Honda Blackbird suddenly running very hot.

ST1100TX

ST1100TX

Joined
Aug 1, 2024
Messages
192
Age
68
Location
Kerrville, Texas
Hey all,

The other day I had my Blackbird out for a ride and it wasn't exhibiting any overly hot conditions idling for awhile in the driveway (only 220 degrees) or for the first part of the ride, but later the temps starting swinging rapidly upwards of 240+ degrees when going slow. Once it went to 258 and the numbers in the gauge were blinking. Yikes! How quickly the temps climbed was concerning and out of character even though this bike normally runs hot in slow-going. The temps would go back down to 184 once moving at around 60mph and 4K RPM. Normal temp range for the bike is between 189 and 230. The strange thing is that it didn't feel that hot from the seat and the bike didn't run any differently.

I need to pull the plastic off and check/replace my coolant, but I thought I'd get opinions on the issue before tearing into it. If I take it out again, I can always take my laser thermometer and check the temps for sure and take a look to see if the fan kicks on properly..

Could it be a faulty thermostat, low coolant level, water pump failure, radiator fan not coming on, faulty gauge, something else?

Thanks for your input!
 
My guess is the thermostat.
But if your antifreeze went low that could cause it - (curious as to how that could happen).
Also if the fan didn't kick in that could cause it.
If it is like the ST1100, you can test the fan by grounding the fan switch (on ST1100s located in the lower left corner of the radiator.)
Off the wall might be the radiator cap but I doubt it.
 
Uncle Phil said:
My guess is the thermostat.
But if your antifreeze went low that could cause it - (curious as to how that could happen).
Also if the fan didn't kick in that could cause it.
If it is like the ST1100, you can test the fan by grounding the fan switch (on ST1100s located in the lower left corner of the radiator.)
Off the wall might be the radiator cap but I doubt it.
Click to expand...
Thanks for the suggestions! I hope it's a simple solution like low coolant and/or the thermostat. Yeh, probably not the radiator cap but I'll check that.
 
The issue with low coolant is 'Where did it go in basically a closed system?'
That in itself generally leads to looking for a leak - unless someone else has an explanation for it.
I've got that very issue with one of my ST1100s but I've not pursued yet as it is probably under the carbs if I was guessing the location. ;)
 
When it gets hot it needs air to cool it, thus a need for fan at stand still. If your driving and the tstat is stuck closed or not completely opening it will over heat. Temps in normal range while driving means t'stat is working. Low coolant can act the same way but the fan has to operate (chech manual for specs) somewhere over 210.
 
Uncle Phil said:
The issue with low coolant is 'Where did it go in basically a closed system?'
That in itself generally leads to looking for a leak - unless someone else has an explanation for it.
I've got that very issue with one of my ST1100s but I've not pursued yet as it is probably under the carbs if I was guessing the location. ;)
Click to expand...
Exactly, and there are no leaks. But, Honda saw fit to cover all the routine maintenance access points up which makes it a PITA to address. At least I can say the problem is not under the carbs.)
 
I had a shadow 1100 where a fan blade was touching the shroud just enough to keep it from spinning but that would be pretty obvious.
 
Mellow said:
I had a shadow 1100 where a fan blade was touching the shroud just enough to keep it from spinning but that would be pretty obvious.
Click to expand...
That probably won't be the problem, but a fan that is not running could be. I'm going to have to remove the side cowl to see it.
 
At idle and 75 to 80 degrees, my blackbird fan cuts in at 214 degrees [displayed]. Can't recall the cut out but the fan drops it to the cut out fairly quickly. Your coolant is likely only rated for 265 degrees at 15 psig so if you're seeing 258 you're getting close to boiling at which point you lose heat transfer and you could quickly destroy things.
 
You must log in or register to reply here.
Back
Top Bottom