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

[chance johns]

my gauge says im over heating. it may or may not be. im pretty sure my timing is good and im pretty sure theres no airleaks.

i tested the thermostat. seems to be functioning normally. im pretty sure the pump is working fine and radiator isnt blocked.

so now im looking at the thermo switch and gauge for malfunctions.

how can i test the thermo switch? i pulled it out and it does have white corrosion/crud on the tip.
the manual online doesnt have the info for testing. it says refer to the electrical body section for info and i cant seem to find it.

how can i test the gauge?

what else should i be looking at?

ALSO the manual says inspect the wax pellet on the thermostat for cracks. mine functions as it should, but im just curious where is the wax pellet? is that the brass core? it doesnt point it out in the diagram.

i bought an infrared digital thermometer, but everybody here seems to say that they are not accurate and i wont get an accurate engine temp with it. what is the normal motor operating temp?

[GT750Battleship]

Hi,testing the gauge is easy..disconnect the temp wire from back of thermostat housing,turn key to on..touch the disconnected wire to earth..cylinder head will do,the gauge should deflect/swing to hot,if not..there is something wrong with the gauge ! Testing the thermo switch is something I can't help you with,I'm sure someone here will be able to answer that one My temp gauge usually sits just below the centre mark,or a little less.I had a thermo fail earlier this year..39c day,& the needle stayed in the blue zone, a new thermo sorted that one out
Cheers,
Roger.

[Suzukidave]

When you say the engine is running hot , how much hot ?

[Alan H]

my gauge says im over heating. it may or may not be. im pretty sure my timing is good and im pretty sure theres no airleaks.

i tested the thermostat. seems to be functioning normally. im pretty sure the pump is working fine and radiator isnt blocked.

so now im looking at the thermo switch and gauge for malfunctions.

how can i test the thermo switch? i pulled it out and it does have white corrosion/crud on the tip.
the manual online doesnt have the info for testing. it says refer to the electrical body section for info and i cant seem to find it.

how can i test the gauge?

what else should i be looking at?

ALSO the manual says inspect the wax pellet on the thermostat for cracks. mine functions as it should, but im just curious where is the wax pellet? is that the brass core? it doesnt point it out in the diagram.

i bought an infrared digital thermometer, but everybody here seems to say that they are not accurate and i wont get an accurate engine temp with it. what is the normal motor operating temp?

Points in order.
1 Is it or isn't it?
2. Pretty sure? Yes or no?
3. Why look at things if you aren't sure they are ok or not? Check connections first.
4. The thermostat switch can be tested in a pan of boiling water. Cold, it's open circuit. Hot, closed circuit. You did mean the switch that controls the fan didn't you? The transmitter that controls the temp. gauge isn't a switch, the resistance across it changes as the temperature increases and decrease so the gauge needle moves. Check as above.
5. The thermostat either works or it doesn't and usually fails open so that the engine takes for ever to warm up. Put it in the same pan of boiling water and if it opens it's OK. If it doesn't get a new one.
6. I don't know who the 'everybody' who say things are, but laser/IR temperature gauges are very accurate and can be relied on. Put the red spot on the place you want to check and read the indication. Depends where you point the dot. Hotter at the top of the engine than the bottom, shouldn't get above about 90 degrees C normally.

[chance johns]

i dont know if its running hot or not. the gauge says it is.

remind me again how to test the water pump, in the bike.

timing is on. to the best of my ability. i say that because there is always room for error, and i do what i know how to with the aid of the manual.

i havent done an airleak test in a while, but when building a bike, its something i always do, and should check again to make sure.

ive tested the thermo stat.

the fan switch shouldnt matter, apparently . everybody says the bike shouldnt need the fan to cool the radiator/coolant/motor.

where should i test the motor with the infrared? to check 90c?

the temp transmitter- where should the resistance be at what temp? how do i make sure its operating properly?
the bike doesnt seem to be running hot, doesnt act like its over heating...i just want to make sure, i love this bike and have alot of money into it. its been almost 2 years ive been trying to get this thing on the road and dont want to half ass any part of it.

i want to send it out for paint to ken at knk but im trying to be 100% with the rest of the bike before i spend the (alot) money for paint. i hate looking at the bike with a king and queen seat and flat black paint!

[Suzukidave]

You didnt say how hot its showing on the gauge ( i think ) so i am going to guess that its pegged all the way to the hot side on the gauge . A easy mistake is to attach the 2 wire connections on the back of the gauge switched , if you happen to do this the gauge will read full hot no matter what temp the engine is .

[chance johns]

ok, so the bike starts off cold. gauge reads cold. it warms up....hits the center of the gauge, then eventually reads hot. fully pegged to the hot side.

[T350guy]

Back in 78 my GT 750 did the same thing..as it turns out was a bad connection..Do the test as suggested in the above post or you will spend a lot of wasted time trying to track the issue down..

[Coyote]

Cold, it's open circuit. Hot, closed circuit.

Ah Alan, Have you been in the sauce again?

[Alan H]

Cold, it's open circuit. Hot, closed circuit.

Ah Alan, Have you been in the sauce again?

Nope. Well, not much!!

That comment is for the switch. That controls the fan and when it gets hot, the circuit closes to run the fan (or relay that runs the fan on the 750.)
He said switch, the sender for the temp gauge is a transducer (or sender unit) which usually decreases resistance as it gets hotter (that's why the gauge reads full scale when you ground the wire that goes to the sender.)

A switch is a digital device - on or off.
A transducer is an analogue device that changes a signal as a situation changes (pressure, temperature, level etc.)
Sorry to be picky, but as a commissioning engineer (I swing both ways - electrical and mechanical! - but also do process and control) - if I don't use correct terms it can sometimes cause other problems.

Can't post a wiring diagram, 'the board quota has been reached'. Looks like some spring cleaning is needed or capacity increased.

[Suzukidave]

If the 2 wire's on the back of the gauge are switched its a easy enough test to switch them to see if corrects the problem .

[Coyote]

That comment is for the switch.

I stand corrected Alan. I thought we were talking about thermostats.

[Alan H]

Keep smiling mate, I'm suffering from a lack of alcohol!!
Spending to much time in the garage, and now another 550 to start on!

[Suzukidave]

Did you switch the wires on the back of the gauge to see if it made a difference ?

[chance johns]

i heading to the shop now, but im still alittle unclear on how to test the "transducer" we have the thermostat, the fan switch, and the temp gauge transducer?

ill pull the wire and touch it to ground if the temp gauge arm pins hot it is to be assumed the gauge is good.

i'll put the transducer partially into hot water and touch the male spade end with a mutlimeter to test continuity? with what?