My bike makes a loud whining noise on acceleration in all gears, and more of a quiet whining when at a constant speed. It sounds like an old school supercharger almost, but inside the engine. I've been told that carbs being out of sync can cause some strange noises...think thats what this is? It's REALLY noticable, more so than any exhaust or wind or other normal bike noises.
There's a couple of things that can cause this: most common is one of the tranny bearings having been starved for oil at some point, now slightly pitted. The pits on the ball bearings are making that noise. Usually, this happens to the countershaft bearing when the small oil seal behind its retainer was either removed by someone (accidentally) and not replaced, or if the retainer was removed and reinstalled with the old, cooked-flat O-ring inside, which then leaks oil instead of oiling the mainshaft and this bearing. This is found more often on the post-1976 bikes because of the taller 1-2 gears and resulting load on this bearing.
You can try this to see if it quiets it down: get some of the 20w50 Mobil 1 oil for the V-Twin motorcycles (found at most auto parts stores), replace oil and filter and ride for about 100-200 miles to see if it gets quieter. If it does, you'll have to change that bearing before you go riding coast-to-coast on that one.
