New to me gt750a

[canaletto5]

Run it without the thermostat. It will prove whether it's working or not. Kev

[stupot]

Hi salmans eight.
Ive just been reading your posts , wow youve done alot lol. with regards to the coolant temp and pressure. When running right these bikes over cool as the rad is super efficient.
In your case it sounds like your looosing pressure and if youve no leaks and your coolant is at the correct level a new rad cap might be helpfull.
to answer your question this is how ive managed in the past.
Flow can be observed with the bypass hose disconnected under the head on the right and a short blip with plugs out on the starter button will force a small amount of coolant out for a brief moment and then it will return as the pressures equalize.
Its not a water pump it just makes it go in the right direction if theres a block it will not flow.

[Salmanz8]

Thanks guys, plot thickens.
I was really hoping that i have a bad sender unit, so snagged up a nos one. The compare almost identical, both hot and cold.

Thermostat is maybe a touch slow to open, but i am really being picky here. Both opens and closes.
BTW where do you source a replacement thermostat since i already have it out ? Worth replacing a 50 yr old stat ?
Also, where to find a replacement rad cap ? Havnt tested mine yet, as i got a little tied up due to some health concerns.

But any how, will shortly be getting back to things, as it is all apart at the moment.
I did see some hoses at hvc, but thinking about replacing clamps as well, are they still available from suzuki ?

[Salmanz8]

Run it without the thermostat. It will prove whether it's working or not. Kev

Might just do that.
I am gona clean the thermostat again, retest, and put it alltogether, if that doesnt then out with the thermostat and retest

[Salmanz8]

So here is a bit of update.

NOS thermostat
NOS thermostat gasket
NEw genuine suzuki hose and clamps
NOS coolant temp sensor

Honda TYPE 2 coolant

Radiator cap is not replaced.

I can see that the thermostat does open, i can feel the radiator going warm and staying warm.

I havnt ridden the bike, but i did let it idle, and the temp needle goes past half mark still after about 15 mins of idle time

I stuck an oring in the filler neck, to possible seal the cap if there is a leak.
Is this how its supposed to behave at idle ? Does it need to be moving to regulate temperature ?

When i do push the red pressure release button, i dont hear any pressure being relieved. Which is odd.

I will go ahead and replace the cap too, not sure why i didnt order it with everything else.

Is there anything i am missing ?
I didnt see any air burps in the fluid either.

[Salmanz8]

Is there a resistance/temp chart to measure the signal from the sensor ? Since i do not have a spare temp meter.
The engine is running good, carbs are synced, starts up after months of sitting immediately, i am somewhat dead ended here.
Sure, i can replace the rad cap, but i am not sure yet.

[teazer]

Remove the sender and replace it with an adapter and new sender (probably be 10mm thread) and fit a temporary aftermarket temp gauge from Daytona or anywhere else and see how hot it actually gets. Of course we have no idea what "normal" on the OEM gauge is supposed to represent in terms of temperature, but if it's less than say 200f when running hard or in traffic on a hot day, it's fine.

The 'stat opens at 90c or so IIRC. Check the FSM for the right numbers. I think it states opening temps and also quotes resistance values for the sender IIRC.

Remember what they taught pilots in WW2: If a gauge reads that there's a problem but the thing is still flying and feels fine, it's probably a bad gauge. Same applies to bikes.

My street GT750 came back from one run at the drag strip and the spiffy electronic gauges told me I had reached 232MPH at over 11,000 RPM. Clearly the gauges were telling porkies. I suspect that yours is too.

[Salmanz8]

Remove the sender and replace it with an adapter and new sender (probably be 10mm thread) and fit a temporary aftermarket temp gauge from Daytona or anywhere else and see how hot it actually gets. Of course we have no idea what "normal" on the OEM gauge is supposed to represent in terms of temperature, but if it's less than say 200f when running hard or in traffic on a hot day, it's fine.

The 'stat opens at 90c or so IIRC. Check the FSM for the right numbers. I think it states opening temps and also quotes resistance values for the sender IIRC.

Remember what they taught pilots in WW2: If a gauge reads that there's a problem but the thing is still flying and feels fine, it's probably a bad gauge. Same applies to bikes.

My street GT750 came back from one run at the drag strip and the spiffy electronic gauges told me I had reached 232MPH at over 11,000 RPM. Clearly the gauges were telling porkies. I suspect that yours is too.

I could find any sender info in the fsm, but i think, that may be i was just expecting too much from the cooling system. Considering there is no fan, i guess a road test has to be in order.
If it stays cool while moving, i think we are good then.

Last night i rode a mile or two in my parking lot at work.
Temp was around 24 degree Celsius, and i could tell that it would cool down a bit if it started moving.

I though of doing the exact same thing, sticking a digital temp guage.

[teazer]

72 FSM says thermostat starts to open at 82c (180f) and fully open at 95c (198f) so they expect water temps close to boiling and that is why the cap is pressurized, to raise the boiling point. They even have a chart there that says at 6psi, boiling point is 110 (230) so it's not like the 60c numbers we read for race TZ Yamahas. They are supposed to be hot.

I couldn't find a spec for the sender, but the batch I have here tested at notionally 550ohms. One was as low as 500 and the highest was 575ohms.

Edit: at boiling in a pan, resistance was 77-80 ohms on all of the ones I tested.

You could test yours for comparison but it's likely to the the gauge out of whack.

Just as a point of reference, many modern bikes with fans and all sorts of fancy electronic contols, tend to get really hot in traffic and it's not unheard of for Ducati's to overheat. I still think yours is most likely the gauge though. It would be good if someone could actually test those temperature gauges ad calibrate them with a variable resistance. Maybe someone can do that.

[Salmanz8]

72 FSM says thermostat starts to open at 82c (180f) and fully open at 95c (198f) so they expect water temps close to boiling and that is why the cap is pressurized, to raise the boiling point. They even have a chart there that says at 6psi, boiling point is 110 (230) so it's not like the 60c numbers we read for race TZ Yamahas. They are supposed to be hot.

I couldn't find a spec for the sender, but the batch I have here tested at notionally 550ohms. One was as low as 500 and the highest was 575ohms.

Edit: at boiling in a pan, resistance was 77-80 ohms on all of the ones I tested.

You could test yours for comparison but it's likely to the the gauge out of whack.

Just as a point of reference, many modern bikes with fans and all sorts of fancy electronic contols, tend to get really hot in traffic and it's not unheard of for Ducati's to overheat. I still think yours is most likely the gauge though. It would be good if someone could actually test those temperature gauges ad calibrate them with a variable resistance. Maybe someone can do that.

I second that. Yesterday again, a bit cooler night, i rode it out in the parking lot, maybe 3 miles this time in first and second gear.
Seemed to be cooling as it was moving.
I will only know for sure only when i test ride it.
But i am suspecting, that may be i am looking for a solution to a problem that may not exist. Without the fan, there would be eventual rise in temp standing still. May be i am expecting too much from the cooling system.