Check your battery first. If it's not getting charged well it may not be providing enough spark. Sitting a few minutes without load may allow the bike to restart because the battery has recouped a little.
The connectors from the stator to the voltage regulator are sometimes a problem on these bikes, as is the voltage regulator itself.
There are several notes in the vulcan verses as to how to check the battery and charging system on the vn 750.
I'd start with electrical though, that seems to be the weak system on these cycles.
Keep us posted with findings, we will try to figure this out with you.
Another suggestion. When this happens again, open up the gas cap and try to start the engine. If it fires right up you have a gas cap vent problem or a bad vent line. A hot engine or hot temperature could be creating this problem.
90% of all hot starting problems are solved by installing a good AGM maintaince free battery....so start with flite's suugestion first.
It helps when you post about a problem to give as much info as you can, so you should let us know what year your bike is, how many miles,and in this case, what type/brand battery you have, how old it is, how old are the spark plugs, if the gas tank is full with fresh gas, and how well the bike runs generally. The more info we have the better and faster you can get usefull suggestions for help.
Vulcan 750s are known for hot starting problems. Mine has it, sometimes it takes 3-4 attempts to get it started, and before it starts, it will sputter and backfire a few times. I mean just a tiny pop or 2, not like a 12 gauge. Nobody has come up with a definitive answer for this, it may well be more than one thing, but I do believe it is a design issue, since virtually all of them are affected.
I believe the biggest problem is electrical. I think it is caused by a weak spark while the starter is turning over the motor. But, I don't necessarily blame it all on the ignition system. I believe the starting system is also at fault. I have noticed from the time I bought my first new Vulcan 750 in 1993 that the starter turned the engine over really slow. It's not the battery, though a weak battery would make it worse. I have connected batteries to it with enough CCA to start a 5000 hp top fuel dragster, and the starter still turns slow.
All my other bikes, and my former Ninja 500, turn over twice as fast, and all of them start right up, cold or hot, unless they have been sitting for a long time. I don't know what causes it to turn over so slowly. A 750cc engine should turn over 1000 rpm with just the starter. And if it would, I think the starting problem would go away.
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