The Dyanastart is rated at 240 watts output: so using the dreaded school electrical formulas (I.E. simplistic calculations) Power = Current x Voltage.
Turning things around gives you: current = power divided by voltage > 240 /12 = 20 (Amps)
That would be near the maximum output from the regulator into a completely flat battery. As yours has a good voltage to start with it is unlikely to draw that sort of current, so you meter should be able to cope with what we are going to ask of it.
The first thing to do is find out the standing current loss and the current when you have various electrical items on. This will help you get the hang of how the cables are to be connected.
First off, every thing off,
Undo the positive connection to the battery.
Attach the positive lead from the meter to it. If you can make a connection system that allows you to leave it connected without having to hold it on to the terminal, that makes things much easier. A longish piece of bare copper wire wrapped round the terminal and then around the probe tip from the meter should do the trick.
Now the negative lead from the meter to the positive lead that went to the battery.
Meter on.
Hopefully you have 0.00 Amps showing.
Now turn on the side lights - this should show (2 x 3 watts front side lights, 2 x 5 watts rear side lights, 1 x 3 watts speedo light, you don't have a fuel gauge on this Hafi do you? if you do then you have to include that in the calculation - 2x3 + 2x5 + 3 = 19 watts:- so using the formula above; 19/12 = 1.583 Amps. So the meter should now be showing numbers very near to 1.6 amps. (Don't fret if the numbers are not exactly that - remember the battery voltage is not exactly 12 volts and there are loses in resistance at the joints etc)
The readings should be - 1.6 Amps as the power is being taken from the battery. If the reading was + 1.6 Amps then we have got the wires on the meter connected the wrong way round - I can never remember which way they should be, but I know I am expecting the reading to be a negative value!
You can add the headlights in now if you want to see what current that circuit uses.
Things get a little bit tricky now, as when the Dynastart is in starting mode it will draw up to 300 Amps which if you hadn't guessed will burn your meter out quite quickly!
The way round this is by having two people. one is going to do the standard starting sequence, the second has the cables from the meter to deal with.
You start by having every thing off of course.
Take the same setup as you had above with the meter connected in series with the battery cables. Take the positive cable (still with the meter wire connected to it) and touch it to the battery positive terminal - You have now "shorted out" the meter from the circuit.
Start the engine - the huge current will flow across the easy metal to metal path and not through the meter as the meter wire go the same place so there is no difference in voltage between the two meter cables.
Once the engine has started and the Dynastart has become a generator, you can "separate" the battery terminal and its original wire so the current has to go through the meter. There is no interruption of electricity so you should not have any strange hiccups or possible bad things happening to the engine or Dynastart.
You should now have a reading on your meter - if it has gone beyond 20 - then it will have blown the meter as your meter has an "unfused" 20 Amp setting. In which case it will show 0 or 1 and it will not change.
If everything has gone according to plan you will have a figure showing the charging current going into the battery. If the number is negative then we have the wires connected the wrong way - see above. With your digital meter this is not really a problem as it will show negative numbers as well as it shows positive numbers. With the old needle based meters more of a problem - which is why the ammeters you see in cars have both positive and negative sides for the needle to move to!
Anyway, to get back to your issue. with the engine running your figure should change as the engine revs go up and down. Hopefully not by a lot.
Remember we measured the current used by your side lights right at the beginning? The figure you are seeing now should be higher than that and if you turn the side lights on now, you should still see a reading which shows that the Dynastart is putting power INTO the battery. If the value changes from positive to negative (or the other way round) when you turn on the side lights, then you have a PROBLEM!
I'll leave the answer to that for another post if needed - this is long enough.