Why would a bike try to move forward when it's in neutral and you give it a bit of throttle?

I was looking at a used Harley, and when the guy started it, in neutral, it sort of moved forward when he revved it.

 

Clutch plates are still stuck together. Hopefully after it warms up a bit that won't happen. You'll probably notice a louder clunk when it goes into first gear for the first time for the same reason. This is why I always start my bike in neutral *and* with the clutch lever pulled in. Less strain on the starting system.

 

drag on the clutch plates I'm guessing.

 

I knew there had to be an easy answer. Thank you.

 

Improperly adjusted clutch, something broken/dragging in the clutch pack, wrong fluid in the primary, one of those "easy clutch" adapters, problem with the release mechanism. I'm sure there's more reasons.

 

All good and valid points. I just spit out the first thing that came to mind.

 

Guys, if the bike is in neutral you can let the clutch out and the bike shouldn't move!!! Chances are the tranny lube is a little thick and the lube is trying to turn the gears. It shouldn't do it once it's warm. Of course you could also have some bearings getting a little "Tight" and dragging!!
John

 

I didn't see the neutral part. I'm sorry, my bad reading comprehension. I was thinking moving forward with the clutch in while in gear.

I'm with John.

 

It saw your Japper and was trying to escape......