In this engine (CB750 SOHC4), there are 2 places where a [set of] these baffles works and makes sense. Underneath each rod, as is found inside the CB160 and CB72/77 Twins, a small flat sheet metal plate, the width and length of the area, minus about 1cm (that's Pops Yoshimura talk) overall size, traps oil that flings off the rod and crank weights. It falls below the plate and will not get splashed back up at it, so the plate can have holes in it, or like Bwaller says, it can be mesh. It is this splashing action that slows down the rod as it comes back down for its next swing by, particularly at the speeds these engines operate.
In some of the older small Honda engines, like the [rare] 90cc and 125cc hi-po twins (and the famous 50cc Four from the early 1960s), there are/were such windage trays in the tranny, too, so the splashing oil did not drag on the spinning gears. In the 750 this isn't quite so important because it is a dry sump in that area, but in the smaller SOHC4 engines it DOES make a difference, if hard to implement. That's not to say there IS an area where it can matter in the Big Four, though...more in a minute...
To make one, you usually must weld some small bungs into the bottom of each lower crankcase well, not a simple task. There just isn't a good way to try to do it otherwise, as any thru-holes there will weep oil in the future. In the midget-car racer engines, this was how it was done: each rod well got 4 bungs with 1/4-20 threaded holes and socket-head cap screws with safety wire holes in them, holding down the windage plates. Since the transmission was cut off of these engines (the oil pump was run off the camshaft with some other mechanical trickery) they did not use such a tray under the countershaft gears, but in the 750 bike [whole] engine this is where it can help. This one can be accomplished by making a sheet metal plate in the shape of the oil pan, with slots and holes cut thru it to clear the various obstacles and bolt in with an extra oil pan gasket: it is mostly only trying to clear the 2 larger inner gears. This was done on a couple of roadracers I remember from my 'circuit days' in the early 1970s.
In the 750, there are a couple of places where Honda implemented this already. While I am sure their intent is to prevent oil weepage in those areas, it also reduces 'drafts' and oil splash that creates drag. You can recognize it by looking at the tranny cover gasket, with that big flap of paper surface that separates the moving parts from the outer joint seal area, and on the back side of the alternator's gasket where the whizzing starter gear could otherwise fling the oil against the joint at the top right corner of the alternator cover. In some other Japanese bike engines I have seen (Suzuki comes to mind), the manufacturer used similar gasket treatments to reduce airflows and oil splashing both to improve oil retention (it stops oil misting) and improve upon crankweight and/or rod 'drag' due to flying oil droplets.
