Water pump

elbert · Post by **elbert** » Thu Oct 08, 2009 2:59 pm

Is it an easy way to check the water pump on a GT750? My temp gauge stays at the red area and changing the thermostat didn't fix it. I suspect the temp sensor since the engine doesn't seem to be that hot, but thought I should check the water pump before ordering any parts.

tz375 · Post by **tz375** » Thu Oct 08, 2009 3:43 pm

The first rule is to check the gauge first.

The best way to check the waterpump is to temporarily fit another temperature pickup and a digital temperature gauge to see what the temperature really is.

There isn't much to go wrong with the pump. Seals may fail, but teh pump typically doesn't wear out.

Is it possible that the radiator needs to be back flushed top clean it out or do teh fins on the radiator need to be cleaned?

Suzukidave · Post by **Suzukidave** » Thu Oct 08, 2009 4:30 pm

Is it possible that the 2 wires on the gauge got swapped as this will always make it full hot .

Coyote · Post by **Coyote** » Thu Oct 08, 2009 4:38 pm

If it goes to red right after you start it, the wires inside the temp gage are reversed. If it takes a while to go red, then it's something else. If the engine doesn't feel hot then it probably isn't. 750's run cool by nature. On my 77B the temp gage never passed the middle even in 100+ degree weather. I had the radiator boiled out at an automotive shop while doing the build on mine. Still had the original 77 thermostat in it.
You are getting a false reading it seems. You might try to borrow a temp gage from someone here or do as tz supggested -- different sender and a digital gage.
Does the radiator get hot? If everythig is working correctly, it should get quite warm. Is your thermostat right side up?
Just my 2 cents.

Post by **Suzsmokeyallan** » Thu Oct 08, 2009 4:49 pm

Guys those are all good tips, something ive noticed on the radiators i cleaned and restored is that they had various levels of crusty flakes in them.
It looked like in the past some POs used plain water for a long time in that particular bike.
To clean them i used some lime away in them sitting for awhile and that loosened the scale up significantly. HOWEVER after i dried them out and left them for a few weeks i noticed more scale peeling up on the surface inside so i redid them again and more came out, but this time the results were super clean.
On a bike you have owned after a string of POs its best to clean the radiator first and then test the operating temperature by a thermometer.
Also, it cant hurt to remove the hoses and check all the passages into the cases and from the large drain bolt.
You'd be surprised what you can find, from large stray blobs of silicone to bits and pieces of gasket and even pieces of old hose blocking the tubing.
Another good idea is to add some vinegar to distilled water and run it through the system at least once every two years.
For this you would drain the old coolant, add the vinegar/water mix, run the bike till it reaches operating temp, then dump it and flush with distilled water.
After it drains out completely add new coolant and go riding.
If you want to verify the pumps at least working, a simple look down into the filler neck, you should see the coolant moving across it when you rev the engine.

elbert · Post by **elbert** » Thu Oct 08, 2009 11:29 pm

It's not the wires as it takes some time for it to reach the red area.
The radiator gets hot, but not worse than I can touch it, the cyllinders get hotter, but I can touch them for a few seconds without any problems.
When I replaced the thermostat I drained the coolant and it was very clean.
I've tried to look down the filler neck, allthough I can see movement of the water it's not much and I thought it was only the vibrations that caused it.

I think I'll try to get a new sensor and see if it helps, I'll have plenty of time to fix it since riding season is at it's very end here...

Post by **Suzsmokeyallan** » Fri Oct 09, 2009 7:44 am

You could also get a thermometer and verify the operating temperature is within spec. Even of the coolant is clean that doesnt mean the radiator and internals are clean, remember scale doesnt float around it sticks to the surface its adhered to originally.
A new sensor to replace yours is a good idea if you do not know how old it is.

tz375 · Post by **tz375** » Fri Oct 09, 2009 11:59 am

Radiators do get clogged over time and need to be cleaned out, but the place to start is the gauge and sender.

I suggested a different gauge and sender to use as a cross reference to determine if there is a problem.

Another approach is to swap out the sender and then the gauge and see which one fixes the problem. With a replacement gauge, just connect battery 12v to one side of the new gauge and connect the other side to the terminal on the sender. No need to replace it in the cluster unless/until it shows that it's incorrect.

When the motor is nice and warm, swap the connection to the sender from the stock loom to your new gauge and you'll see them back to back.

If both read high, swap out the sender and see if that fixes it.

rngdng · Post by **rngdng** » Mon Oct 12, 2009 7:05 pm

Suzukidave wrote:Is it possible that the 2 wires on the gauge got swapped as this will always make it full hot .

Been there, done that. Reverse the wires on the gauge.

Lane