I went back and reread this whole thread, and I agree with Cindy back in post #2. You should contact the BBB or Chamber of Commerce or whatever similar local business association you have, and register a complaint against the dealership shop. Gather up all the paper work you have, including all estimates, work orders and invoices for work done. Especially note any written notes or remarks the mechanic or service manager made on the work order that should be returned to you when you paid the bill. If there is any mention of "push rods" on your bike, highlight it. 750Doug is right, there are no pushrods, only chains and overhead cams. Also make note of any mention of rust in the tank, written or verbal as you said above. Did you have to pay for all the other visits to the shop for adjustments, or just the $1097 mentioned for the partial overhaul?
I think you may have a good arguement to get reimbursed for at least half of the $1097 you paid for the "overhaul", and all charges for any subsequent adjustments. You say the service manager let it slip that they knew about the rust in the tank, at the time of the overhaul and did not fix it or tell you, so you could fix it. Therefore any visits to the shop after that time were a result of their negligence or incompetance. Before doing any more work on the bike, talk to the BBB as Cindy mentioned, and see what they can do for you. The dealer may offer to take in your bike and set the tuning on the carb and make it ready to ride, since you have already cleaned the tank and carb. Maybe they would also clean or rebuild the petcock and clean or replace the fuel lines, as well as anything else related to the work that should have been done the first time. You will have to decide whether you trust them touching your bike again, after enduring their seeming incompetance. Another option may be a credit note you can use to purchase merchandise, if they won`t refund cash. Just some ideas for you to consider. The more flexible you are, the more likely you are to get some satisfactory results.
You say that the tank has now been cleaned of rust. Was it treated in any way to prevent a reoccurance of the rusting? There is an article in the Verses called "rusty tank", which describes a simple method of treating a rusty tank at home, that coats the inside of the tank to prevent future rusting. I recommend reading it, although I have not tried the procedure myself.
Regarding syncing the carbs, I used the search feature last night and entered the words manometer carb syncing, or something close to that, and came up with one or two informative threads. The main jist of what I read , seems to indicate that most of us do not need to worry about checking it if our bikes are running well and smooth. If your bike is running rough or with a lot of vibration, or if you have done work on them, that maybe an indication that syncing is needed.
If you have the carbs off already, Cindy has an explanation up in post #5 about how to set the throttle plates to start opening at the same time for both front and rear carbs. In the case of a two cylinder bike this visual/manual procedure is probably all that is needed. This is what the syncing procedure is trying to achieve. According to the thread I searched out, an engine with 3, 4 or more cylinders will need more frequent syncronizing simply because of the greater complexity of balancing 4 carbs instead of only 2.
I`m not sure what your idle problem is, but try this. Count the number of revolutions it takes to turn the black idle adjust knob all the way in clockwise. slimvulcanrider said a few days ago, that turning it out about 2 1/4 turn ccw from here should be close to where it needs to be. If you were significantly more or less than that, maybe it will start and run now. Sorry for being so long winded, but that dealer ship screwing you over like that, p`d me right off. I hope something I`ve suggested here helps. Good luck.
1991 VN 750 -"Cosmic Lady
" or "Bad Girl
Purchased May 16, 2008
Approx.19,300km (12,000 miles)
Fiamm Freeway Blaster horns
F&S luggage rack and engine guard
Kury Offset Hiway pegs
July 13, 2016, Riding on the DARKSIDE now, Classic Radial 165/80-15
TOP TEN THINGS A NEW RIDER/OWNER SHOULD DO.
Click on link.