I installed a sight tube after my filter. i.e. Petcock-filter-hose barb T- carb. The T is inverted to let any bubbles go up and out. On the top end of the sight tube I have a stone filter to let it breathe. Works like a champ. Simply look down and you have instant reading.
However, there are disadvantages to this rig, as I found out this morning. Inorder to to connect all of this together I ended up with a coiled snake up under and between the frame and engine. It all fits where the carb used to fit. (it's a 91 Tomos A35 auto step through) After hitting a small pothole today the line became kinked and severely reduced the engines output.
It wasn't until I returned to the Batcave that I found out what the issue was. All I had to do was strap the hose to keep the line smooth and could have been repaired in the field, but I was only about a mile from the house and i was able to limp back about 13/16ths of the way before actually having to push it.
I didn't come up with this idea. Some genius on this site did. I just thought it was such a neat idea that I'd try it. I highly recommend it.