GT750J over heating.....or is...it?

[chance johns]

gauge is good. thermostat is good.

how do i definitely test the water pump and temp-transducer?

i will give another airleak test.

whats the hottest the motor should get ? if imm using my infrared gauge,where should i direct the beam?

[tz375]

Test the top of the radiator and bottom, across the head and the barrels plus the thermostat housing (above and below) when it's showing hot on the gauge.

Do you have a fan on yours and if so does it switch on? If not either it's broken or else it's not as hot as it looks. Is the system full of water/anti freeze? If there's an air pocket that could create a false reading.

Have you flushed the radiator recently?

[Alan H]

Have you got anti freeze in the coolant?
Just water will fur up all the internal galleries and cause problems with the thermostat and other parts.

[chance johns]

i was having an issue with the fan. but i read that the fan is arbitrary. ok. so i'll test those spots with my infrared, but what does it need to say? IS IT THAT OBVIOUS, AND I JUST DONT GET IT?

[pull the wire]

I tested my temp gauge sensor, and at ambient temp here in Phoenix (80 degrees F) and it ohmed out at 470 ohms. I then heated it up with my propane torch quickly and the resistance at the temp gauge sensor decreased. My temp gun is at work so I'm not sure of the actual temp I heated the sensor to. The resistance definitely decreases as the sensor gets hotter. The temp gauge moves by varying the 12volts to ground. The more resistance (cooler temps) the lower the gauge reads. As the temp increases, resistance decreases providing more voltage to the gauge and represents higher temp reading on the gauge.

Hope this helps

[yeadon_m]

On my 750A radiator, after a good long run, the IR thermometer indicated 80C at the top and 70C at the bottom.

I can't find my records on what temp was indicated on the hottest spots just above the exhaust manifolds on this bike, but on my GT550B, these range 105-110C measured on small,matt black spots I've painted on the pots!

Hope useful,
Mike

[chance johns]

I decided to buy a cheap dig gauge to hook up to my temp sensor to see if i am actually over heating. my plan was to get it to operating temperature, see what the gauge says, and cross reference that to my thermo laser, for accuracy. Once i determined it was functioning i would take it out for a test and see if i could get it to climb past 100c (212f).

the gauge is an automobile gauge. it has leads for ground,hot(keyed),and sensor. it comes with a sensor but i assumed it would not be the same diameter/thread pitch as the old one so I'm using the old one. which I'm pretty sure I've tested before. i am also assuming the resistance ratings are pretty universal for temp sensors/gauges.

ok so the leads on the gauge are a very small diameter. much smaller than em wires on the gt(18g?) and they are too short to stretch from my mounting application.they are meant to mount into a dash. so i take some new wire i have(18g?) and extend it. i twist the wires and electrical tape it. i do the same with all the leads except for the hot i put a bullet connector in line so i dont have to cut into a keyed hot and can disconnect manually. i was gonna do a switch but whatever. this is temporary and for testing purposes. i had to use the larger gauge wire because i dont have connectors that small.

i wire it up and it says 60. i dont know if its celsius or fahrenheit but in the instructions, wen it talks about temp it only seems to mention c, so i assume its c.
my garage was probably 80 degrees and some change. i imagine the coolant was the same. the outside of the motor was thermo layered at 80 something.

did i gain resistance by changing to a larger gauge wire? is the resistance ratings incompatible amongst different gauges/sensors? is my sensor bad,in fact?

I'm really trying to make this happen and keep getting stumped. THERES A CLASSIC 2 STROKE show in a week and I've been telling myself for years now THIS IS THE YEAR I BRING MY BUFFALO AND ENTER IT FOR SHOW.

[Coyote]

i would take it out for a test and see if i could get it to climb past 100c (212f).

I have never know a buffalo to reach boiling temperature. That's why Suzuki ditched the fan. These bikes were slightly over cooled and consequently were slow to bring to operating temperature of 180-185.. On most rides in fairly cool weather the thermostat never even opens.
p.s. I only owned one. A 77B model, but I have read a lot. Mine always ran just below middle on the gauge. I do know if you get the wires to the gauge reversed, it will be hot when you key on, but that's probably already been covered.

[chance johns]

how were you aware of the specific temperature alan?

when my gauge was almost at the third line just before H the top of the cylinder head read 139f, just above my exhaust header on the cylinder read 204, top of the radiator read 205f, and bottom of the radiator read 149.

[yeadon_m]

If you pull the bullet connector from the temp sender and touch it to earth, with the ignition on, the temp gauge should slowly swing over to max. If you then take it off earth, the meter should slowly swing back to zero.
If it does these things, your meter is probably OK.
If you measure the resistance from the isolated bullet stub on the temp sender, to earth, when the engine is cold and as it warms up (do this intermittently so you can review the temp gauge readings) it will show decreasing resistance as it heats up.
On my GT750A, I got the following, readings:
Cold: 685ohms. Needle on blue mark: 130ohms. Needle on lowest white mark: 89ohms. Needle midway between lower two white marks: 70ohms (top hose still cold/cool, T’stat closed). Needle on centre: 52ohms, just as T’stat opened and top hose / rad heated up quickly. Needle one needle-width to left of centre as cold water circulated: 57ohms.
If your readings are in the same region, I'd say your sender is OK too.
In that case, if your temp gauge is reading well above the centre, certainly over halfway between centre and max, it is overheating and you should dig in on why.
On many gauges, there are two faint dots, one to the left and one to the right of the centre line. They're not obvious but often there is you look for them. These are Suzuki's lower and upper 'normal' limits, which are quite wide.
Cheers,
Mike

[chance johns]

wow. thats useful info. ill check that out. also if theres corrosion on the bullet connector that can add resistance to the reading to the gauge.
I've read that gauge test before and it seems pretty basic. mine does what is described.

[tz375]

Mike,
That was really useful data. Thanks.

Chance,
Once you finish your testing and have decided if it's the sensor or the gauge or the fool bike really is running hot, what next?

Sounds like it's time to flush the radiator out, check timing and plugs and see why it's hot.

[yeadon_m]

Richard,
Thanks
I am sometimes obsessive, but here it was sheer interest as I'd never considered how these temp gauge systems work.
By the way, it follows that, if anyone wants to, they can set their temp gauge to read wherever they want it to when hot, provided its a lower reading than the stock sensor provides. The means is to install a discrete, in-line resistor of a few (low, single figure) ohms, and it will raise the hot resistance of the circuit a hair, so the needle sits where you choose. I've done so, set now just a needle under centre. Kidology of course - the temp is what it is.
Cheers,
Mike

[chance johns]

so currently im trying to test the resistance of the sensor and my meter is just cycling through low and high numbers and OL with the key on. not running. i have a wire with an aligator clip attatched to the red lead on my meter and the other end is a small O connector with the female bullet connector on as well.

im looking up how to test my sensor(sending unit?) again, to be sure. also found great info on this subject here---->http://www.kettleclinic.co.uk/kcforum/v ... 1&start=10

still trying to figure this out tho! thanks!

[chance johns]

i was getting ready to test my coolant system with the thermo laser by aiming it at one the rusted head bolts. it should read 124f at the first line according to the kettle clinik thread. and i dropped it and the laser broke so now i dont know where im aiming it. also i saw the two dots that should be within operating temperature and i was cutting the bike off at the second dot thinking it was too hot. i was not aware of the dots previously.