Stuttering with PMDC bike

[nedfunnell]

Hey y'all, I am experiencing an issue with my bike that I want to see if anyone might know about. I have very rough power delivery when applying throttle. It previously was very smooth and linear, but now it's very choppy.

My setup:
ME0709 (updated brushes)
Alltrax AXE7234
Domino throttle
22s Leaf cells

I experience it more at partial throttle, under 55mph- but it may just be smoothing out with greater intertia at that point, or when the controller is at 100% duty cycle. I plan to get into it later this week and see if there is anything obvious like loose connections, but I would appreciate any tips on things to look for.

I am slightly suspicious of the Domino throttle. I am going to try and find an old analog multimeter so I can see how smooth the resistance sweep is from 0-100%.

[nedfunnell]

Update: Got into the bike today to see what I could see and check balance. All high-current connections look and feel OK with no signs of heating/arcing. I also grabbed an analog multimeter to do a check on the throttle- and I think I do see a bit of 'flutter' at the lower end of the range, which would add up with my observation. I'm hoping somebody else with a Domino that's having no problems could repeat the test and see if things look similar, or different.

[Nicman]

I have a similar setup, magura throttle, 22nissan leaf cells, ~92v max. with a AXE7240 controller.
I think mine was my gear ratio though.

I am setup with a 13t with a 65t rear sprocket and at about 40mph (50percent max speed) the bike is sensitive to any more throttle input. (Jerky and sputtery response).

Sent from my SM-G955U using Tapatalk

[Stevo]

I have (had) the same setup Nicman has and never experienced issues like you described. Sounds like a loose ground somewhere ??

How many miles on the motor? Could it be time for new brushes?

[nedfunnell]

OK folks, I think I was able to diagnose the issue; I am pretty sure it's the throttle. I hot glued a 5k potentiometer onto a cut-off brake handle from a kids' bike and took a spin around some quiet streets. (Careful! No spring return!) I also found out the hard way that high-pedal disable is NOT enabled on my AXE7234- good thing I was prepared by holding the brake hard when I turned the bike on.

IMG_20180628_192025507_HDR.jpg

It rode just fine around my neighborhood, and I was able to repeatedly get results with my BarbieThrottle(TM) that I couldn't get with my Domino. It used to be quasi-impossible to ride 35mph peacefully, because at that throttle position (voltage control), the bike would lag and surge. It was smooth with the improvised throttle. The only other factor in the equation is the wiring between the Domino and the controller, since I wired directly to the controller for this test. I'll test that for continuity later while jiggling things around to see if anything might be funky there. If not- new throttle time. Too bad! I'd hoped a $90 throttle would last more than 3 years and a few thousand miles, but it looks like not.

[Stevo]

Maybe Magura throttles aren't so bad after all! Bummer to hear about the Domino but glad you got it sorted out pretty easily. Could have been a real head scratcher!