Fly 7 scooter alarming loud clunk in rear end while riding

[Zambam]

With 6500 km this hasn’t happened till a week ago. This single clunk is loud and can be felt. The faster I am riding, the stronger the clunk. I thought it was the center stand dropping or something but after throughly checking it, not the center stand. Two days ago, I felt a slight clunk from starting off from a light then it would’t move. Recycled power with key switch many times after which it moved and rode home.

Things tried so far:
Checked / tightened axle and suspension nuts and they were all fine.

I then suspect something with the motor. Putting bike on center stand engaging throttle, wheel spins quietly with no noise or drag from brakes.

Next I suspect something with the controller or something with the 3 phases losing sync momentarily.

I happen to have another controller with 30 miles when the speedo function failed (I damaged it poking around in the cockpit trying to find battery B+ to hook up a volt meter.).

Swapped controller and rode approx 8 miles so far with no speedo or odo w/o any clunks so far. Will test ride more and see what developes.

Based on the above, what do you think failed? The contoller is under the seat, well protected from the elements. The phase and hall sensor connector had no corrosion, non of the wires showed any fraying. The connector was reseated when I swapped controller but I don’t think it was a phase connector contact issue.

 

[E-HP]

With 6500 km this hasn’t happened till a week ago. This single clunk is loud and can be felt. The faster I am riding, the stronger the clunk. I thought it was the center stand dropping or something but after throughly checking it, not the center stand. Two days ago, I felt a slight clunk from starting off from a light then it would’t move. Recycled power with key switch many times after which it moved and rode home.

Things tried so far:
Checked / tightened axle and suspension nuts and they were all fine.

I then suspect something with the motor. Putting bike on center stand engaging throttle, wheel spins quietly with no noise or drag from brakes.

Next I suspect something with the controller or something with the 3 phases losing sync momentarily.

I happen to have another controller with 30 miles when the speedo function failed (I damaged it poking around in the cockpit trying to find battery B+ to hook up a volt meter.).

Swapped controller and rode approx 8 miles so far with no speedo or odo w/o any clunks so far. Will test ride more and see what developes.

Based on the above, what do you think failed? The contoller is under the seat, well protected from the elements. The phase and hall sensor connector had no corrosion, non of the wires showed any fraying. The connector was reseated when I swapped controller but I don’t think it was a phase connector contact issue.

View attachment 389938

If swapping the controller out “fixed” the issue, except for the speedo, it would be hard to conclude that it’s not controller related. Although the controller is protected from the elements, is there still ample air flow to keep it from, overheating? Seems like you need to ride more miles before settling on the controller as the issue though.

 

[Zambam]

If swapping the controller out “fixed” the issue, except for the speedo, it would be hard to conclude that it’s not controller related. Although the controller is protected from the elements, is there still ample air flow to keep it from, overheating? Seems like you need to ride more miles before settling on the controller as the issue though.

Agree that I should put on more miles before making any conclusions. Good point about possibility of controller overheating. The controller is not in a closed box but not in open air either. It is bolted to a steel surface which provide some cooling via conduction, I do full throttle it to get a jump on cars from stop lights often, drawing 2.5 kw per JBD BMS, but only for 2 to 3 seconds, then cruise at NYC street speed limits of 25 mph.

Now that you mention possible overheating of the controller, I will instrument it with a thermocouple bead and see if it's a problem.

 

[Zambam]

It was pretty easy to mount the thermocouple bead under the head of the controller mount screw.

You can see some daylight (to the ground) in this pic so there is some air flow.

 

[E-HP]

Great. More data is better than guessing!

 

[Zambam]

Approx 10 to 15 miles has been ridden so far with no clunk. How many more miles do you think before I can say it's the controller?

It was around 88 F during a 5 mile mile with a lot's full throttle (for 3 secs). Hottest temp measured was 140 F (60 C).
Are those acceptable temps given the location of the Thermocouple bead on the controller?

 

[Zambam]

Have around 25 miles so far on the controller (with no speedo/odo) and still no clunk from the motor. I am still wondering what's the mechanism that caused the clunk? Searches on ES found nothing similar.

Yesterday was very hot 99 F here. I used a strip of inner tube to tie the meter to a piece of foam wedged into the storage compartment. Much easier to read with meter in a horizontal position while riding, compared to laying the meter vertical in the compartment.

Later, the controller got up to146 F in the 5 mile ride home from some take out food.

 

[Zambam]

the controller got up to146 F

Found a good ES thread on controller temperature.