Just went through a similar thing with an 2003 Volusia. Here are the many different ways my bike would NOT start, and after correcting all these issues, it runs well:
1. Rust in tank, fuel lines, fuel valve. Diagnosis: disconnect fuel line from the carb, point it into a safe container, crank the engine, see if fuel comes out. Fix: replace fuel lines, take apart fuel pump and clean it (factory manual would have me buy a brand new one, but at $100 I figured I'd try cleaning it, and it worked).
2. Loose vacuum hose at the petcock. Diagnosis: hear wooshing sound. Fix: plug it back in.
3. Idle RPM screw (not the mix screw) set too high, and throttle cables too tight. Diagnosis: this one took some hair pulling, but is obvious in the end. The bike would only start with a "manual" choke as in taking off the air intake and putting my (gloved) hand over the carb to let almost no air in. It would fire up briefly like that. Finally it dawned on me that the throttle might be partially open at idle, which would give it way too much air even with the choke/enricher on. Fix: take the idle RPM screw to nothing, try to start the bike, screw it in half turn, try again until it goes. Make sure there is a tiny bit of slack in the throttle grip to know that the pull cable isn't pulling on the throttle.
4. Bad gas. Diagnosis: is it old and/or does it smell bad? If so, drain the tank and replace with fresh gas. I created a DIY vacuum bulb out of a small hand sanitizer bottle and a bit of plastic tubing glued into it, but you can use a syringe too to actuate the vacuum petcock and drain the fuel nicely.
5. Incorrectly set carb bowl height. Diagnosis: I knew this is what happened because I tried to set it and the bike wouldn't start after that. On a carb like this, it is a huge pain in the behind to set the float height because they want you to hold it at a 45 degree angle when doing it so you have to rig up some kind of plane to do this on. Then you need a digital caliper to measure it. Fix: read the manual and watch YouTube videos for how to do this until you understand the theory, then attempt it.
6. Weak battery. I don't know if you can bump start these bikes, I never succeeded. With a weak battery it might crank but doesn't seem to want to actually start. Once it gets going though, it's fine. Diagnosis: measure the voltage or take the battery to any auto parts store. Fix: get a Battery Tender or equivalent or a new battery.
7. Valves out of spec. The bike did run with this but (a) valve noise was obviously too loud and (b) would surge/lope around idle. It was unpleasant to ride it like this because if I am going in traffic and have the throttle at idle, it would surge forward periodically, then engine brake hard. Fix: adjusting the valves and idle mix screw. Valves have their own guides on this forum. Idle mix screw: use a digital tach to watch the RPM with the bike warmed up.
I think that was about it for what I had to go through. I still have to run it with the choke 1/2 to 3/4 on for about a minute or two before it runs smoothly without it, even in 90 degree weather. Good luck, hope this was helpful.
Last edited by ipartola; 07-18-2019 at 09:50 AM.