Radiator and thermostat housing question

Hello,

Need to pick your brains.
The bike is an 88 fzr 1000.
They come with radiator and the fairly ugly thermostat housing.

I am doing some custom stuff on the bike and want to get rid of it.

My limited understanding of this part is:
Fill radiator with fluid (because it has the cap)
Over flow point for excessive coolant
Thermostat monitors temp and which then triggers the fan somewhere.

Is this correct?

I am thinking about replacing the radiator with one that has a cap already built in.
My aftermarket gauge comes with thermostat that measures coolant temp. I could use this to trigger the fan (either turn it on manually or come up with something).
This leaves me with the overflow.
Do you know if other radiators have that built in anywhere?

I hope the above makes sense.
And here a pic of what I am talking about and would like to get rid of...

 

The thermostat restricts coolant flow until the bike reaches operating temperature, at which point the thermostat gradually opens and allows the coolant to flow freely through the radiator. For street use you cannot realistically get rid of the thermostat, or the thermostat housing. If you run without a thermostat, the engine will be very slow to warm-up, and may never reach operating temperature in cool weather.

The part you are thinking of that controls the fan is the thermo-switch, an you need it as well.

 

Hmm, good to know. Thanks
I thought it's flowing all the time, didn't realize it only kicks in when a certain temp is reached. I thought this would apply to fan only.
So I should test and make sure it's actually doing that.

Thanks again. I guess I'll look into relocating the housing then and change the plumbing. Maybe I can find a smaller unit.

Oh, another question: does the size play a role? Any harm in going bigger with radiator?

 

No harm in going bigger with the rad from an operating point of view as long as you maintain the stock thermostat, or one of the same temperature rating. The limits will be the space you have available but also keep in mind that a larger rad may be more susceptible to crash damage.
If you are having a new rad made, you can have a fitting added to the "hot" side and relocate your stock thermo-switch to the rad. You would only need to do that if you were replacing your thermostat housing with an aftermarket one that doesn't have a thermo-switch fitting tapped onto it.

 

Great, thank you.
After K-moe'S explanation and reading a bit more, I now understand how it works and parts involved etc.
I never really thought about it before.

 

I was thinking about using inline thermostat housing which will go underneath the tank.


And unless I find a new radiator with built-in cap, I was thinking about adding an inline filler.


My aftermarket speedo comes with an inline temp sensor which will be added as well.
The inline thermostat housing may not have a hookup to trigger the fan, but I could always add a manual switch.

Anything I am missing, not thinking of?

 

that inline filler with the overflow has to be at the top of the system. if not, you can't fill it past the cap and the overflow will blow out water, not just steam

 

Correct.
And thermostat should have the correct temp setting +/-

 

Great. Just wanted to make sure this setup would work and my thinking was right.

If there is no automatic trigger for the fan, my aftermarket computer can be set to a certain temp to trigger an alarm on the dashboard. I could use that feasture as a reminder to turn on the fan.

Speaking of fans, how much do they actually do? And are they to blow air against the radiator (for additional cooling) or do they remove/suck away hot air?

 

The fan is a critical component if you plan on stopping the bike at traffic signals, or riding under 40 MPH, or riding on hot days, or running the engine. I had a fan fail once on a water cooled bike (relay failure). It was not a good thing. Whether the fan pushes or pulls does not matter; it just needs to move enough air through the radiator coils to let it maintain temp.

 

Thanks Moe

 

Just thought I finish this by showing what I have done. Basically changed the layout of the coolant pipes. Originally, they go up towards the front and through the frame to the radiator.
I turned everything around and routed the coolant hose along the underside of the frame through an inline thermostat into the radiator. Still waiting for one short connector to finish up. Added benefit, other than removing that massive thermostat housing, is that I freed up a lot of room to put my coils under the air box.

Here before (old pic from old engine). It's the dirty silver piping.


New setup..


Can't even be seen from side..


Inline stuff... just needs a cleanup and mounts etc.


Room for coils.. coil mounts are from a later model. Just needs to be hooked up to ground. But that's later, I ripped out the entire wiring and will wire from scratch with a motogadget m-unit (should be here this week, yay)

 

I'm concerned that the changes you made may result in the formation of an unbleedable air bubble in the head. Did you make sure that the horizontal run to the outside of the frame is above the uppemost portion of the head's water passages?

 

well, the thermostat housing is above the engine, so i should be good. unless i misunderstood?
the horizontal pipe that leads to the right is not, but from there a hose runs all the way up (to the thermostat)
i thought about it as well, but i will have to have a look again to make sure i am not missing anything

if the thermostat is closed when i refill with coolant, there will be air until the thermostat opens. but this would have been the case with the old setup as well

 

Here is a drawing. Hose runs up
Thermostat is above engine

 

OK. you're good then. I t wasn't clear if the lines running from the head went hight enough before going horizontal.
There should be a hole in the thermostat to allow a small amount of coolant to bypass the thermostat as you fill the system. You can make that part go faster by filling through the thermostat housing first, then install the thermostat and top it off.

 

Great, thanks. This was my biggest concern, thought about removing thermostat as well.
First, I will fill her up with distilled water to check for leaks. Will take a while though because I have to rewire bike first

 

Oh, it would be wise to test the welds for porosity by filling the system with water and pressure testing before filling with coolant. I'd want to leave it pressurized overnight to be sure that the water is going to stay on the inside.

 

The welds were pressure tested. I had the welds done at a radiator shop and they also tested for leaks. But yes, I'll test the entire system when I have the last part to complete the loop.

 

Nicely done. That's the same inline thermostat housing I used.