2007 FJR1300 Rear Brake Issue - Yamaha FJR Forum : Yamaha FJR Owners Forums
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post #1 of 13 (permalink) Old 03-23-2020, 03:55 PM Thread Starter
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2007 FJR1300 Rear Brake Issue

I tested the rear ABS by locking the rear wheel at speed. The rear brake petal was solid for a bit, then lost brake pressure as the petal bottomed out while in motion. I released the rear brake petal and reapplied - it then had pressure as it should. When I came to a stop, the rear caliper had siezed. I took off the pads and rode home safety.

The rear caliper piston moved back once I released pressure in the brake lines. I thought it was the rear brake master cylinder causing the issue, so replaced the internals of that unit, then bled the entire brake fluid system (except the ABS reservoir). Fluid was being drawn down from the rear brake reservoir through the front right caliper, but no fluid was going to the rear caliper during the brake bleed process. Note that I also pumped the rear brake petal and could hear a swishing sound, but still no fluid in the rear caliper line.

Any suggestions on how to troubleshoot why brake fluid is not going to the rear caliper?

Thanks in advance.

John
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post #2 of 13 (permalink) Old 03-23-2020, 10:10 PM
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I could go on a rant here but I'll try to be calm. This is the classic failure of not flushing and bleeding and activating the ABS, especially on Gen1 and 2 bikes, mostly prior to '08. This should be done EVERY YEAR.
John, I'm assuming with one post you are new to the bike. Normally without ABS, the brake fluid circuit bypasses the ABS circuit and you brake normally. When you activate ABS, it forces fluid through the ABS circuit in the ABS pump. That ABS circuit has dried up fluid in it which acts like "cholesterol" in the arteries. You forced that partially hardened fluid now into the portion that goes to the rear line. Is it in the pump still or moved further, we don't know, but it is blocking the passage of fluid to the rear.
Here's a job likely to blow most of a day............

Hope and pray it moved out of the ABS pump... to help it move (big maybe) you should activate the ABS via the ABS diagnostic connector up by the front left of the battery. Harness available with a switch if you so wish, otherwise you can jumper the appropriate two wires at the ABS diagnostic connector. You will have to do this multiple times to see if you can get the blockage to move.
After that attempt, if no success, then trace the plumbing to what feeds the rear wheel. It goes through the metering block and proportioning valve, one of which may be blocked if the cholesterol made it that far. So, working upstream from the back wheel, loosen the first fitting (banjo or whatever) on the steel line and press the brake pedal to see if fluid is flowing at that point. Maybe it's just the rear line blocked? Move on to the metering valve, is there fluid there when you pump. Last point will be at the ABS pump itself, loosen that fitting and see if you have fluid flow there. Wherever you find fluid flowing, stop there and clean out the downstream plumbing with isopropyl alcohol, let it soak for a while. You'll have to hook the plumbing back up and try to get fluid moving......

If the blockage is still within the ABS pump, then I'm not sure you'll be able to fix it. Maybe with the rear line loosened/disconnected at the pump, activate the ABS again, hope the lack of backpressure will cause something to flow.
OK, all of this is going to be messy, rinse everything down with a spritz of isopropyl alcohol.
The only cure for a permanently blocked ABS pump is a replacement pump, and you have to hope you get a good used one. You don't have to replace it, just understand that ABS won't work on the back wheel.
However at the moment, fluid is not flowing to the back wheel, and that must be cured some way or another. Being that you're getting fluid flush at the right front caliper, that's a good sign, it MAY mean the ABS pump is not blocked, again, hope and pray it's just the rear line blocked. Do not ride the bike until you get the rear caliper bled.
Your rear caliper seized because (a) the blockage moved and didn't allow fluid to return, or (b) there was a lot of water content in your fluid, it may have turned to steam which pressurized the system, overpowering the rubber expansion baffle in the reservoir.


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Ray
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post #3 of 13 (permalink) Old 03-24-2020, 05:32 AM
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What Ray says every word of it ^^^^

He gets a bit passionate about replacing the fluid but he is correct and he means well.
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post #4 of 13 (permalink) Old 03-24-2020, 08:32 AM
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There have been a couple times where the bleed screw was blocked, too.

Russ
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post #5 of 13 (permalink) Old 03-24-2020, 08:34 AM
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I completely agree with Ray on his analysis & plan, but let me add a couple of things. Being that you said it had trapped pressure one other thing that can cause that is that the “spooge” hole in the rear master cylinder could be plugged, trapped pressure is common if this happens. The spooge hole is the tiny little hole in the master cylinder reservoir and you need a very fine wire to clear it. I’ll add that I believe Ray is spot on in his analysis of this but you need to check the spooge hole as well.

The other thing I’ll add is that with an abs equipped vehicle if you pump the pedal/lever while it is in abs mode usually it will deplete the trapped fluid that the abs is using to pulse the brakes and if you pump the pedal/lever you’ll end up with your pedal/lever fully down or against the bar and then you’re screwed. Just hold things steady, I don’t believe that is what happened here at all but this is just a personal deal that all abs suppliers should be teaching and don’t, this applies to your car/truck as well.

Again I think Ray is spot on in his analysis so go that way and definitely check the spooge hole as well.
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post #6 of 13 (permalink) Old 03-24-2020, 08:38 AM
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Agree with all that, and the plugged bleeder possibility... good stuff.

Ray
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post #7 of 13 (permalink) Old 03-24-2020, 10:38 AM
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Just out of curiosity. Has anyone, with a problem with the ABS pump, just ran lines from the front MC to both front calipers {splitting the right side to run a line to both sets of pistons OR just running two lines and leaving out the bottom set of piston on the right side}, and from the rear MC to the rear SC?

I know that in most cases when the ABS fails, the brakes work the same, just without the benefits of ABS. But in this case, if the owner finds the "cholesterol" prevents him from using the rear brake, isn't "bypassing the whole ABS system" an alternative?
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post #8 of 13 (permalink) Old 03-24-2020, 12:01 PM
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Quote:
Originally Posted by philharmonic View Post
Just out of curiosity. Has anyone, with a problem with the ABS pump, just ran lines from the front MC to both front calipers {splitting the right side to run a line to both sets of pistons OR just running two lines and leaving out the bottom set of piston on the right side}, and from the rear MC to the rear SC?

I know that in most cases when the ABS fails, the brakes work the same, just without the benefits of ABS. But in this case, if the owner finds the "cholesterol" prevents him from using the rear brake, isn't "bypassing the whole ABS system" an alternative?

Its been done on a gen 1 the guy just did not like ABS so he had pipework made to remove the valve block out of the equation. But he wasnt happy there and wanted to remove the valve block - no idea how he got on.

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post #9 of 13 (permalink) Old 03-24-2020, 02:39 PM Thread Starter
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RaYzerman, Et Al - Thanks for the responses. It was a used bike and was not well maintained when I got it.

Compressed air was observed to be flowing through all the banjo bolts, lines, bleeder screws, spooge hole in the rear master cylinder reservoir and proportioning valve in the rear brake system when I took everything apart. Will there still be a need to drop isopropoal alcohol through those lines if air is flowing through? It appears that the blockage is in the ABS block at this point.

I just ordered the ABS diagnostic connector to manually fire the ABS pump. Will let you know how everything goes later this week once the ABS pump test is complete.

Cheers,
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post #10 of 13 (permalink) Old 03-24-2020, 11:40 PM
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If good air is flowing, then no alcohol... it was only to dissolve the cholesterol wherever it may be.... run the ABS test a good half dozen times or more... hopefully it clears. I don't think anyone has attempted to clear an ABS block by stripping it down and soaking it... wonder if priming up the rear system with isopropanol, then running the test would do any good.. nuthin' to lose perhaps.....

Ray
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