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  1. #1
    CB750 New Member Anthonyt's Avatar
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    Exclamation Weak front break

    Hey guys, I am new to the forum, just bought a 1979 cb750, and the front break is really weak looking to fix it but don't know how. I know literally nothing about bikes just to let yall know. where do i start? what do I tackle first? What am I looking for?
    thanks guys.

  2. #2
    CB750 Guru amc49's Avatar
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    SOHC or DOHC? Some get the years wrong. One disc or two? "Really weak' quite frankly says nothing other than it doesn't work, detail that better. Does lever get tight when you squeeze it or seem to give way? Did you check for brake fluid in it? Exact model and year is on a plate up on the steering head.

  3. #3
    CB750 New Member Anthonyt's Avatar
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    She is A cb750k LTD 10th anniversary, single disk, I think the pressure is really weak, the break is spongy and has no grip what so ever it just gives way, how do I increase the pressure in the tube?

  4. #4
    CB750 Addict madmtnmotors's Avatar
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    Quote Originally Posted by Anthonyt View Post
    the break is spongy and has no grip what so ever it just gives way
    Sounds like the master cylinder could stand to be rebuilt. You can get new packing straight from Honda for a reasonable price:

    http://www.hondapartsnation.com/oemp...r-cylinder-set

    Might as well replace the dust seal and piston seal in the caliper while you're at it:

    http://www.hondapartsnation.com/oemp...9-425-003/boot
    http://www.hondapartsnation.com/oemp...04/seal-piston

    There's a chance that you still have original, thirty-seven year old seals in your brake system. Disassembly, thorough cleaning, and repacking with new seals can make a world of difference. While you're at it, jettison that thirty-seven year old dry rotted rubber brake line for either a braided stainless line, or at least a new rubber one. Might as well top it off with a new set of pads too.
    I know, I know, "everybody else is doing that way"...

    High price to pay for being "stylish"...

  5. #5
    CB750 Guru amc49's Avatar
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    Like said, the master cylinder, humidity has gotten inside it. Probably will need to hone the body, and if corrosion damage is too deep then no seals on the planet will fix it. Commonly though you can get one hone/rebuild before the housing needs to be chucked. I have even reused the old seals if I can fold them all around to find zero cracks or corrosion dents and the rubber is still live. Reinstalled like that and hone only for no parts cost and the brake works for years. But then, I've done that type work so many times I can't count.

    I'd go through caliper too like said, whatever happened to M/C has happened to caliper too, it just hasn't failed yet.

  6. #6
    CB750 New Member Anthonyt's Avatar
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    thanks madmtnmotors new break lines are shipping, I also replaced the fluid and there was some air in the lines. so the breaks are working till the new parts come!

  7. #7
    CB750 Guru amc49's Avatar
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    They may work but with time the aluminum bore in the m/c gradually churns more and more corrosion bits into the system, once a bit of that stuff gets under a seal edge you lose it and instantly when it was working fine before. Why it's best to get in there to clean that all out and a quickie hone inside m/c and good and clean and you just bought yourself another 10 years of solid use with zero worries. The calipers generally not nearly so susceptible to that as the seals are quite a bit thicker.

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