Sight Tube

I do not leave the OEM one in. I use the SS one from XRsonly. I don't drill it or anything. Some will argue for not using a thermostat but I'd argue it's necessary. You need something to hold the coolant in there long enough to absorb the energy off the cylinder walls. Heat is horsepower but also there's all that expansion of metals engineered into it that requires a certain temp range for longevity.

Anybody have a .pdf?