In my experience, there's no great difference in fuel pressure regulation or float height: the paso runs good with float at 44 or 48mm and the extra pressure will flow back to the fuel tank; best help from a pressure regulator in the bypass is to prevent vapour lock in the fuel pump.
In order to help you, here are my suggestion to fit a proper tuning to vacuum balancing:it's quite a work but it will make your paso run very fine!
First of all:
How to build Your own vacuum balancer
Components:
1) plastic trasparent (neutral color) pipe, diameter 8 mm (3/8 inch), about 2 meters (6 feet)
2) fuel pipe (or similar) about 4 meters (12 feet)
3) one 8 mm tap
4) two small tanks for fuel pipe (fuel filter #0370083350 original ducati or similar will do)
5) two holed nozzle screwed 5mm (these must fit on the fuel pipe too!)
6) one standing (about two meters,see picture)
7) blue water color
water , one glass
assembling:
Cut in two parts the trasparent pipe and put the tap between them
Put the tanks at the end of the two pipes
Cut about ½ meter of fuel pipe and save it
Cut in two parts the rest of the fuel pipe, and put them on the free ends of the fuel tanks
Fit it upon a standing, the tanks on the top and the tap about in the middle
Get the water color ready, just some drop of color in the water (you don’t need to paint anything)
Put the water inside the pipe, just to fill 50% of the pipe
Screw the nuts on the inlet mainfold duct, under the carburettor (you will find two standard screws in the place; you can see the workshop manual, adjustments chapter, idling adjustment, image 22.gif and 23.gif)
Put the rest of the fuel pipe between the two nuts on the engine
Using the vacuum balancer:
_First of all you’ll need to be able to reach easly the carb, so you’l have to put the fuel tank off and provide a different fuel inlet to the carb.
_ Insert the two ends of the pipe in the two nuts you have screwed
_close the tap of the balancer
_start the engine
_open the tap.
_Now you can see how the two cylinder inlets are balanced: the water level in the plastic pipe will be skipping colse to the average vacuum level. The difference between the two levels will show you how to work: 10 mm (5/16”) is quite good, more needs to be corrected.
_Fear not to see the water flow into the engine, as a very small quantity of this will not damage anything, moreover the small tanks at the end of the plastic pipes are fitted there in order to receive the water before it’s going inside the engine.
Tuning the vacuum balance
This is the absolutely hardest thing to do. If you aren’t skilled for this, STOP NOW!!!
Otherwise you can start working on the carb.
In the workshop manual you can find how to make an idling adjustment, see 22.gif and 23.gif
Anyway it’s not enough! YOU NEED TO FIT IT FOR BEST PERFORMANCE ON MIDDLE RANGE OF RPM!!! so:
Turn slowly the forward handle until ~2000 rpm
Watch the water levels: they often happen to be unbalanced, compared to the idling adjustement. It happens because of the lever and throttle shaft clearance!
This means that the throttle of the orizontal cylinder opens more than the other and this makes the forward irregular.
So, that’s what you have to do:
Stop the engine(of course!)
With your hands, turn the throttle shaft colckwise on the pump side, and with opposite spin on the lever.
Test the level again (close the tap before starting!)
If the handwork is not enough, try with some tool to lock the throttle shaft on the pump side and handle the lever side. YOUR MAIN PURPOSE IS TO SAVE THE SHAFT FROM ANY DAMAGE!!!
Repeat the test and the work until vacuum lever at 2000 rpm will be good
Repeat the test at idle. You’d better have a good balancing at middle rpm range than a good idle.
tuning the mixtire
you will need to install the airbox filter to tune it properly.
Spin one of the screws of mixture clockwise until the end; if the engine stops, unscrew for one turn and start the engine.
now spin it unclocwise for 1/2 turn each step... wait for a while and listern the engine running. When the idle speed begins to grow, you are near to the right tuning: the highest idle speed you can reach is almost a good tuning.
An additional spin of 1/2 turn unclockwise will get the mixture "rich"
If you can't see a great difference in regulating the screw, spin it again clockwise 'til the end and repeat.
Do the same thing to the other screw; maybe you'll need to do again the work on the first part, just for a bit of additional tuning
A rich mixture will help you in riding
You can see my carbureteur balancer here:
http://it.msnusers.com/pasochisti/shoebox.msnw
Have a nice work!
Nicola