I suggest removing the gas tank and following directions on here to clean it. If it's badly-rusted, you may want to seal it. There are directions for that, too. The carbs are probably filled with crud and should be disassembled and cleaned. You can do it yourself if you're a skilled do-it yourself'er, or, and I suggest this, remove them, make sure they are well drained, and send them to dannymax or to Sean Morley, look at the banner ads at the top of the page. You will get them back, and all you will need to do is to install 'em and synch 'em, an easy, quick thing to do if you have the correct gauges, which aren't expensive, and which will pay for themselves the 1st time you use 'em, compared to having it done at the shop.
As-old as it is, it's not uncommon for the rubber donuts between the airbox and the carb tops, the bottom of the carbs and the VBoost manifold, or the O-rings between the VBoost manifold and the engine (requires airbox, carb, and VBoost removal to access the O-rings) to need to be replaced, They dry-out, and you get air leaks, causing poor operation. There are various ways to try to fix that, but the best way is with new parts. Sean Morley (
[email protected]) will be the first one to tell you, "O.E.M. parts only, please!"). There are aftermarket suppliers of the rubber carb donuts you can try, but you know O.E.M. fits and works best.
I wouldn't even try to run the bike on the uncleaned tank (a good thing to try to get it running on an exterior tank), and it would be a total waste of time and $$ to clean the carbs and hook it back-up to the uncleaned tank. Don't forget to change the gas filter, and check the gas lines. There is a molded-rubber T gas line in the carb block assembly, just do yourself a favor and buy a replacement now. As-old as your bike is, it will probably tear-apart when the carbs are disassembled. If you're sending the carbs off, it will be replaced. There is another molded rubber gas line you don't need to replace with the factory line, it's the U-shaped hose on-top of the gas tank, under the seat. You can just get a longer length of gas line, and make a gradual loop to replace it. Avoid bending it too-sharp, to-where it kinks.
A word on using an exterior tank, if you bypass the fuel pump and connect directly to the carbs: you need to hold the exterior tank well-above the bike, to give the gas some 'head' for the gas to-flow into the carbs. If you try to hang it off the handlebars, at the level of the handlebars, you won't have sufficient 'head' to allow the gas to flow sufficiently to fill the carb bowls.
I suggest using some product like Deoxit to clean the electrical connectors, and a dab of dielectric grease on the contacts before re-connecting things. Old harnesses are prone to corrosion. One place where you are likely to find corrosion and possibly a crumbling nylon plug is from the stator to the regulator/rectifier connector. Many people solder this connector ass'y. It doesn't matter which of the 3 wires goes to the other wires from the R/R. Just make sure you wrap w/tape or heat-shrink tubing the splices. Also, remove and clean/sand-down the R/R point of attachment, as the attachment
is the ground for the electrical system at that point (there are other grounds in the harness, one by the right engine cover above the footpeg) and it needs to be clean and tight to work. Dielectric grease between the R/R and the left rear footpeg carrier is a good idea.
You should also do the 'crimp-fix,' where you solder a critical wire connection inside the wire harness which has a brass crimp connector underneath the wire wrappings. It's above the battery, in the vicinity of the ignition coils, and should be done. Your charging rate will probably increase.
There are plenty of other things to do. Flushing your brakes with new fluid is one, the clutch too, and check the slave cylinder for clutch actuation, it's a known point of leakage. There are stickies on replacement of the clutch slave cylinder. You can clean the old one, and use a rebuild kit, I suggest just buying a new one, as parts are available. Same thing for the clutch and front brake master cylinders, I but new instead of messing-around with rebuild kits. For now, I would just go w/O.E.M., as people who have tried aftermarket master cylinders have encountered various issues with them not allowing proper brake or clutch operation. Bleeding the brakes and clutch systems, use a 'reverse-bleed' and the work will go much quicker. I used a Mityvac since the early 1980's when I got my 1st one, but on my VMax, a reverse-bleed is quickest, and it pushes any trapped air bubbles out of the system. Just be careful with the master cylinder, as you can end-up with spilled corrosive brake fluid on your paint and engine. Once you see a steady stream of brake fluid filling the open master cylinder, add additional fluid to fill the master cylinder to the proper level, re-cap the master cylinder, and 'fan' the lever a few times, you should get a firm brake or clutch lever quickly.
That should get you started.
