The Vulcan 750 has several known issues. Most can be fixed and stay fixed.
1. Final drive splines. The final drive splines were apparently not lubed at the factory. If you wait until the maintenance schedule recommends lubing them, there will be some damage. If you don't lube them at all, the rear drive unit will be destroyed. And decent used ones seem to be drying up.
2. Cam chain tensioners. The oem cam chain tensioner design is defective. You can replace them with oem units, which last around 10,000-12,000 miles, and then have to be replaced, or you can replace them with TOC manual units and be done with it.
3. The POOGS problem is caused by improper gas tank venting, which is caused by the emissions crap. Remove ALL the emissions crap, and make sure the tank is vented to the atmosphere, and it will go away permanently. If you have a CA tank (and CA bikes were sold all over the country) with 2 fittings at the rear of the tank, attach hoses to both of them, and run them through the holes in the frame and down under the bike. Leave them open. If the vent should fail, the other one will function as a vent.
4. The 3 wires from the stator have bullet connectors in them between the stator and the R/R. These tend to get loose, develop high resistance, get hot, and burn the wires around the connectors. I soldered mine and used heat shrink tubing on them. I believe this may have something to do with stator failure.
5. Stator failure. I really don't know if the Vulcan 750 is more prone to stator failure than other bikes, but when the stator does fail, the only right way to replace it is to pull the engine. So it is a major issue when it happens, and it is one thing that there is no known permanent fix for. TOC used to make a 2 piece left side engine cover which allowed the stator to be replaced without pulling the engine, but it cost a fortune, and required pulling the engine to install. I DO NOT recommend the "tuxedo mod" under any circumstances. You are literally dumping metal shavings into the engine.
6. Balancer dampers. The gear driven counterbalance has rubber dampers that tend to deteriorate over time. When the fail, they allow the balancer assembly to cut right through the engine case. They are not expensive, and should be replaced when you have to replace the stator, or any time you hear a grinding noise coming from the left front of the engine. Replacing them also requires pulling the engine.
7. The "coffee grinder issue" This makes a loud noise and causes the clutch to be very grabby. I have encountered it a couple of times. I found that it does not happen if the engine is properly warmed up and the clutch is freed up before releasing the clutch in gear with the engine running. I have found that the Vulcan 750 clutch tends to stick even overnight. I put the bike in gear, pull in the clutch, and rock it back and forth to free it. You can also put it in gear, and start it with the clutch pulled in, but be prepared for a lurch forward.
8. The R/R and junction box. There may or may not be an issue with these parts. Some claim that they can contribute to stator failure. I have put around 180,000 miles on 2 Vulcan 750s, both bought new, and while I did have to replace one stator, I never replaced either of these parts.
9. Tool box door. Not a big deal, but annoying. The tool box door on the backrest was designed to break. I can't believe Kawasaki designed it like they did. Mine broke, I got a new one, and never used it after that. I have the extended backrest, and use the seat with the bolts removed. The front tang and pad on the extended backrest hold the seat securely in place.
10. The shifter linkage. Early models had a defective shifter linkage that could fail at any time. It was changed after the first or second model year. But there is still an issue with the shifter. If the bike is dropped on the left side, and the shifter hits the ground/street/driveway, it can break the retainer clip and allow the shifter shaft to slide in and out. They did not put anything solid behind the shaft inside the engine to prevent this from happening. Fixing it right means splitting the cases, bu8t there is a way to0 rig it, by putting a spacer on the shift shaft between the shift pedal and engine case to prevent it from moving it in and out.
11. Hard starting and starting on one cylinder. The Vulcan 750 has always had a starting issue. Nobody seems to know why. Sometimes it will start right up, sometimes it takes a while to get it started. On both mine I've also had problems with them starting on one cylinder. The other cylinder eventually kicks in, but it can be annoying. This seems to happen after the bike has been sitting for a while. The petcock and some carburetor parts can be damaged by ethanol gas. I just discovered the petcock is leaking on my recently acquired 1997.
The Vulcan 750 is by no means perfect. Just because all these issues (and probably some I forgot about) exist, that doesn't mean you are going to encounter all of them. I believe it is seriously over complicated, with about twice the engine parts it actually needs. But that may well be the reason it runs and rides so well. When all is right, it is a magic carpet ride. It can take you across town or across the country, with plenty of performance and comfort. It is a perfect solo touring bike. I have had 2 Harleys, and currently have a Sportster 1200. It's wonderful for shorter rides, but the vibration and noise, the very things that make it so much fun to ride, become tiring on long rides. The Vulcan 750 never does. After my second Vulcan 750 bit the dust after 108,000 miles about 2 1/2 years ago, I recently went and bought a nice used one. Despite all of it's issues, it is still a wonderful bike.
I am a motorcyclist, NOT a biker.
1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike