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[NanoMech]

A friend of mine stepped off his bike as it started leaning over too far over while stopped on a hill. The motor accelerated and the wheel started spinning at moderate, and accelerating, speed. We flipped the kill switch, lifted it up, and it has been operating normally since then, around 3 months and 300 mi.

I believe the throttle is a potentiometer, and so there is no cable to pull. The throttle is on the right side, and that was the side facing up and not touching anything. The throttle has good return response. Anyone have a similar experience? Not an issue, more a curiosity on how it could occur.

[Burton]

I dropped my bike one morning on a ramp to a garage which was covered in snow going 1 mph ... when it fell throttle side up the wheel also started to spin a lot ... but the bike shut itself down I think. I hit my emergency kill switch anyway though.

[trikester]

If you are talking about a 2010 or 2011 those motors are series wound DC motors. A series wound motor can spin itself up to the point of destruction when powered without a load taking very little power to do so. Those bikes take very little voltage from the throttle pot to spin up to high rpm when the wheel is off the ground. My guess is that there was just enough residual voltage with the throttle closed to do that.

The Zero bikes from 2012 & up use 3 phase AC motors and will not show that characteristic.

Trikester

[m0t0-ryder]

The throttles on all the Zero models are Magura 0-5K ohm potentiometers.
Different years had different pinouts with 2 or 3 leads being used. some connectors had 4 pins but only 2 or 3 will be used (depending on the model year).
To test you can unplug the throttle connector and measure between two of the leads in there.
You should read 0-30 ohms when closed with a linear rise to (about) 5000 ohms at wide open throttle.

Again... you should see a linear rise from very little resistance to about 5000 ohms. Any jumps in resistance (up or down) while rolling the throttle on indicates a faulty throttle.

Note: Digital Multimeters (DMM's) will appear to jump as they autorange through the resistance ranges. An analog VOM gives a much better indication.

[NanoMech]

If you are talking about a 2010 or 2011 those motors are series wound DC motors. A series wound motor can spin itself up to the point of destruction when powered without a load taking very little power to do so. Those bikes take very little voltage from the throttle pot to spin up to high rpm when the wheel is off the ground. My guess is that there was just enough residual voltage with the throttle closed to do that.

The Zero bikes from 2012 & up use 3 phase AC motors and will not show that characteristic.

Trikester

The bike was a 2014 DS with very low mileage. I've experienced throttle run-up on gasoline bikes, when the carb flooded or if the throttle cable, a real wire cable, was snagged on some part of the bike or bushes. I'll ask him to place his bike on a stand and learn if there is just enough potentiometer voltage to spin the wheel. I'm not worried about it, just curious, as mentioned. Seems it is not a rare event and the bike runs well.

[teddillard]

If you are talking about a 2010 or 2011 those motors are series wound DC motors.

wuuut?  Didn't those bike run Agni?  ...ie, PMDC?   Then Motenergy, etc.  I don't remember any Zero running a series DC motor, ever. 

[trikester]

My 2010 DS was a series wound motor, no permanent magnets.

One thing I liked about it was hill climbing. You didn't have to change the throttle setting when coming to a hill, it was like a Diesel.

Trikester

[teddillard]

huh.  These guys say it's an Agni: http://www.motorcycle.com/manufacturer/2010-zero-ds-review-90186.html
...and these guys say "brushed permanent magnet": http://www.topspeed.com/motorcycles/motorcycle-reviews/zero-motorcycles/2010-zero-ds-ar87355.html ('course they also call it an "engine" lol.)

...as do these guys: http://www.motorcycle-usa.com/25949/Buyers-Guide-Specifications/2010-Zero-DS.aspx

Even the '09 S shows a PMDC motor on wikipedia: http://en.wikipedia.org/wiki/Zero_S

NOT trying to be a dick, (and sorry if it's off-topic) but if they were running a series-wound motor that would be a major deal IMO.  The only guys I know running series DC are the drag-racing guys. 

[trikester]

I never saw an unloaded PM motor that would wind up until one thought it would explode with the throttle just barely moved off the bottom. If I took the wheel off the ground that is exactly what it would do. I could not run it safely without dragging the rear brake to put some load on the motor. It was also difficult to control speed on slightly undulating road. When looking at the motor it looked like a series wound motor (heavy gauge field windings). I have no idea who made the motor.

I've had experience with series motors, shunt motors, and PM motors and that one had all of the characteristics of series wound. Of course it's possible that the controller had the characteristic of increasing output voltage as the load current dropped thus simulating a series wound.

Too bad I no longer have that bike.

I got one of the first 2010 DS' and I wonder if it had a different motor. Somewhere I read that the motors in those bikes were series wound.

Trikester

[nigezero]

The other day i rode up my driveway and when i closed the throttle the bike continued to drive just slightly. In my case this was because the throttle body was a bit gungy and was sticking on a bit; i love right near the beach so corrosion and build up is chronic. Needed a clean and lube. Maybe it was justa  sticking grip like mine?

[teddillard]

I can't say enough about the Domino throttle.  https://evmc2.wordpress.com/2014/03/30/5k-ohm-throttles-domino-vs-magura/

Simple swap-out, totally sealed.  (IP67 specs)

...but yeah, something sticking in the throttle or some connection that's getting shorted out, or a wire that's getting pinched...  pretty much the only answer that makes any sense to me.  Or, you know, gas in the floats.