I have a 2016 harley street 500. In any of the gears after I add more throttle half way through I wont advance as much and it just sounds like I'm in neutral. This is my first bike and I'm not quite sure what the problem would be.
As suggested by other members, it can be a case of either a worn out clutch or a loose clutch cable/adjustment. I don't see another probability like your vehicle ECU cuts off fuel supply beyond an acceleration limit or such but as you mentioned as the rev increased without acceleration, it won't be the case.
The HD owner site FixMyHog notes that HD recalled a bunch of 2016 bikes due to the clutch master cylinder not fully disengaging the clutch. This could result in your clutch disks wearing down sooner than normal. Check if your bike was affected by the recall.
Another suggestion: find the clutch engagement point. With the bike stationary, in 1st gear, and the clutch lever fully squeezed, increase the RPM's. Then, slowly release the clutch lever. In my experience, you should have to release the lever roughly 75% of the way before you see (or hear?) the RPM's begin to fall and the bike begins to creep forward.
If the RPM's begin to fall and the bike begins to creep forward after releasing the clutch lever...
- 90% of the way: the clutch disks might be worn
- 10% of the way: the clutch hydraulic system might need to be bled
Additionally to the clutch cable (or pump if it's a hydraulic one) you might need to check your OIL and clutch disks. Your bike is quite new so i don't expect it to have a big milage but if for example you made a bad oil selection (not having the recommended by your manufacturer standards, without anti-slippery factors etc) you might damaged the clutch disks. The same goes if your clutch has been unadjusted for quite a long time...
What do you mean engine sounds like I am in neutral? Does engine rev up but it sounds like you pulled on the clutch lever? Then it is most likely a clutch problem and a bunch of people already wrote good answers. If there is no engine noise and the problem occurs only when accelerating than there might be an issue with the air or the fuel. You should check online for known issues of your bike. One similar case that I heard was one Chinese made bike was engineered so poorly that when you turn on the throttle one of the air tubes made out of plastic would collapse due to low internal pressure and choke the engine. Then bike slows down, pressure normalizes and everything turns back to normal. Now, given that we are talking about a Harley, I wouldn't be surprised there is a similar engineering mistake. But if there is one, you will find other people with the same problem online. So what I suggest is that you first check to see if it is the clutch. To do so, you can go to a safe, preferably close to traffic space and accelerate hard. When the problem you described occur, try to listen to the engine if there is still a kick? Does the engine vibrate? If so it is probably the clutch. If your engine dies when this occurs then it is probably and issue with fuelling or air.
So you mean that when you add throttle, the revs go up but you don't accelerate? That sounds like either your clutch cable is adjusted wrong or the clutch itself might be worn out. I would try to adjust your clutch cable first and if that doesn't work, I'm afraid you might have to replace your clutch. If you're not comfortable with doing that, you could always take the bike to a shop and let them have a look at it.