Front Brake Rotors/Wheel Knocking Back Caliper Pistons/Pads?

[2and3cylinders]

I've had the following issue occur approximately a dozen or more times total now on different rides on my 2015 FJ-09 which I purchased new in late June 2016 and which now has less than 4,000 miles on the odometer.
 
After running down the road without touching the front brake lever for a appreciable distance / time, when I pull back on the front brake lever it moves back with much more travel the normal with low pressure resistance and without causing the front brake caliper pistons to move toward the brake pads and engage the brake rotors.
 
This is of course very disconcerting to say the least!
 
When this occurs I then immediately release the brake lever and pull it again and the front brake system instantly builds adequate pressure and functions normally; i.e., with short lever travel and a wooden feeling that is more difficult to modulate than I'd prefer but normal according to most of the reviews I've read and seen on the FJ-09.
 
When this problem first occurred in late July 2016, when I got back to my full equipped shop, I immediately put it on its centerstand and jacked up under the oil pan (automobile scissor jack with plywood spacer) to raise the front wheel off the floor.  I then carefully measured both front rotors lateral runout as well as the front wheels lateral runout with my very rigid and accurate dial indicator set-up. To my surprise, both the front rotor's and front wheel's runout were within the tolerances prescribed in the factory shop manual (which are actually tighter than permitted on my Honda); although the wheel's runout was closer to the limit than the rotors were.
 
Due to this apparent issue with the front brake system, I now consciously keep track of how long its been since I pulled the front brake lever while riding and almost automatically squeeze the lever twice quickly to ensure the front brake caliper pistons and pads servo into the rotors and diminish my road speed and slow my forward momentum and travel as road conditions dictate.  Servoing the front brakes however does not provide the smoothest and most controllable braking, and quite frankly is a ride-around technique I should not need to do.
 
I dread even talking to my Yamaha dealer and even more so the hassle of taking the bike in and leaving it in their hands, as I always do all my own maintenance and repairs because I do not trust anyone else to do so.  However, as this front braking problem may be a warranty claim issue, I may have to take it into the dealer, which means finding someone to pick me up and take me back there when hopefully the dealer has completed the necessary corrective work (which I'm very concerned they may not do in their first attempt and maybe not even their second, and they are reportedly the best Yamaha dealer service wise in the Chicago metropolitan area).
 
Do you think bleeding the brakes will resolve the issue?  I don't think so but would will be willing to try bleeding the front (and the rear as long as I'm opening a fresh bottle of DOT 4) brakes first before taking it to the dealer.
 
Opinions ya'll?
 
 
 

[DavidS]

I would try bleeding the brakes first, the behavior you describe sounds like either low fluid or air in the system. Does happen regularly?

[skipperT]

Based on the info you've provided, it certainly sounds as if you've checked everything else.
 
I'd bleed the front brakes.
 
However; first I'd recommend carefully removing the cap on the master cyl and GENTLY (or you will spill fluid from the return port- have rags handy) squeeze the front brake lever slowly and check for trapped air in the piston of the master cyl.
 
You may see some very tiny bubbles when you gently squeeze the lever. If so, you may not even need to bleed the front brakes once the air is removed from the m.cyl.
 
If you don't perform the above procedure, and there's no air trapped in the front brake lines - then bleeding the front brakes won't show you any improvement - because you may still have air trapped in the master cyl.
 
I hope this makes sense - I'm still on my first cup of coffee. Good luck.
 
Skip

[2and3cylinders]

Flushed and bled brakes thoroughly.
 
Left front bleed nipple sucked air past threads so removed and wrapped with yellow Teflon thread seal tape. Right front bleed screw had an O-ring; first time I've seen that, must be ABS related.
 
2016-09-07 Update:
 
No servo pumping required in 600 miles afterward but still very short lever travel and IMO elevated pressure required even more pronounced as since new. Is that the norm for everyone???
 
ABS light did go on an flashed after 150 miles? Turned off and on and light went out and did not return. What?
 

[lhancock]

I was chasing the very same problem when I first took delivery of my bike. It turned out the front axel was backed out and allowing the wheel to move left and right during hard turns. Photos in link below
 
http://fj-09.org/thread/2656/mindful-delivery-new-bikes

[2and3cylinders]

2016-11-21 Update:
 
Still no brake lever "fade" but occasionally the ABS warning light goes on for no apparent reason (and I keep the sensors clean given my units history for this happening). Turning the ignition completely off and immediately back on and starting the engine causes the light to go out as normal and prescribed shortly after restarting. Any one else with this occurring??