[DEMON]

here are some quick notes :-

1. if you were to measure the dc voltage at the battery at idle you will prob find it to be around 12 - 12.5 volts. Rev the bike up to 3-5k revs and it should increase to around 14.5v dc.
answering your questions :-

1. Substantial voltage from the alternator - unlikely unless you had a problem in the windings.
2.The AC voltage readings are more or less correct, but you dont mention any rpm values to cross check these. A new gen would poss give lower readings.
3. You are measuring voltage not current wulfie, and the AC voltage fluctuations are normal, changing in relation to the engine speed.
4.A blocked fuel filter will cause engine running problems more than affect the voltage. If your bike is running rough, then it will efect the output from the alternator accordingly
5 you could and this could be battery voltage.

a good check of all your connections is required, both batt side and reg side to ensure you have no points of high resistance. check your earths etc too...let us know what you find ?