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XJ750 Seca Master Cylinder Bleeding

Discussion in 'XJ Technical Chat' started by ManBot13, Sep 25, 2009.

  1. ManBot13

    ManBot13 Well-Known Member

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    FOR XJ750 SECA OWNERS!
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    This post was almost one asking why I couldn't get ANY pressure in my newly rebuilt brake system (Braided Stainless steel lines , rebuilt caliper and MC, cleaned out antidive, all new parts from chacal).

    After putting it all back together, I used a mightyvac to pull fluid into the calipers and antidive units filled the reservoir (behind the headlight...a b**ch to get to even without the headlight mounted). I had read some posts about bench bleeding the master cylinder, and the mightyvac showed how, but of course the XJ750 Seca HAS to be "unique" (PITA).

    After ALMOST dismantling the MC again after removing it from the headlight bracket (and risking damaging the brand new seals I had just installed), I decided to try something. The steel brake line was still attached to the top of the master cylinder, so I tightened it down, put my finger over the other end and pumped the plunger. And I got pressure!

    Looking at the system, I realized that where the top of the steel brake line connects to the MC is the highest point on the system. Since the MC is vertical, all the air got trapped there, and there is no way for it to make it out. I bled it after reinstalling it on the bike and hooking all the lines up by pumping the brakes and holding, then loosening the brake line (have to loosen it 1/2 turn or more to get it to release) hearing air rush out, and tightening before releasing the handle. A few pumps like that and I got all air out and the pressure back.

    Word of caution, it was very messy...and there is alot of stuff back there. Guess that's the price we pay for owning the 750 seca...
     
    ManBot13, Sep 25, 2009
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  2. SQLGuy

    SQLGuy Well-Known Member

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    Thanks for the tip. I rebuilt mine years ago and have left well enough alone since. It's good to have a fresh perspective on this.

    BTW, I have got to think that someone must have won some kind of engineering razzie for this brake design. Either that or they were hoping to make their fortune selling special SECA master cylinder filler funnels.

    Cheers,
    Paul
     
    SQLGuy, Sep 25, 2009
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