I'm running into a problem recently, where my thermostat jammed. Does anyone here run without the thermostat in their ZXR/Balius?
Generally speaking, running without a thermostat is doable, BUT the thermostat in addition to allowing the water to reach the operating temperature also restricts flow somewhat so that the water doesn't cavitate and has sufficient time in contact with the hot metal to absorb heat and take it to the radiator, where it needs to be moving at the correct speed to dissipate the heat it's absorbed. You could continue to do it until you get a replacement
Hi Jack, it's Jack here. I know a motorcycle wrecker here in NZ and could ask about sourcing a thermostat for you if you would like. Let me know and I'm happy to cover the postage to Malaysia. Chairs
Part number is 49054-1066 for an early Balius, the ZR250 was manufactured up to 2007 in Japan Cost is about $35 USD from megazip
Depending upon ambient temperatures, running without thermostat is bad idea. This would prevent engine from running at proper temperatures. Oil should be above 100C to boil of all water that condenses inside crankcase. Without that, your oil's lubrication properties are compromised and increased wear is result. And since engine parts aren't up to operating temp, they don't fit and mesh properly, also leading to increased wear and less power.
As a temporary measure (until you get a replacement), you could drill a hole or two in the existing thermostat so that water flow is restricted enough to heat up, but still flows around the engine.
Actually, I've tried to run it without the thermostat. The bike still get overheated after about 20min of riding. There water overflows to the reservoir & the are air pockets inside. Just like you said, the water does not have sufficient time to cool down in the radiator before going into the engine. The worst is I could have cooked the head gasket at the earlier event.
Thanks for the helps man. I've found a used thermostat(with its housing) from a EL250. Will give it a try when it arrived.
I should have tried this before totally removing the thermostat. As I noticed from the radiator cap inlet(before it gets hotter), the water just runs through the radiator at a face pace. The manual said that the thermostat only opens 3mm when the water temperature reaches 85°. But the whole cooling system is already at 50° just letting the engine idle for about 5 minutes. So there is nothing could cool down the engine faster when it reaches its operating temperature. I'm just worried that i've cooked the head gasket.
Exhaust gas tester is free to rent at parts houses here, just have to pay for the fluid ($25, enough for 2 tests) Have you ran the engine with the rad cap off to see if its burping as into the cooling system, and checked for a milkshake in the oil?
ya. No burping from the cap mouth and no milkshake in the oil. Does all head gasket burn cases cause a milkshake in the oil?
No. You can mix combustion gasses and oil, combustion gasses and coolant, and oil/coolant depending on where the leak develops. Leakdown test is probably the cheapest/easiest now that I think about it.
Copied that. I will replace the thermostat first. If the situation persists, i'll get the exhaust gas tester to check. thx!
What's gauge say when water is overflowing into resevoir? Have you checked temperature of radiator by inlet port with IR thermometer? This really appear just to be weak and worn-out radiator cap. Test it to determine what pressure opens it.