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Discussion Starter #1
I have a 75 CB750k. The front break was stuck when i got it. I took it apart and it was very dirty. I flushed the fluid and lots of crud came out. Once I put it back together it worked 100% better but it still doesn't feel right. When i engage the brake it works but then sticks a little after it is disengaged.

How does the piston return to the off position? I did not take the piston out when I took it apart. I only cleaned the caliper and the small disk between the caliper and the piston.

Should I take the piston out or is it not meant to come apart?

Thanks, Again.

P.S. is it possible to post too many questions on this forum. My wife is giving me a hard time.
 

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Yes, you've got to take the piston out to properly rebuild the caliper. Just remove the caliper from the forks, take out the pads and set them aside and, keeping the master cylinder reservoir full, pump the brakes until the piston pops out. Inspect and clean out the inside of the caliper VERY GOOD (like, NO dirt, rust or any other crap in there).

Likewise, inspect and clean the piston itself. I've used 1000 grit sandpaper to remove oxidization, but be careful not to sand too hard on the aluminum piston! Check the rubber o-ring (and the groove it rests in). It should be good and soft. Its a good idea to replace this (check your local Honda dealer).

Once everything is super clean, push the piston back into the caliper (you can use a c-clamp to help you push evenly), making sure the o-ring and piston do not get damaged in the process. Bleed the system and you're done.

By the way, early Honda single piston calipers just kinda suck in my opinion but, feh, they work.

Honda go sideways!

http://groups.google.com/group/co-ohvinmoto
 

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Yes, you've got to take the piston out to properly rebuild the caliper. Just remove the caliper from the forks, take out the pads and set them aside and, keeping the master cylinder reservoir full, pump the brakes until the piston pops out. Inspect and clean out the inside of the caliper VERY GOOD (like, NO dirt, rust or any other crap in there).

Likewise, inspect and clean the piston itself. I've used 1000 grit sandpaper to remove oxidization, but be careful not to sand too hard on the aluminum piston! Check the rubber o-ring (and the groove it rests in). It should be good and soft. Its a good idea to replace this (check your local Honda dealer).

Once everything is super clean, push the piston back into the caliper (you can use a c-clamp to help you push evenly), making sure the o-ring and piston do not get damaged in the process. Bleed the system and you're done.

By the way, early Honda single piston calipers just kinda suck in my opinion but, feh, they work.

Honda go sideways!

http://groups.google.com/group/co-ohvinmoto
 

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what he said.

'72 cb750
'75 cb750
'76cb750
'82 cx500 (but mine is cool, i swear. Why don't you believe me?)


Edited by - pampadori on Jan 18 2008 08:26:01 AM
 

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what he said.

'72 cb750
'75 cb750
'76cb750
'82 cx500 (but mine is cool, i swear. Why don't you believe me?)


Edited by - pampadori on Jan 18 2008 08:26:01 AM
 

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Discussion Starter #6
Thanks for the help.

I called a couple places and was told that they don't have rebuilt kits for the 750k5 and that Honda doesn't make that specific pisotn o-ring.

I did find a caliper rebuild kit for the 77-79 750f's. Does anyone know if the 77f front break is the same as the K5?

Or, doesn anyone know of a source for the piston o-ring?

Thanks.
Mut
 

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Discussion Starter #7
Thanks for the help.

I called a couple places and was told that they don't have rebuilt kits for the 750k5 and that Honda doesn't make that specific pisotn o-ring.

I did find a caliper rebuild kit for the 77-79 750f's. Does anyone know if the 77f front break is the same as the K5?

Or, doesn anyone know of a source for the piston o-ring?

Thanks.
Mut
 

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I'm no Honda expert, but just in general clean up the master cylinder too. Crud in mc may be slightly hanging the piston or partially plugging the bleed back hole and causing it to hold a little pressure.
 

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I'm no Honda expert, but just in general clean up the master cylinder too. Crud in mc may be slightly hanging the piston or partially plugging the bleed back hole and causing it to hold a little pressure.
 

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You might want to check the FAQ section, I seem to recall that I might have addressed this there.

Ken

AHRMA 412
Vintage racing - old guys on old bikes
 
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