New Reproduction Gauge Shells
When I picked up my 1972 Suzuki GT750J rebuild project, there was an obvious issue with the gauges. The gauge shells for my speedometer and tachometer were cracked, and when I started asking around I found this was a common issue and specific to the 1972J model. Some folks have tried to glue up the shell, but I do not consider this to be a long term solution - and of course if the crack has extended up into the lens then the shell is scrap anyway.
So - I had copies of the original shells recreated by a company here in Canada - currently just of the speedometer and tachometer as the water temperature gauge is normally in good shape. The material used is polycarbonate for the black case and an acrylic for the lens, which is then solvent welded to the case. Each solvent welded seal has been water tested to check that the joint between the clear lens and the black case is complete. The speedometer shells are pre-drilled for the reset arm spigot (which I do not include - you reuse the old one - see next page). In the photos below, the original is on the left and the copy is on the right.
And here is a photo of the trial fit of a new speedometer shell, re-using the reset knob spigot from the old shell:
Replacing the shells is not difficult, but typically that isn't the only repair required. Usually the needle needs to be repainted, the dampening fluid needs to be replenished (to dampen needle bounce), the instrument mechanism needs to be cleaned and calibrated, and the trip and odometer reels rejuvenated with new numbers. Possibly the face will also need repair.
If you need a major gauge/clock repair then check the list of clock/gauge restorers and sources available on this page elsewhere on my web site to see whether one of them might possibly be able to assist.