Drive shaft bearing = the bearing behind the sprocket. If this bearing goes, the shaft goes off-center and oil seeps by the oilseal, resulting in a rapid oil loss from the engine, a very oily chain and rapid sprocket/chain wear. Unfortunately, if this bearing is shot, you'll need a complete breakdown of the engine to replace it, and depending on how long it's been shot (distance you did with it), there could be significant wear inside the engine and oil pump due to small metal parts distributed throughout the engine and gearbox.

That's the bad news.

Oil use: I found on my bikes and the AT, the 'older' the oil gets, the more oil the bike uses. I.e. the bike will not use any oil for thousands of kms, but then all of a sudden, the oil 'disappears' and I constantly have to fill up. I've done some reading, and if I understand it correctly, when the oil wear's off, the polymers that make it 'clingy' wears off and more oil stays behind in the cylinders and burns up through the exhaust. A good quality oil lasts longer than cheap oil, but according to Honda, any oil consumption upto a liter / 1000km is normal.

So just cause it uses oil, doesn't mean there's something wrong, but it's worth keeping an eye one and isolating 'when' it uses oil- e.g. if you do an oil-change, is it 'better' all of a sudden?

As for previous comment on valve guides- relatively easy to check: if you stop for a few minutes, e.g. at a traffic light, then pull off- is there a small puff of black smoke that disappears? if so- that's a leaking valve train.

Running against back-compression (e.g. down a hill, closed throttle with the engine doing the breaking) with a smoke cloud behind you = rings. If this is the issues, you should also see a lot of oil in the airbox or dripping out of the crank case breather as you'll have too much crankcase pressure.

These checks above can be done without any instruments/tools just by being observant when you're riding.

Last but not least- spark plug foul: if there's too much oil in the cylinders (for whatever reason), you'll start to foul the plugs with unburnt residue. In fact spark plugs can tell you a lot of what's happening in the engine
Spark Plug Troubleshooting - YouTube



Good luck!!!

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Squily