Front wheel hop when braking - suspension arm bushes, or... ?? Any help?

[Jetfixer]

I'm working on a friends 2023 RTL that has a severe wheel hop when doing moderate to hard braking. Both front wheels visibly hop very rapidly as if the brakes were grabbing and releasing very rapidly. Here's a list of what I've done and/or checked...

Spyder bought new by current owner. Has 23000 miles.
Two like new Vredestein tires, Centramatic balancers. Both tires running at 18 psi.
Brake pads and rotors are good with no excess runout. Absolutely no pedal pulsation when braking. No binding or pulling. No air in brakes.
No excess play in steering system.
Laser aligned to 3/16" toe-in over the specified 124 inch spread. (Service manual allows between 0 and 5/8").
No shaking in handlebars during the wheel hop. (It just looks like it could throw the fenders off).
No ball joint or tie rod joint wear found.
No wheel bearing play. Wheels mounted properly and nuts torqued to 77 lb/ft.
Spyder still has original anti-sway bar and heim joints. No play or looseness in any of these parts or mounting.
The bike rides very smoothly, does not pull or drift. The problem is only during braking.

I'm beginning to suspect it's the suspension arm bushings. I'd appreciate any help anyone can offer. If I've left something off this list let me know. I've more than likely checked it!

 

[BajaRon]

It's the wheel hop that has me scratching my head. Pulsating, etc., could be warped rotors, worn A-Arm bushings, etc. But for wheel hop, I would remove the Centramatic balancers, torque the front wheels correctly in 2 stages, and give that a try. We've had some wierd front end issues go away by removing the Centramatic balancers.

Check tire pressures while you're at it.

A bit of a shot in the dark. But not hard to do and virtually free.

 

[mecsw500]

I would immediately suspect a problem with the ABS system kicking in, or out, when it shouldn't.

I'd get the dealer to flush the brake fluid AND flush the ABS unit, using the BUDS system. I'd have them check the ABS sensors and rings on the wheels, at the very least clean them or test them for correct signal pulses when the bike is in gear and moving down the road.

Incorrect signals from any of the wheel sensors or contaminants in the brake fluid in the ABS module could be causing issues. Even a faulty ABS module or ECU could be an issue.

Check the connectors from the ABS module to the ECU for corrosion, the same for all three wheel sensors to the ECU harness. Once you have cleaned them all out with electrical connector cleaner and a tooth brush apply a little dielectric grease before re-connection.

I would seriously get the dealer to look at it as the BUDS system will be able to test the sensor operations and allow a full brake fluid change including the ABS unit as well as just the regular parts of the brake lines.

As the Nanny control system relies heavily on correct ABS function, I would treat the issue seriously as you don't want that part of the bikes automatic systems to go wrong when you most need them.