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[mattmccutchen]

My 2012 Zero S recently developed a problem: it is accelerating much more slowly than normal in each mode (Eco and Sport), even when fully charged.  I had left it parked outside, and one time when I passed by, I noticed the tailbag had been opened and all the contents had been put on the ground; the next time I rode the motorcycle after that, I noticed the slow acceleration.  So my theory is that the same person searched the tailbag and tampered with the motorcycle in a failed attempt to steal it, causing the acceleration problem.  I further suspected the throttle or kill switch cable might be kinked (that happened to me a few years ago), but I wiggled the wires and it was unclear if it helped.

Normally I'd go to a Zero dealer for service, but the nearest dealer is about 200 miles away and shipping the motorcycle alone will cost about $600, so I'm hoping to repair the motorcycle myself.  I have no experience with this, but the MIT Electric Vehicle Team will let me use their shop and tools and may guide me through some of the steps.  Can someone summarize the steps I should take to diagnose and (if possible) fix the problem and point me to any documentation I'll need?

I suspect it may be obvious to many people in this community how to find this kind of information, but I'm struggling and would really appreciate some help.  I found a thread about a similar problem caused by the throttle, but if I'm going to test the throttle resistance, I need to know what's normal.  I also saw a thread about some diagnostic interfaces, but it's unclear to me from that thread which one I should use and where the port is on the motorcycle.  I'm guessing Zero headquarters won't be willing to help me, but I can ask if you think it's worth asking.

Thanks!

[Cortezdtv]

Can anyone confirm if the 2012s have a fuses like the 13's? I just dont know for the S platforms... But
It sounds like One of the sand filled fuses

Kinda  like the lower power fuse particularly may be poped if you WOT will it cut out during acceleration?

[protomech]

The 2012 bikes have a low-voltage fuse cluster underneath the front black trim panel (just in front of the seat) and a high-voltage fuse cluster mounted in the top rear of the battery monolith. Certainly worth checking both fuse clusters.

Does the throttle have a full range of torque control, or does it reach maximum torque with a very small amount of twist?

Does Eco vs Sport make a difference (in terms of maximum torque or how quickly it is reached, per the above)?

Are any warning indicators lit on the bike?

[centra12]

Hello

Have you the status of the Sevcon Controller LED checked?

[Richard230]

Hello Matt.  Nice to hear from you again.  I hope you are doing well at MIT.  Before you dive into the electronics, I would check to be sure that there is nothing dragging on the chassis and that the bike, when pushed with the motor off, is no harder to push than it was before you started having the problem.  It is possible that a brake pad is dragging or something else is interfering with the wheel rotation. Sometimes a brake pad piston will not retract into the caliper, resulting in drag on the brake disc.  If that has happened then you will likely need a new set of pads (as they may be glazed by now) and the caliper and its piston, along with the sliding pins, will have to be carefully cleaned and all corrosion removed.

[mattmccutchen]

Thanks for the ideas.  My forum notification settings were wrong, so I didn't notice anyone had replied until yesterday, and this morning was the first convenient time to do any tests.  Diagnostic results so far:

• I took out and inspected all the fuses, and nothing looked obviously wrong, but I didn't have the tools to test them for conductivity.  I can do that later at the MIT EVT shop.
• The acceleration does increase over the entire throttle range, and Eco or Sport mode does make a difference.  In 12 seconds, with the throttle open all the way, the motorcycle reaches 20 mph in Sport mode or 14 mph in Eco mode.  With the throttle open halfway, it reaches 7 mph in Sport mode or 3 mph in Eco mode.  (These numbers may be off as much as 20%, but I think the point is clear.)
• No warning lights are lit on the dashboard.
• I couldn't find the controller LED.  It looks like the entire controller is covered.  I may be able to do this at the shop.
• I pushed the motorcycle and I don't think it was harder than before, but I could remember wrong.  A better way to measure this might be to measure the deceleration rate, but I didn't think to do that and it's probably not useful unless I have a standard to compare to.

In a private message, another member said the throttle resistance should range from 0 to 5 kΩ.  I'm planning to go to the MIT EVT shop tomorrow when they are open, and that will be the first thing I test.

[Richard230]

Matt, if you can get the wheels off of the ground one at a time, try turning them by hand just to make sure that there is no binding of the brakes or wheel bearings.  And don't forget to check the air pressure in your tires.

[mattmccutchen]

I was able to test the throttle resistance today.  I followed the throttle cable to the zip tie on the left side of the motorcycle, released the zip tie with a pocketknife, and disconnected the connector just past the zip tie.  The side of the connector away from the throttle has four wires: orange, brown, blue, and white (cut off).  As expected, the side toward the throttle is missing the pin for the white wire.  I tested the resistance between each pair of pins as the throttle goes from fully closed to fully open (corrected 2016-01-25).  The results:

• Brown to blue: starts at 666 Ω, decreases slowly at first and then suddenly to zero.
• Orange to brown: starts at zero, increases to around 3000 Ω and then decreases to 666 Ω.
• Orange to blue: constant 666 Ω.

(I now realize I didn't pay attention to the polarity with which I connected the meter.)  Based on this, I should replace the throttle, right?

I found this thread about throttle models, and I'm assuming the options are the same for the 2012 Zero S, so the Magura throttle would be the exact replacement.  I might try the Domino throttle since it's supposed to be better, but how much more complicated is it to install?  Anything else I should know?

[chdfarl]

There was a guy on endless sphere selling the domino throttle for $40. Apparently he's gotten a few batches an is legit. If you Google endless sphere domino it should pop up.
It seems to me that your throttle craped out but double check by feeding 5v to the blue wire and the ground to the orange and the black/com/b- of a multimeter and the red/b+ to the brown. The meter should read 0v at rest and up to 5v at full throttle. Apparently that is the orientation that zero uses (I don't know,  haven't checked my xu's) so it wouldn't hurt to check it. My magura that I bought for a project does read both 0-5v and 0-5k ohms so yours should too.