You know what needs to be made in clear plastic? FLOAT BOWLS. It's practical, you could see if there's a problem, if there's gunk in them, etc. The DOHC Honda factory racers had them, though I'm not sure whether they were plastic or something more like corning-ware, whatchamacallit-lab-ware glass, etc. I think they were on CR carbs. If you could make them for those carbs alone, you'd sell a bunch. But put them on all sorts of other bikes, and it's bound to catch on. I dunno how it would be done, or what material or anything. Maybe cast lexan. THAT would be cool. And the thing about the clear covers, is they don't make any sense with a non-points CDI ignition. Or a wet clutch, especially if your oil gets dirty fast. Dry clutch, it's far cooler no pun intended, to have the clutch cover vented for air flow, though I suppose the bugs get in that way. It's cool that there are bike parts coming out in new materials, just not the ones I want. Something else that would be cool would be brake-light and signal covers that have a vintage vibe to them. So that the lights from all of the modern crotch rockets could have a little more class. I know, that's a HUGE challenge. Ha ha. But I bet there are some of them that could be helped. Oh, and you know those leg-shields on the Honda cub? THAT needs at least a few examples made in clear plexiglas. Though, it also needs painted fibre-glas ones with a chromed steel trim around them like a crash bar. As for the cheap plastic, that's where you need some good gas tanks. You can get an enduro tank to put more gallons on your dirt-bike, but you can't get a copy of a Dunstall or Manx tank in those materials. Bubble fairings too, why can't you get a nice cafe fairing in cheap hot moulded PVC? Okay, that's not as important as the gas tanks they DO make being constructed of fibre-glas, so they look great until they crack in an accident and stop looking good because you can't even see them through the wall of FLAMES.... Ugh. I'm thinking, "flow-formed" alloy, brazed together in batch kilns with "aero-braze" and "nocolok flux", you could under-cut the fibre-glas tank people no problem. But yeah, for the time being I'm just gonna complain about the lack of clear float-bowls. I wonder what other superbikes raced with them, there might be a pretty good market for that reason alone. But I think the practical reasons would encourage their use elsewhere.
As for making a clear cover for the widest point of most engines, it would be cool to see them moulded really tight so that they give a slim appearance and better corner clearance. I'd bet that most of them could lose close to an inch. That would appeal to a lot of the AHRMA crowd as well. The good thing about plexiglas is it's so easy to glue and seal. I used to make a lot of custom aquariums, terrariums, paludariums etc, out of acrylic. The important thing to do is to "flame buff" the cut edges after first burnishing them with the back edge of a hack-saw blade. One could well imagine a side cover using a flat plate and a little bubble from one of those coin machines with the crappy kids' toys in 'em. Better still, would be a sheet heated until quite soft, then lain over the ignition to take a shape, then filed and burnished and polished down to a beveled edge. That would be a great part, even if you painted it to match the aluminum. Of course, plexi's not the right plastic for the heat and everything, but perhaps lexan? How about an air-box? The lunch-box type air-box on the "sand-cast"/"die-cast" CB750K, in a clear acrylic so that you can see the state of the air filter the fit of the rubber boots, etc. Even side-covers, they could be made in a thin clear plexi, and painted on the inside, then it would be like a really thick clear-coat. Even better in a coloured clear plastic, like the stuff on the late-'90s model Buell bikes. Loads and loads of great uses for the stuff. It just takes somebody willing to mass-produce the things to make it worth-while economically speaking.
So I really hope this stuff takes off for you, so that you can diversify your product range, then I can get some float bowls some day. Ha ha.
-S.