HI Dave,
In my experience, no, it shouldn't run with the metering screw (ms) all the way in.
We will need a bit more info from you about your bike though. What year? Have you owned it since new? Has it been sitting for a long time? How many hours on bike? What kind of gasoline are you running? Where do you live? Altitude, temperature, etc... Are you using the choke when you start it? Is the float level set correctly??
Here are a couple thoughts on your situation: Since you say that you cannot start it after turning it off without a long wait, it would appear to me that it is very rich. In your description of fiddling with the ms, the motor is slowing down because you are making it richer and richer until you've reached the maximum amount of fuel that that particular circuit in the carb can deliver or flow.
Usually, the way one tunes the motor at idle with the ms is to get it running and fully warmed up. Then adjust the idle to around 1300 or 1400 rpms. Turn the ms in until lightly seated. Take note of how many turns you were at, and reset the ms at that position. But in your case you would want to do this before you start the bike.
Now then, once it's running and warmed up, one would start by turning the ms in until the rpms start to drop off. Take note of how many turns you went in. Then start backing the ms back out until the revs start to drop off again, take note of the turns and or where you are at. Then split the difference, in other words go to the mid way point in relation to the turns out you are between the ms in rpm drop off and the ms out rpm drop off, and then 1/4 turn IN or lean.
However, in your case, it seems to me that you are rich. This can be caused by a few different things that come to mind:
1) Your choke plunger is not seating properly and allowing fuel to leak through: The delorto carb I have on my 01 501 would collect a bunch of crap in the plunger area and would need to be cleaned up occasionally. So pull it apart and have a look. Then make sure there is a bit of play in the wire so that it will fully seat. Once you take it apart you'll see what I mean.
2) Your float level is too high: A certain amount of fuel at idle passes by the needle jet and the jet needle (aka emulsion tube). I'm assuming here at that you are not getting fuel dumping out the overflow tube from the carb. With that assumption in mind, I think we can eliminate the possibility that your float valve and seat are in good condition. Also, make sure that one of the floats does not have a hole in it.
3) Your needle jet and jet needle are severly worn: These items do wear out and allow the bike to run richer and richer. If the bike is ridden allot these items might need to replaced every year. You said in your post that the carb internals are what the book says. Did you check the needle jet number and the jet needle number to see if they're the ones in the book? If they are severly worn excess fuel could be passing by here at idle.
4) Your vent tubes are kinked or clogged: If the float bowl vent tubes are clogged or kinked this would cause all kinds of problems for you trying to diagnose this problem. The vent tubes need to be clear for the venturi in your carb to work properly. So make sure they are clear.
5) You do not have the little O ring on the end of the ms: There should be a small O ring on the ms with a washer on top of it then the spring.
These are just a couple of idea's. My bet is that your choke is not seating all the way due to mis adjustment of the actuation wire/cord, corrosion or crud that is not allowing the plunger to seat properly, or the rubber pad at the bottom of the plunger is worn out and is not seating on the little tower at the bottom of the well. Again you'll see what I mean.
In closing here is another suggestion. If you have not already done so, completely tear apart the carb and clean it out. Keep the carb cleaner away from the pointed little rubber peice on the float needle, the choke plunger base, the floats themselves, and the O ring on the end of the ms. Use plenty of carb cleaner and compressed air to clean out all the passeges with all the jets removed. Sometimes the oil from the engine breather wll collect in the boot that attaches the carb to the frame, and then it will clog the air jet in the bell of the carb. Also, examine your intake manifold carefully for cracks.
By starting out with a clean carb, that has been properly spec'd, and the float level set correctly you wil have eliminted all of these possibilites. If the problem still exists it will be much easier to identify.
