Running Temp

[Gixxer 4 ever]

Two weeks ago I went from Napier to Taupo and back. I left Napier at 8.30 and it was cold. The bike ran well but.......From the Mohaka bridge on, there was a lot of ice and the air temp was very cold. The bike temp gauge dropped to 48 beg in the hills. When I got to the long plains it dropped to 42 deg. Now it was a very cold morning and the road was frozen solid. It took one and a half hours to go from Napier to Taupo. I could go on for ever about the ride but my question is... Could it have been so cold that the engine case and radiator etc lost so much heat that it could not retain a normal operating temp or would the Thermostat be allowing water to circulate through the radiator and not allowing the temp to build up? As soon as I got to the turn in to Taupo the temp returned to 57. No problems on the trip home or since. This is a 1997 GSX-R 750V

[merv]

Sounds like your thermostat needs replacing because they should hold the engine temp at or above the temp the thermostat opens at - i.e. if the air gets colder it should close down and prevent so much water circulation to the radiator.

As a comparo, my wife's Honda car did this last year and she hadn't noticed - I drove it one night and thought jeez the temp gauge damn near dropped to zip as we headed down the Nguaranga Gorge. Other problem was it meant the engine wasn't warming up as quick and the fuel injection was forever compensating by pouring in more fuel. One new thermostat and all fixed - it warms up quick and stays at that temperature.

It is not good for a motor to run too cold.

[MikeL]

Can't speak from recent experience but in the past I have found thermostats to be a bit unreliable. Once they get a bit old they tend to stick in the open position (better than staying closed, I suppose).
Having said that, I have found that on my Honda where I'm pretty certain the thermostat is working properly the temperature on the open road in winter is always well below the half-way mark. But 57 deg seems very low for "normal"...

[DEATH_INC.]

My 'X' normally runs 77deg,so 57 seems awfully low,and yeah,I'd look at the thermostat.

[scumdog]

My 'X' normally runs 77deg,so 57 seems awfully low,and yeah,I'd look at the thermostat.

Especially when most water cooled vehicles run at 80 -90 degrees

[Kickaha]

My 'X' normally runs 77deg,so 57 seems awfully low,and yeah,I'd look at the thermostat.

Would that not depend on where the sender unit is and where it's being measured from?

With the TZ250 superkart we go for 55deg measured at the top of the radiator,or do two strokes like a different temp range than the four strokes?

[merv]

Would that not depend on where the sender unit is and where it's being measured from?

With the TZ250 superkart we go for 55deg measured at the top of the radiator,or do two strokes like a different temp range than the four strokes?

Yeah 2 strokes seem to be cooler where they measure it as per our discussions about Mr Melon's bike a few months back.

4 Strokes tend to have the sender near the thermostat on the cylinder head and typically 80+ is the temp. Basically to know the answer to what it should be you need to check your manual if you have one as to what temp the thermostat should open at as thermostats are sold as say an 82 deg or whatever. The radiator cap then has a specified pressure rating as well which allows the engine to go above normal boiling point typically 10 - 20 deg more than 100 when working hard without losing water.

[Motu]

42deg sounds totaly wrong,I don't think a motor would even run at those temps - even with the thermostat removed most motors will get up to 80deg under normal running.Where is the sender unit located?

[jimbo600]

My 'X' normally runs 77deg,so 57 seems awfully low,and yeah,I'd look at the thermostat.

The new K3 750 runs at 76degrees. So 57 is way too low mate. However, as I know fuck all about mechanics I can offer no solution, so I'll go with Death on this one, it must be the thermostat.

[Gixxer 4 ever]

42deg sounds totaly wrong,I don't think a motor would even run at those temps - even with the thermostat removed most motors will get up to 80deg under normal running.Where is the sender unit located?

It ran at that ok but as we all know it is way to cold. Found the problem see message below.

[Gixxer 4 ever]

Would that not depend on where the sender unit is and where it's being measured from?

With the TZ250 superkart we go for 55deg measured at the top of the radiator,or do two strokes like a different temp range than the four strokes?

Yes and it is in the back of the thermostat case. That is attached to the back of the head. Problem solved see note later in this thread.

[Gixxer 4 ever]

Pulled the thermostat out yesterday to find some one has gutted it. Left the frame in to seal the cap when screwed back on. SO have replaced it. Many thanks for the feed back. It is good to know what other bikes run at. I am a touch worried as to why the previous owner removed it in such a fashion. I note the temp stamped on the old one and the new one is 76.5. So I am happy to get that sorted. Lets see what happens in the summer. Thanks people for your help.

[merv]

The dork probably thought he was gonna make it go better contrary to what really happens. The real guts with keeping an engine from getting too hot is the size of the radiator, air flow across it and the pump capacity and the electric fan. Once the engine reaches the temp of the thermostat anything above that the thermostat has no effect so it won't help overheating to put a cooler thermostat in or to have it jammed open or holes cut in it or whatever. However on the cool side is where they control as they act like a regulator to control the amount of water that flows to the radiator.

What you said Motu about normal running, the example I gave of our Honda car they won't hold temp if you are running downhill on a cold night, the radiator capacity is just too great for that and it overcools the engine badly if the thermostat is stuck open.

[Kwaka-Kid]

just to give another reference my VFR400 runs @ 85degrees on m/way @ 100kmph and generally everywhere, all rides i go on, unless it gets tight and twisty and im ringing her balls (then she goes to 90degrees).. or sitting in traffic/thru auck city she runs up passed 90degrees (say, 95, even up to around 100 - this is apparently normal for a viffer)
So yeah, only on VERY cold mornings going to work does my bike sit @ like 70 degrees - so i just dont revv her hard etc, take it easy/

[Motu]

Over run down hill cools a motor down real fast alright Merv - on an engine transplant I did years ago I didn't fit a thermostat as I wasn't too sure about how it would go,I had a super acurate Smiths capilary tube gauge on it.I could see a temp drop as I went past the shade of some trees - on a down hill you could just watch the gauge unwind like the second hand of a watch in reverse.