How hot does your bike run?

[Leonardo Lupo]

I have no temp gauge, is your radiator too hot to touch for long after 3 mins of minutes of idle? What is an easy way to see if my cooling system works without waiting to see if the bike smells like burning plastic?

[DannoXYZ]

Idle is worse case scenario because of zero air-flow through radiator. Many decades ago when I did lots of commuting in city stop-n-go traffic, I'd have switch connected to radiator fan so I could manually turn on fan if I knew I'd be stopped for a while.

Get one of these and measure some numbers: https://www.amazon.com/dp/B08CXX63ZD/

[Leonardo Lupo]

Yep, my fan doesn't even turn on, I think it's because the gauge cluster has been removed?? I need to figure out the wiring for that and throw a switch in as well.

[Leonardo Lupo]

Made a short plug so that if I ever need fan permanently on I can unplug the "fan switch" at radiator and plug into the short. Mounted it on top of stock plug with cable tie. Trying to keep everything stock so will hold value when sold.

[DannoXYZ]

Cluster doesn't have anything to do with fan. Two completely different circuits that don't have anything to do with each other. Dash warning light is driven by sensor in thermostat housing.


Fan is driven by thermoswitch in radiator. Test fan thermoswitch in pot of water brought to boil. Note temperature when switch closes. Compare to number given in manual.

Does fan turn on when you short thermoswitch connector?

[Leonardo Lupo]

Originally Posted by DannoXYZ

Cluster doesn't have anything to do with fan. Two completely different circuits that don't have anything to do with each other. Dash warning light is driven by sensor in thermostat housing.


Fan is driven by thermoswitch in radiator. Test fan thermoswitch in pot of water brought to boil. Note temperature when switch closes. Compare to number given in manual.

Does fan turn on when you short thermoswitch connector?

Yes and yes

[DannoXYZ]

At what temperature does fan thermoswitch connect contacts?

If it's within spec given in manual, just put everything back together and it should work like stock. Temperatures may hot have gotten hot enough to activate fan earlier. With infrared thermometer, you'd know for sure exactly what temperature coolant is in radiator around thermoswitch.

You can also get slightly lower-temp thermoswitch if you want.

[Leonardo Lupo]

Originally Posted by DannoXYZ

At what temperature does fan thermoswitch connect contacts?

If it's within spec given in manual, just put everything back together and it should work like stock. Temperatures may hot have gotten hot enough to activate fan earlier. With infrared thermometer, you'd know for sure exactly what temperature coolant is in radiator around thermoswitch.

You can also get slightly lower-temp thermoswitch if you want.

Switch is very broken. I could. Would like to keep manual anyway as I might need to have manual control in 40C+ weather.

[Triple Jim]

Originally Posted by Leonardo Lupo

Switch is very broken. I could. Would like to keep manual anyway as I might need to have manual control in 40C+ weather.

If the system is working properly, you never need to manually control the fan. It turns on when it's needed and off when it's not.

[thedrewski86]

Originally Posted by Triple Jim

If the system is working properly, you never need to manually control the fan. It turns on when it's needed and off when it's not.

I'm glad you said it. The manual fan switches bug me; they're great when you remember it, sucks when you forget. Kawasaki designed the system to work w/o rider intervention.

[DannoXYZ]

Manual switch should only be to supplement an already-working system. That is, everything is working fine in stock automatic condition if you leave switch off.

Manual switch should never ever be used to replace thermoswitch that's not working. At least replace thermoswitch with working one 1st so system works as designed.

[Leonardo Lupo]

Originally Posted by Triple Jim

If the system is working properly, you never need to manually control the fan. It turns on when it's needed and off when it's not.

Originally Posted by DannoXYZ

Manual switch should only be to supplement an already-working system. That is, everything is working fine in stock automatic condition if you leave switch off.

Manua switch should never ever be used to replace thermoswitch that's not working. At least replace thermoswitch with working one 1st so system works as designed.

Originally Posted by thedrewski86

I'm glad you said it. The manual fan switches bug me; they're great when you remember it, sucks when you forget. Kawasaki designed the system to work w/o rider intervention.

I agree, the switch should be fixed and manual control should only supplement the working engineered system. Ordering part now.

[Triple Jim]

Originally Posted by Leonardo Lupo

I agree, the switch should be fixed and manual control should only supplement the working engineered system. Ordering part now.

When would the properly working fan system need to be supplemented? If the coolant temperature gets high enough to turn on the fan, the fan runs. Any running of the fan more than that only overcools the engine, and that doesn't help anything.

[Leonardo Lupo]

Originally Posted by Triple Jim

When would the properly working fan system need to be supplemented? If the coolant temperature gets high enough to turn on the fan, the fan runs. Any running of the fan more than that only overcools the engine, and that doesn't help anything.

For example when the engine is off and I need to cool it down. It will be over 110 Fahrenheit. Another example would be if the switch breaks.

[Triple Jim]

Originally Posted by Leonardo Lupo

For example when the engine is off and I need to cool it down. It will be over 110 Fahrenheit. Another example would be if the switch breaks.

When the engine is off, running the fan won't do much, since the engine's water pump is not running.

If the fan thermostat fails it just means you can't run the engine with the bike not moving, or moving very slowly, until you replace the switch. If that does happen and you really need to ride very slowly, as in heavy traffic, you can just take any scrap of wire and short the thermostat contacts together. The thermostats don't fail very often though. Mine have never given me any trouble on any motorcycle.

[Bob KellyIII]

I understand Leonardo's concern... being able to turn on the fan when idling at a stop would be a good thing ! just to keep the bike from over heating...
but I really don't think that is necessary .
if your going to stop turn the bike off ! don't keep it running to get hot ! ....
....if your making a desert machine where you know you'll be running is extreme heat, change the thermostat hook the fan to be on at all times with the key switch and pray it's enough to cool the beast before the pistons melt !
which is probably over kill.... but you could do it that way !
under normal riding conditions even HOT summers, the cooling system in it's stock form works great !
but 2 up in the outback in extreme heat, in deep sand ,...all bets are off !
....
Bob......

[jkv45]

Just run a good synthetic oil, and don't worry about high temps.

A water-cooled engine, with an operating cooling system, and synthetic oil can run extremely hot without any issues.

Conventional oil will breakdown from heat. Synthetic won't.

Engines like to be hot.

[Triple Jim]

For a liquid cooled engine to actually get too hot, the coolant has to boil. You'll see steam coming out. As Jay just said, engines like to be hot. Ring and cylinder wear is reduced at 200F+ and efficiency is higher.

[DannoXYZ]

Yup, engine oil itself has to run above 100C to boil off all water condensation in crankcase. Thermal efficiency is better at higher-temps. Limit is materials durability.

Honda's working on some all-ceramic engine with no cooling system. Higher heat inside combustion-chamber and no losses to water-jacket. Would be awesome if it's 2-stroke as well, but Honda hates 2-strokes.