beta zero gara

Ethanol and methanol have higher octane rating to begin with, but this only matters in very high compression engines with dramatic advance curves on their ignition. Trials engines do have higher than normal compression but they don't rev much and the ignitions don't need to be so aggressive. What happens with eth/methanol even when used as additives to improve octane rating is that the fuel/air ratio is affected. The engine will run leaner and that will cause more heat. Hotter engines may run into trouble with pinging and dieseling while running lean. So you can kill a good engine running premium fuel if you don't adjust your jetting to that specific fuel. The only alcohol that will run right and have higher octane is butanol. It is harder to find and it is a carcinogen. More oil.fuel ratio will result into a leaner air/fuel mixture as the extra oil displaces fuel from the formula and oil doesn't really burn all that well. So you may have an oily plug confused as a rich plug on a motor that is about to seize-up from being too lean. That pump premium gas that you pay dearly for, they may have brand name formulations for it Race/Ultimate etc., I believe is just diluted gas/petrol with alcohols and maybe some synthetic nasty stuff. If straight regular gas doesn't goes preignition and overheating there is no need to pay for anything else. Manufacturers make money and have their owners/service manuals printed free by Fuel/Oil industry to add their crap into it. If you see some fuel/oil brand name on the owners' manuals just ignore all the crap that relates to them

Most of all the parts you would wear out and need are not unique to the model. Some of the engines were used later even when the water cooled bikes came out in models that were not intended for competition but as play/practice/trail bikes. I am not an expert on those but I assume some parts are interchangeable. Bearings and seals have measurements and can be obtained from a good local shop. Pistons and rings can come from the few manufacturers that still make pistons and rings for just about anything. I'd try Wossner before anyone else. Beta in UK in my experience has been more helpful and knowledgeable than even Italian parts sources. (maybe there is a language barrier but I run into quick dead ends) For everything else you can improvise some. As reliability goes, my Beta has been more reliable than any Japanese 2stroke I ever owned. This alone should tell you enough that if the bike runs well keep running it. Letting idle for long will eventually cause a problem.

Yes, I called it a gearbox (a transmission) there is no such thing as venting a crankcase on a 2stroke, it relies on its sealing for building compression. The port induction of the distant past had the piston block the intake while it was going down, the reeds are a form of a one way valve, and the rotaries had the crankcase venting at part of the stroke and then shutting the rest of the 2 strokes through a rotating disk going past a window. The gear boxes on 2 strokes are isolated from the crank, unlike modern 4stroke motorcycles which use the same oil in crankcase and gearbox. Although on some of them when main crankseals go (depending on the arrangement) compressed air escapes to the gear box, sometimes pumping the oil out of it. They usually don't run well enough or long enough to cause tranny damage. On some water cooled the oil is separated from the water side of the pump by a bearing and seal system. When that goes bad the bearing goes bad as well and steam/coolant pumps into the tranny. Which is one reason mostly 2 stroke street bikes will have that vent pointing away from the rear tire, for obvious reasons.

The gearbox doesn't really breath much (unless there is seal damage somewhere) but some expansion may result from heat and splashing around of the oil. Other than dust the reason for the hose is water intake. A hose running up then back down again or in the airfilter is a good idea in case you ever run into a deep mud hole or cross a creek. A little spongy material (maybe a small piece of an air filter) tied up at the end of the hose might be good. It will soak up some oil vapor and prevent moisture coming in when the bike cools down.