[Z1R rider]

I guess I'm curious how fast you were going and what gear you were in when you lost it. I would guess that the street you were riding on was dirty or gravely or wet if the rear end spun up and you went down. Or maybe because your a new rider it took off faster than your comfortable with and lack of skills took you down, could the problem be poor clutch accutation. A lot of us are self taught and a lot of us learned to ride in the dirt (on a dirt bike) before we ever rode on the street. Take your time and find a parking lot of some other open area to practice take offs and stopping without putting the extra pressure on yourself of holding up traffic or going down in traffic and possibly hitting someone or being hit by traffic.