Should you run your bike without a thermostat???

[kwatts]

Noticed the other day that the fan never seemed to come on when the temp gauge indicated the engine was really hot. Took everything apart today, checked that the fan ran when the leads on the fan switch were connected with a jumper wire. Removed the thermostatic fan switch and immersed it in hot water. There was no continuity in the switch even when the water boiled. Damn…time for a new switch. Decided to remove and test the thermostat also. Guess what…no thermostat! WTH! Cannot believe the PO was running this bike without a thermostat. I have had this bike for over two months now and have put close to 2k miles on it. Is it okay to run it this way for another week until I can get a new thermostat? Or should I park it until I can get the t-stat replaced?

[Guest]

Basically no thermostat is = to one being stuck always open. Open is better than stuck closed I guess. However it would probably impactthe following

longer warm up time since the water is allwed to circulate from the moment you start the bike.

gas mileage, as the thermostat helps keep the engine at ideal temperature. When the motor is not at it ideal tem, gas mileage is impacted.

Probably not the best situation so if not your only mode of transpo, drive something else.

[MikeM]

Thermostats are cheap and you can get them at any auto parts store. The bike will run much hotter without a thermostat as the coolant is at a constant flow through the radiator. With a thermostat, the coolant gets to sit in the radiator for a while and transfer heat to the fins then the heat transfers from the fins into the air that passes through the fins. You may have heard about race cars don't have thermostats. True but that's not the whole story. No thermostat means nothing to stick closed and end a race BUT... they run a "washer" in place of the thermostat with just the right size hole for the track conditions. The washer restricts the flow so the radiator can do it's job. :wink:

[kwatts]

MikeM,

Do you happen to know which automotive thermostat is interchangeable with the one used on the 1200's? I thought I saw a post somewhere about it but cannot locate it now.

[pappy]

Try this link, I believe you will find what you are looking for.
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[kwatts]

Thanks pappy,

I knew I had seen it somewhere, just couldn't remember where. Looked everywhere but in the Parts Locator section. Forgot completely about that section.

[Guest]

The bike will run much hotter without a thermostat as the coolant is at a constant flow through the radiator.

If I'm not mistaken, and I have been a number of times, without a thermostat your motor will run cooler. The thermostat prevents the water from circulating until the temp of the coolant in the motor is up to proper limits.

[kwatts]

Walter,

I believe you are right. I had heard that same thing too. I did go to NAPA and get a Thermostat and will be putting it in today. I had a suspision that my cheapo multi-meter was not right, or that I didn't test the fan switch properly, so I rode the bike into town to get the t-stat. Much to my relief the fan came on like it should. I think the whole problem was that the connector was not seated onto the fan switch all the way. So now with the thermostat getting installed and fan working, my bike should run a lot cooler now. Thanks to everyone for the advice and help.

[MikeM]

The bike will run much hotter without a thermostat as the coolant is at a constant flow through the radiator.

If I'm not mistaken, and I have been a number of times, without a thermostat your motor will run cooler. The thermostat prevents the water from circulating until the temp of the coolant in the motor is up to proper limits.

Yes it will take longer to warm up then it will continue to get hotter than it should for the reason explained above.

[William_86]

i believe you can run your bike without the thermostat while you can get one, in case it will take a long time.


about the thermoswitch, you can just add a switch to power it on when the temp gauge reads the middle

[Guest]

Most of my experience is on V-8 car engines. I used to drag race years ago and as mentioned above some folks used a restrictor washer in place of the thermostat. The GL1200 is not a very long engine so the problem we experienced drag racing V-8's might not apply to the GL1200, I am not sure. But for a fact, if you run a big V-8 with no thermostat and no restrictor washer the rear cylinders will overheat. Without the pressure drop across the thermostat you get poor water flow to the rear cylinders. I have been an auto tech for many years and have seen street cars suffer the same problem. If run this way too long I have seen the two rear cylinders on a V-8 lose compression and start fouling the spark plugs because the rings got too hot and lost their tension.

Glad to see you got a new thermostat anyway.

[kwatts]

Yeah, I wish I had caught it earlier than I did. Lord only knows how long the PO had been running the engine without a thermostat. Now I am bummed. I will have to check the compression as soon as I can. Thanks for the info.