Sure its glass? Mine sure feels like it but I've never had it out. If they're just small waterspots maybe softscrub with a fine steel wool pad might work but if its plastic, it will scratch it. I've used 'The Works-Tub and Shower' cleaner to remove hard water stains from glass shower doors. But years back we had drinking glasses become etched to the point where nothing worked. But that was after years of hard water, not an occasional splash spot.

Hope that is a help....

 

Finally figured it out. There is a fine coating of plastic on the inside of the glass, probably to keep it from fogging. The water drops etched themselves in the plastic coating. After taking a razor blade and scrapping
all the coating off(which took a good while) the glass is perfectly clear. I put a coating of Rain-X Anti-fog on it so Ill see what it does. I may end up buying a new speedo in the long run but at least it is perfectly clear now.

 

Just wondering....this water came from washing your bikes? Are you using power washers or a hard spraying nozzle? Is the water coming up from underneath or through the side seals of the glass? Would a very small bead of clear silicon sealant on the outside help if its coming in from the top?

I use a water hose to wash my bike, one with a gentle water flow to let the water pour over instead of a real hard spray. Always been afraid of forcing water into something somewhere that would cause me problems.

Glad you found a way to get the spots off. Wonder why the plastic is there n the first place...

 

The water was from a rain storm a while back I think. It was just condensation that formed in there and then dried leaving the spots. I have never used a force of water washing it and never noticed any water in the speedo when I was done.
I was using a semi rought scouring pad to clean the glass with CLR and
noticed some coating coming off so I got a razor blade, the kind you put in a paint scraper and started scrapping. Never did scratch the glass and I was scrapping pretty good but all the coating came off. Looked like a urethane coating or something like that.
Looks great now.