Or if you want to take your front fenders off you have to drain the radiator.
I went through 3 mechanical and 1 electric water temp gauges. 1 Equus, no name brand, and 1 autometer. All three faild. The vibration would tear them up. They were all 2 1/16 in mechanical non liquid filled. a liquid filled gauge is what you need, but you can only get a liquid filled gauge in 2 5/8 in. It was to big for my taste. I didn want my banshee looking like a 80's honda civic with a 5" tach.
Here is my electric one that failed.
Mechanical Equus