Front brake issues

[priebe]

Problem: Spongy and unpredictable front brake lever. Can pull the lever quickly (emergency braking) and get almost instant pressure (feel) without much lever movement. Pull lightly (trail braking or slow-stop braking) and lever can almost touch the handgrip before gaining enough pressure.

Background: I installed the Siegler braided brake line kit on my 2019 900 GT along with EBC-HH pads. I did the initial flush using Brembo DOT 4 fluid (ordered from Amazon). I connected a vacuum pump to the furthest caliper from the master and pulled a ton of fluid until I had built enough feel in the lever to take a ride. Found a gravel parking lot and did several runs to activate the ABS pump. Came home and pulled more fluid through the system. Still not happy with the lever feel. I disconnected the calipers, pushed the pistons back and elevated them above the master cylinder overnight hoping to get any last air from the system. This made no improvement. Thought it was possibly bad brake fluid, so I pulled almost a whole quart of fresh Valvoline fluid through the system. Still have the same issue. Ordered a master cylinder rebuild kit from the local Yamaha dealer, they ordered me an All Balls Racing rebuild kit. Turned out they ordered a kit for the regular Tracer 900, not the GT. Didn’t know there was a difference. Called the dealer and the 900 GT kit is unobtanium. I was able to use a few pieces from the 900 kit (one seal, spring, retaining clips) but it did not have the piston with new seal installed. I guess they press fit the piston together with that seal in place? I’m in a real pickle here and don’t know if a dealer will help other than to activate the ABS using their computer and do yet another flush. At this point I’ve pulled almost two full quarts of fluid through this bike. Do you think there is still air in the ABS pump?

[TomTracer]

16 minutes ago, priebe said:

Problem: Spongy and unpredictable front brake lever. Can pull the lever quickly (emergency braking) and get almost instant pressure (feel) without much lever movement. Pull lightly (trail braking or slow-stop braking) and lever can almost touch the handgrip before gaining enough pressure.

Background: I installed the Siegler braided brake line kit on my 2019 900 GT along with EBC-HH pads. I did the initial flush using Brembo DOT 4 fluid (ordered from Amazon). I connected a vacuum pump to the furthest caliper from the master and pulled a ton of fluid until I had built enough feel in the lever to take a ride. Found a gravel parking lot and did several runs to activate the ABS pump. Came home and pulled more fluid through the system. Still not happy with the lever feel. I disconnected the calipers, pushed the pistons back and elevated them above the master cylinder overnight hoping to get any last air from the system. This made no improvement. Thought it was possibly bad brake fluid, so I pulled almost a whole quart of fresh Valvoline fluid through the system. Still have the same issue. Ordered a master cylinder rebuild kit from the local Yamaha dealer, they ordered me an All Balls Racing rebuild kit. Turned out they ordered a kit for the regular Tracer 900, not the GT. Didn’t know there was a difference. Called the dealer and the 900 GT kit is unobtanium. I was able to use a few pieces from the 900 kit (one seal, spring, retaining clips) but it did not have the piston with new seal installed. I guess they press fit the piston together with that seal in place? I’m in a real pickle here and don’t know if a dealer will help other than to activate the ABS using their computer and do yet another flush. At this point I’ve pulled almost two full quarts of fluid through this bike. Do you think there is still air in the ABS pump?

Sounds like it to me. You've run much more fluid thru the system than it should take. Sure your method is correct?

[Lone Wolf]

27 minutes ago, priebe said:

I disconnected the calipers, pushed the pistons back and elevated them above the master cylinder overnight hoping to get any last air from the system. This made no improvement. 

Placing these banjo bolts with bleeder has helped me on various bikes, placed where top hose meets master cylinder or anywhere you want to bleed. Spiegler.

[TomTracer]

I have strapped the brake or foot lever (compressed) tightly overnight on a couple of bikes. Next morning nice and firm.

[bwringer]

From the description, it sounds like you only pulled fluid through one caliper?

[priebe]

2 hours ago, TomTracer said:

I have strapped the brake or foot lever (compressed) tightly overnight on a couple of bikes. Next morning nice and firm.

Thanks Tom. I have also tried this trick multiple times without any improvement.

 

1 hour ago, bwringer said:

From the description, it sounds like you only pulled fluid through one caliper?

To clarify, I pulled fluid from the right hand caliper first and then from the left hand caliper. Per the service manual, they say to start at the caliper furthest from the mast cylinder at the end of the brake line(s). Since the brake line hits the left caliper first then over to the right, I started my bleed with the right caliper.

2 hours ago, Lone Wolf said:

Placing these banjo bolts with bleeder has helped me on various bikes, placed where top hose meets master cylinder or anywhere you want to bleed. Spiegler.

This looks very interesting. Any idea what size the master banjo bolt is? Thanks for sharing.

Edited June 28, 2023 by priebe

[Lone Wolf]

1 hour ago, priebe said:

Any idea what size the master banjo bolt is?

My best guess is M10 x 1.25

That is the size I put on a Honda a few years ago, Revzilla says that is the size for Japanese bikes.

Revzilla is out of stock, but Spiegler has them. Partzilla does not specify the size of that banjo bolt, but they list it for a ton of Yamaha motorcycles, same part number Yamaha 90401-10172-00 BOLT, UNION

Edited June 28, 2023 by Lone Wolf

[2and3cylinders]

Did you get the Spiegler 5 line Kit, aka the racing kit; Or the OEM replacement kit?

If the latter, could there be an air leak where the flex lines connect to the OEM rigid pipes?

Does your vacuum pump have a gauge, if so, when you pump it down at each caliper, does it hold the vacuum?

Could one or both of the calipers be the issue.

Why is the GT kit unavailable and how many lines does it have; and why would it be different than the non GT?

[roadrash83]

When I installed the Spiegler lines on my 19GT, I was not happy with lever feel after vac pump bleed. I shoot the lock off my wallet which I don't like to do. I had the dealer bleed them hooked up to the computer and that did the trick. The dealer is able run the ABS pump and it gets all the air out and fully flushes the ABS system. They said they went through 3 bottles of Yamaha brake fluid in the process.

[RaYzerman]

Now that you have the system full with the vac bleeder, put it away and bleed the traditional way...

[priebe]

16 hours ago, roadrash83 said:

When I installed the Spiegler lines on my 19GT, I was not happy with lever feel after vac pump bleed. I shoot the lock off my wallet which I don't like to do. I had the dealer bleed them hooked up to the computer and that did the trick. The dealer is able run the ABS pump and it gets all the air out and fully flushes the ABS system. They said they went through 3 bottles of Yamaha brake fluid in the process.

Yup, already talking with a local dealer to have them extract some money from my wallet along with the some air likely stuck in the ABS pump. Stay tuned.

[priebe]

Update, had the local dealer do a "by the book" ABS pump air purge. It made zero change to the lever feel but did purge $150 from my wallet.  I was able to get my hands on an official Yamaha branded rebuilt kit for the regular Tracer 900 (non GT) and popped that into my GT master cylinder. If I was at 80% brake feel/confidence before, it went to maybe 84%. Not much improvement. Talking with some old time wrench benders, they suggest eliminating braking components and checking feel as I work my way. Either starting at the master and working to calipers or calipers to master. Example; remove the master cylinder bajo bolt and replace it with a regular M10x125 bolt and and check lever feel to see if it's the master? If not the master, then remove the first section of line at the ABS pump and plug it, check lever feel, and see if it's that section of line causing the issue, etc. continuing down the line. Seems like that's my only option at this point. FYI, I'm still riding the bike, and often at a spirited pace. Most times I work enough distance into my stops to figure out how the brakes are going to react in that instance to not be a problem. Just waiting for that true emergency braking scenario where you'll end up reading about me in the papers.