replace with a higher temp. thermostat on GSF400

[tomx611]

Have anyone got experience replace the original 170F thermostat to higher temper? and what's the feeling after changed that?

The factory pro recommend replace a higher temp. thermostat 190F.
CBR600F4I is a 180F thermostat
CBR600F3 180F
GSF400 is 170F
SV650 03 is 190F

since the GSF 400 fan switch turn on at 190F, seems 190F thermostat need change the fan switch.

http://www.factorypro.com/prod_pages/prods41.html

Refer from above link-
SCHMIGGY6@aol.com wrote:

I HAVE TWO QUESTIONS:
FIRST, I HAVE A 94 RF900R WITH A V&H SS2R SLIP-ON AND A K&N FILTER, AS WELL AS A STAGE I KIT. THE BIKE RUNS GREAT AND I WANT TO KNOW IF AN IGNITION ADVANCE WOULD DO ME ANY GOOD (WHAT WILL ONE DO?) ALSO DO YOU HAVE ANY DYNO
INFO ON A RF900?
SECOND, MY GIRLFRIEND HAS A 93 BANDIT 400 THAT HAS ALWAYS HAD POOR CARBURETION. WE ARE CONSIDERING A STAGE I KIT AND POSSIBLY A NEW PIPE/FILTER/ADVANCE COMBINATION AS WELL. DO YOU HAVE ANY DYNO INFO ON THIS BIKE AND HAS IT BEEN YOUR EXPERIENCE THAT THESE MACHINES HAVE SUCH POOR JETTING FROM THE FACTORY?
THANKS , AND GREAT WEB SITE!!!!!!!!!!
SCHMIGGY6@AOL.COM


The 400 Bandit?

Part of the problem is, like ALL of the 93-95ish watercooled Suzuki's, that it's got a very low temperature coolant thermostat ~170f, or so. Makes them seem to run lean and not idle well when the fuel screws are set for best idle after a good ride. Install a higher temp thermostat from, perhaps a cbr600f3. We use ~190f  thermostat, which is a bit higher than the f3, but 190f is where the engine runs the best and makes the best power. Either way, changing the thermostat is mandatory. Then you can tune the carbs for best throttle response with the kit.

It won't make the bike run too hot, it will just keep it from running too cool when just cruising around - like summer in foggy San Francisco - that is, south of the Golden Gate Bridge cause it's warmer to the north.

The CRB-S41-1.0 Carb Recal Kit will work much better - cleaner and more responsive everywhere. There is no ignition advance available.

If you were close to us, I would like to do a 1.7 style kit on the 400.

[Chris H]

I put a CBRf3 one in mine years ago and ive not noticed any BUT i did a load of other stuff at the same time.

[T2098]

I was looking for information on thermostats to buy for my Bandit 400, and just wanted to clear up one little misconception in this thread:

The OEM radiator fan thermo-switch doesn't switch the fan on until ~95c (203F) as per the USA factory service manual.  It does have some hysteresis, and it doesn't shut the radiator fan off until the coolant temp drops back down to 88C (190.4F), but it still shouldn't actually turn the rad fan on unless the bike is actually getting warm, even with the hotter thermostats.

The Japanese factory manual that I have actually specifies a fan thermoswitch turn-on temperature of 95-101C (203-214F) and a turn-off temperature of 88-94C (190-201F)  Even if the switch is in the middle of the manufacturing range, this should provide enough margin for it to operate properly with a 195F t-stat.

It remains to be seen whether it'll get cool enough to switch the fan *off* after it's been turned on with the typically used 195F Stant automotive replacement thermostats, but I'm going to try it anyway.   Will report back when I have more conclusive info. :)

[Chris H]

Its not about the fan switching or the temp at which the fan switches back off,
Its actual thermostat its self, in the late 80's early 90's suzuki used thermostats that opened at a relatively low temp, using a slightly higher one helps idle and pick up, its been well documented for loads of different models.
So your base temp for the bike is slightly higher.

[greg737]

Chris H, the voice of reason...

He's right, the thermostat affects the LOW END of the system's operating range not the upper end.  The upper end of the temperature range is determined by the actual design (the architecture) of the cooling system - things like: How big is the radiator compared to the engine, how much surface area does the radiator have, how much fluid does the water pump move per minute and how large are the hoses to and from the radiator.

[T2098]

Chris - I understand the function of the thermostat - the problem is that if the thermostat temperature is too high relative to the radiator fan thermoswitch, you could get into a situation (and the Bandit looks to be very close) where the radiator fan thermoswitch shutoff temperature is below the thermostat opening temperature.   

If this is the case, as soon as your rad fan turns on once, it'll stay on until you switch the bike off due to the hysteresis.  Not the end of the world, but just means that going down the highway on a cool day, your radiator fan will likely run constantly.

[T2098]

Thankfully, after some testing, it looks like everything works the way it should, although just barely. :)

The 195f thermostat definitely keeps the coolant very close to the rad fan thermoswitch's turn-off temperature, but it does still cycle the fan on and off.

[OldSchlPunk]

Haven't been on here in a long time...

I'm using a Stant 13849 in my bike. It's rated @ 195* and doesn't cause problems with the fan. I believe this number crosses to a GM 4 cyl.

With this thermostat, the bike runs great. Gone is the cold-blooded nature.

[greg737]

There's another step that can be taken to refine the GSF400's cooling system.

If you look at the cooling system plumbing for most every modern motorcycle you'll see that there's a small direct-to-the-water-pump return line.  Modern cars all have this also.  It allows for a small amount of coolant to continuously circulate through the engine before the thermostat reaches its opening temperature. 

This coolant system design is good for the engine because it evens out the temperature gradient throughout the engine's mass.  This prevents/reduces wear inside the cylinder barrels.

Here's an example of the 1999 Suzuki SV system. http://www.partzilla.com/parts/search/Suzuki/Motorcycle/1999/SV650/RADIATOR+HOSE/parts.html

In this SV650 parts diagram item number 24 is the direct return line.  You'll see that it leaves the thermostat housing prior to the thermostat and, as its name implies, it leads directly back to the bike's water pump.

The thing that makes installing a direct return bypass line easy on a GSF400 is that the B4's thermostat housing already has an extra port available (sticking right out of the bottom of the housing).  This extra port is there because the GSX-R400 used the same thermostat housing and that bike has three temperature sensors.  The B4 only has two temperature sensors so when Suzuki built the B4 they didn't drill out the casting for the third sensor.

I installed a direct return line from this extra port to the radiator return line that leads into the bike's water pump.

That modification plus installing a 195 degree thermostat brings the B4's cooling system up to modern day spec.

[bdouvill]

Hi there,

I wish I have Greg's skills to modify the thermostat housing and create a return line but I don't :-(

What I did is to take the advantage of yearly maintenance back in September to replace the water hoses with brand new silicone ones. Then at the same time, I digged the internet to find a proper replacement for the thermostat. Answer came from here:
http://www.400greybike.com/forum/viewtopic.php?f=53&t=50878

So I ordered this 17670-06G50 from Suzuki which is a direct fit inside the original B400 thermostat housing. Opens at 88 degrees C instead of 73-78 for the original. Engine definitely gets hot faster which is good. I believe the only drawback is that 88 deg C is now closer from the radiator start temperature (117 deg C according to the manual). So I noticed that radiator starts more often, especially when I get caught in traffic jams after I ran for like 10 to 15 minutes max.

All in all, I am pretty happy with this super easy mod (as long as your cooling system is already in pieces).