With all the help I got here, I was able to get the temp gauge to consistently read.
Here is a picture of it reading about 75C with the motor running at the max rpm. BTW, the motor runs great!
What I did...
First, you saw that I had taken the T stat out before and replaced it, noting that the gauge read the temperature for a brief moment. So I figured the gauge was OK and so was the T stat. That's not to say I won't change it out later though. Anyway, I removed both sensors and touched each to ground and determined that the one on top was the one sending to the temp gauge. The other sensor did nothing I could determine?
The other interesting thing was when I grounded the top sensor to it's port in the radiator hose mount... even after removing the Teflon tape ... it did not send any signal to the temp gauge. However, when I touched it to ground on the water pump side, the temp gauge flickered. So the radiator hose mount is sort of insulated via the gasket I guess. In any case, it did not provide a proper ground.
Next, I saw that all (most) of the sensors were installed in the lower port, not in the bolt on part that connects to the radiator hose. That's why I ground the sensor to that port in the first place. I ended up switching the sensors. I put the one that did nothing into the top port, and the the one that's connected to the temp gauge into the bottom port. The threads were clean and I used a small amount of thread sealant. Then fired up the Jinma.
After a few minutes, the temperature started to rise on the gauge. After warming up we let her run at high rpm and she heated up to about 75C or so, as you can see in the photo above. That T stat in there is a 78C one so I thought it was close enough. Then we shut it down a couple time to see it the gauge continued to work and it did. So I think that's the end of the temp gauge problem.
Thanks for all your help.
