On liquid cooled engines By borris120 (Read 884 times)

[borris120]

I am not sure what temperature your engines run after warm-up, mine sits somewhere between the bottom 1/4 and C at idle, and between 1/4 and 1/2 after WOT on a hot day.
On a cold day, such as the past two evenings here in SLC, it has been sitting a hair above the C mark even after WOT for almost an half hour. Outside temp was probably low 70's high 60's.
I would like to ride this bike on into the winter until I am contending with ice, however this won't be possible if the engine wont stay at an optimum temperature for combustion.
I don't think the thermostat is having issues opening, I believe that to be the issue.
Is anyone aware if you can order hotter thermostats like you can for automobile engines?
Otherwise, and possibly still, I will have to wire a switch in to the radiator fan circuit.
suggestions?

borris

[novaraptor]

While I don't know if you can get differing temperature thermostats,
there are a few things to consider. If the temperature gauge is like most of the other chino gauges, then you cant really know for sure how accurate the gauge is. I'm presuming that this is your first coming winter with the scooter. I would see how well it works as the temperature drops. A quick and easy way to increase the temperature if there is a problem would be to cut small cardboard slats to decrease the airflow through the radiator. Do you know if your fan comes on? If the system is always cold, putting a switch in the fan circuit won't matter, cause you wont be turning it on anyway. If the fan is coming on now, and your gauge reads as you have said, then the gauge is wrong. It should be turning on when you are above the half way mark. hope that's some help.

[borris120]

So, I've had it up to the 1/2 mark on a hot day after being on a highway. Generally it gets up to 1/4 and then the fan will kick on if it is up on the stand. If I am driving, the fan is always on. In fact, when I turn the ignition, the fan is on. I was thinking of getting a cutoff switch, but knowing myself, I wouldnt turn it back on until the engine has seized. Was thinking of getting a different thermo-gauge, and/or getting a different thermostat for the fan. I don't mind doing some custom work as I am looking at putting in an EGT sensor and gauge. I really want to get max efficiency as both a prior hyper miler and pilot. Barometric pressure can play a hefty role in the function of a carbureted engine, and we can see 2" of change in a day here, over 3" in a week. I just figured I would put in an EGT and remote the mixture screw.
Either way, I had the cardboard as a reserve idea once our harsh winters arrive, but until then I need a solution because the engine will only want to idle unassisted once it is sitting at 1/8 on the temp gauge.

Boris

[kz1000st]

My two cents is this. If the fan is kicking on when the gauge reads 1/4, I wouldn't trust the gauge. A thermoswitch operates the fan and usually only switches on the fan at the point it's starting to get warm. I would stick a meat thermometer in the radiator to see what it is.

[borris120]

Are you saying that the fan shouldnt be on when I turn the key? As I said before there seems to be a switch on the stand, because when I start the engine the fan is on. If I then put the bike up on the stand, the fan will cut off. Once it gets warm, the fan will come on and off intermittently.
I wonder if I can get another gauge for coolant temperature? Or possibly it is the sensor? I might just replace the whole getup.

Boris

[novaraptor]

Lots of people have found the fan being hardwired to run all the time. If it comes on when the key turns on then that is the first thing to fix. If you check the wiring at the radiator it is usually not even connected, just wired together.

[novaraptor]

The fact that the fan isn't on when the scoot is on the center stand makes me think that there may be a pinched wire. Normal ops is that the fan is off until the temp sensor in the radiator gets to around 190 or so. The sensor causes a closed circuit and the fan starts and runs till the temp drops. Any other fan operation is abnormal, either because the sensor is bad, has been removed from the circuit, or because there is a break or ground in the wiring.

[borris120]

Well when I put it up on the stand, and the engine is cold, the fan will shut off. Then it will kick on just above 1/4 for a minute or so until the needle drops, then back on again once it gets just above 1/4. It has been pretty reliable in that respect. Possibly there is a ground when it is off of the stand, completing the circuit, and keeping the fan on all of the time? I will have to take a peek tomorrow. On which side is the thermo switch located?
I appreciate the help,

Boris

[novaraptor]

on the mc-79 its on the lower left, as you sit on the bike. I would guess that most of the radiators on the 250's are sourced from the same factory, so it should be there.