1. I have a HOnda Hornet 250 - 1998 model.. im looking to get some advice on how to fix my bike. ITS OVERHEATING

    Things i have done so far include -

    replaced the fan and water pump
    replaced thermal control unit (radiator sensor)
    removed thermostat unit (spring) to have constant coolant flow
    put an override switch to manually place radiator fan "ON" at all times
    flushed my radiator

    and it still overheats.... anyone got any other ideas?? Desperately needed advice on mechanical things i could try!!


  2. maybe not rev/ride it soo hard when riding :LOL: :LOL:

    but if thats the case could be the radiator itself or maybe a water pump issue.....(im not sure if the hornet has a water pump)
    or could be the hosing somewhere maybe

    hope that helps
  3. Firstly, put the thermostat back in. It doesn't do the engine any favours with fluctuating temperatures, and the bike won't run any cooler without it, just takes longer to get up to temp.

    I reckon it's also unnecessary to wire the fan up to a switch, it should be normally coming on at >98C, and won't cool the engine down more by switching it on before this.

    You can test that the thermostat is working by dropping it in a pot of boiling water.

    You've replaced/tried the obvious there's not really much left to do.

    The cooling system may have an airlock in it. This will make the bike run hot simply because there's not enough coolant. Best thing to do is to run the bike with the rad cap off standing the bike up right at standstill and keep squeezing each of the hoses to force the air out , dont rev the bike just keep it at idle, have some spare water standing by, because as the air comes out it will force water out as well.

    How thoroughly did you flush the radiator? Clogged up radiators are the most common cause of overheating IMO. Keep running a garden hose through it until the water runs clear.

    Are the cooling fins on the radiators bent/mashed? This can also contribute to overheating. You can straighten them up by inserting a cable tie between each one.

    Also be sure that the bike is actually overheating and that the guage isn't just faulty.

    The bike will run much cooler when up to speed, if it still continues to overheat, the worst thing you could possibly do is be sitting in traffic/standstill. The water pumps are also nearly non-existent at idle on 250's due to the large rev range that they need to operate over, so it too doesn't help much when idling.

    Good luck!
  4. Cammo, you're dead right on every count, very methodical :grin:
  5. Cheesr Paul, owning a V4 has made me very familar with overheating problems!