Jerky PAS

[cem1965]

Hi can anyone tell me why my pedal assist is jerky when pedeling, it works fine on the throttle but on pedal assist is is very jerky (going on and off all the time). Thanks

[hemo]

PAS will normally produce an on/off signal every time a magnet passes the sensor though in normal use one won't feel the switching, unless one is pedalling at asilly slow cadence.
With a jerky/intermittent working PAS then one may need to turn the bike upside down or use a bike work stand.
Check the magnet disc is secured firmly to the BB axle, if said disc moves around the axle axis then it needs securing tightly so it only rotates when the cranks turn. If square taper BB and the splines on the magnet disc are broken/missing or ineffective at griping, try some amalgam tape on the BB axle and fit the magnet disc firmly on to said tape.
Check the gapping between the magnets and sensor head, ideally one is looking for approx. 1mm or less.
Ensure the sensor is firmly fixed in a stationary position.

[cem1965]

Thanks for your reply, but all the above are okay and the gap between the BB and sensor are at manufacturer measurements but I'm still getting jerky from motor when pedeling. Also everything is new including the motor and battery. Thanks

[stodd]

It could be the cable from the sensor, or the connection where that cable plugs into the controller. It's always difficult to check intermittent connection in a cable that has been snagged or stretched at some point.

[willcee]

Had same issue recently, with a REAR hub motor ex Orbea Gain 250W governed now by Bafang controller .. lent the machine to a friend while his was being refinished, he did a couple of runs on it without issue and it came back with throttle only as the problem, he explained so i had it up on the stand, and when pedalling slowly it seemed to only be picking up on one or two of the magnets which were sited underneath the bottom bracket tightened against and behind the hollowteck cups, , we removed the Ultegra chainset and checked each magnet which were bonded to the inside of the 36 ring, so knowing i had a spare which he himself had provided earlier in the year could we find it!!! i had another which was suitable and had the wrong plug for the higo wiring on the bafang stuff, so we cut and joined them soldered and worked out the correct wires to solder all 3 of them with only one colour constant, checked it on the net, and on here i think with Hemo, and it was back to working normally ..just in case of another problem i ordered one on Aliexpress which arrived 3 weeks later...i think it was water ingress....will

[hemo]

Which /what type of PAS set up, a pic says a lot. If a crank two piece PAS then what ever the maker say's, make sure the gap is as I mentioned.
One assumes ahub motor is in use ?

[fivebikes]

I had a similar issue with my first Swytch kit. Only using a pedal sensor, no throttle fitted. At start up the power delivery was jerky, but smoothed after a few revolutions. After a couple of emails, I did a video call with them and the tech person identified it as a faulty controller module, as the pedal sensor was behaving as it should and the gap was fine. At a guess I thought it was the hub motor but he said they are very reliable. Speedily sorted and not been an issue since. Don’t know what make system you’re using but I’d check all the connections, disconnecting/reconnecting, looking for bent pins, signs of contamination etc.