I spent all day today working on 3 sets of PD46 carbs. Actually 2 and a half sets as the 3rd set was sans bowls and floats. I purchased this '78 about a month ago after it had been sitting for about 20 years. It's owner 'attempted' to get it going but failed, and rather butchered the original carbs. After spending all day today I finally managed to get the original set working, which included replacing the slide on #3. But, all 4 carbs were torn down completely, virtually everything removed and cleaned, and then re-assembled. Took some time, but I finally figured out the idle passage scheme on these carbs. The mixture screw controls idle fuel from the slow speed jet.....but there IS another passage found under the slide area and almost directly above the slow jet. With the slow jet out, a spray of carb cleaner will produce a small spray out that orifice. If you remove the mixture screw and spray up there you see the stream come out AFTER the slide (front side). You can also spray into the air bleed and see fluid out both orifices, particularly if you hold your finger over the opening for the slow jet and the mixture screw. So, I believe this second and obscure idle orifice would be considered a 'transition' port. The only control over it's fuel delivery is the slow jet itself.
So, based on my original question...... I'm unsure of just how to go about 'adjusting' the idle mixture screws in the absence of having a CO meter in each muffler. I figured someone had to have a 'trick' to it.....but I'm wondering if there's a typical 'start' point and popular process (sorry....'question mark key on my laptop is non-functional). Just for the record, I set all my floats at 13 mm, my needles are now on step 3, I'm still running 90 mains, and 42 slow jets. I set the mixture screws at 2 turns out in my bench set-up......and did a 'bench' sync on the slides. I don't have a multi-cylinder vacuum synchronizer......but looking at them on ebay. Any suggestions on which one would also be appreciated. But, assuming the sync can be done properly....how do you verify actual 'mixture' adjustment (question).
