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Rode today about 150 miles.. in higher temps.. and she did OK. Maybe not Great, but OK. One step at a time...
Will change oil after heavy Yamaha RingFree dose.. then order more parts (water pp mech seal, o-rings, shaft, etc)..

Need to change focus before getting 'burned out' with lack of total success..

Full Narrative Here....

Here to help if I can Don. Just going to throw out some logic for consideration.
The engine thermostat measures and reacts to engine temperature and no matter what the ambient temperature does not react to ambient temperature so whatever you're witnessing on the temp gauge is what's happening in the engine.
When the thermostat opens and exchanges coolant between the rad and the engine, the coolant headed to the rad is around 180 F and the ambient temperature around 80 F. That differential, the greater it is the quicker the exchange of heat but in theory even if it was 140 F outside, there would still be a transfer of heat and unless the creation of heat is greater than the expulsion of heat, the thermostat should be able to maintain the engine temp at operating temp.
In the 50 years of wrenching I don't think I've had to change out more than 3 thermostats but in every case where I did, that was the problem. I still think that for whatever reason, you're experiencing a bad thermostat, be it a weak thermostat or a misfitting thermostat due to some dimensional issue.

The only other thing that comes to mind and don't hold me to this is I have it in the back of my mind that the fuel gauge and thermostat work at a reduced voltage from system voltage due to the indicator needle gauges. I'm hoping that I'm not having a senior's moment but I also have it in the back of my mind that Scotch came across this some time ago. That being said, are we sure that the indicated temp is accurate? or are you chasing a ghost?

I haven't had cooling issues but I temporarily fitted a cheap digital temperature indicator as a cross check. They are cheap but accurate enough for this purpose. Lots on fleabay. They have internal battery so no wiring needed.
Here's the item number of the one I got. 274386235926. Beware some similar looking only go to 70 deg c.

Most i ever saw was 89 deg c in traffic but usually about 86 at mach 1.
Note... mine is a UK ZG1300 DFI.


I used a blob of silicone sealant to attach the sensor to the coolant outlet, then added a piece of insulation about 2 x 2 inches to prevent any false reading due to air cooling.

Stiggy wrote:

I haven't had cooling issues but I temporarily fitted a cheap digital temperature indicator as a cross check. They are cheap but accurate enough for this purpose. Lots of fleabay. They have internal battery so no wiring needed.
Here's the item number of the one I got. 274386235926. Beware some similar looking only go to 70 deg c.

Most i ever saw was 89 deg c in traffic but usually about 86 at mach 1.
Note... mine is a UK ZG1300 DFI.

I used a blob of silicone sealant to attach the sensor to the coolant outlet, then added a piece of insulation about 2 x 2 inches to prevent any false reading due to air cooling.

I have an Acewell aftermarket speedo / tacho unit on my ZG, the coolant temp sensor scews into the same place as the original temp gauge sender, the display is in degrees C, I get pretty much the same readings. The fan comes on at 87.

Stiggy wrote:

I used a blob of silicone sealant to attach the sensor to the coolant outlet, then added a piece of insulation about 2 x 2 inches to prevent any false reading due to air cooling

Are you just attaching it to outside of aluminium housing or hose or somehow into coolant liquid?

Just to the outside... hence the insulation to prevent air cooling of the sensor. It was in close proximity to the coolant outlet connection on the engine.