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XJ 750 Seca Brake Bleed

Discussion in 'XJ Technical Chat' started by Manny Mercado, Jun 30, 2019.

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  1. Manny Mercado

    Manny Mercado New Member

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    Hi All,

    First time motorcycle owner here, frustrated and lost. I've spent the last 2 weeks trying to figure out this retched brake bleed, and still can't wrap my head around it. I rebuilt the front calipers with new seals and new stainless steel braided lines. I read through the forums and tried all the steps mentioned (normal bleed, reverse bleed, left it overnight with the brake lever engaged) and still can't get pressure to build.

    I know the anti-dive (AD) system isn't the issue (can feed fluid from the caliper bleeder through to the AD); I can push fluid from the caliper up to the reservoir until it spills over. Once I close the reservoir and try to build pressure with the brake lever, nothing!

    The previous owner did a master cylinder rebuild, and I can attest to the system working before I took it apart because I drove the motorcycle a bit to ensure everything was in working order.

    Any advice on what to do next? pull the master cylinder and reservoir and check through?

    Thanks
     
  2. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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  3. ManBot13

    ManBot13 Well-Known Member

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    Since the Seca 750 master cylinder is oriented vertically behind the headlight, and the reservoir feeds the bottom, you can get air at the high point where the steel line connects.

    It's messy so get lots of towels in there, but try to bleed the steel hard line. Pump the lever, hold, and crack open the fitting. Close and repeat a couple times.
     
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  4. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    I've never had to bleed it there on the Seca 750, but any master cylinder can get air trapped at the inital feed to the brake line. The main reason why I switched to vibrating the air out was to avoid the cleanup associated with what is essentially an on-bike bench-bleed. Particularly since you have to remove the headlight bucket to get good access to it. Not a problem when rebuilding the master, but a real hassle otherwise.
     
    Last edited: Jul 1, 2019
  5. Manny Mercado

    Manny Mercado New Member

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    Thanks for the quick reply! I have brand new steel braided lines from XJ4Ever, based on that same post about old lines corroding from the inside. Also followed your step-by-step instructions, without the sander step (don't have one, but figured once I got to the final steps I could McGyver something similar)

    I'll have to try bleeding the bent steel line next and see if that helps.
     
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  6. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    The big air trap is the calipers (ironically right next to the drilling for the bleed screw). Bleeding at the master shoudl help. but go ahead and give the system a going over with a wrench or screwdriver handle to be sure that all the air has a chance to bet stuck at the hightest point possible.
     
  7. Timbox

    Timbox Well-Known Member

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    Manny,

    Welcome to the site! Yes bleeding lines is a hit or miss sometimes. Just take your time and get a rhythm going with the MC and the bleed screw. Some reverse bleed with a syringe others use a vacuum bleeder to do this. Hitting the lines with a wrench or other item sometimes brakes up the air bubbles and allows them to be moved.

    One my Seca, I tied the lever to the bar and just let the fluid run into the lines until it started to drip out the bottom bleeder. As you can't see the fluid in the MC I took a small piece of hose and used that to fill and kinda measure how much fluid I was putting into the MC. I had issues with the fork system so just bypassed by removing those little hoses on the bottom.

    I don't know if you are new to riding as well? I see this is your first bike so just wanted to make sure you you do a really good check of the bike and make sure it is road safe. If you have not taken a MSF class please find one in your area and take the time. https://www.msf-usa.org/
     
  8. Manny Mercado

    Manny Mercado New Member

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    Hi Timbox, thanks for the advice! I have taken the MSF course (3 day weekend) a few weeks back, fully licensed now. I'm going over the brakes first before I ride it, have already gone through the electrical system to make sure it won't leave me stranded.
     
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  9. Manny Mercado

    Manny Mercado New Member

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    got it fixed! worked the issue up through the splitter (no isssues there) and the bent steel pipe (no issues there) to the MC and reservoir. Seems that something was either blocking or preventing the plunger in the MC from pulling brake fluid from the reservoir. Once I isolated the MC and reservoir to ensure it was drawing from the reservoir and pushing out fluid, it worked!

    Got the rear drum brakes done as well, that was much much easier.

    Thanks for the help all!
     
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