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Author Topic: Caliper piston size?  (Read 1398 times)

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Offline yeyoPR

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Caliper piston size?
« on: September 03, 2015, 04:12:50 PM »
Hello all,
So I'm rebuilding the caliper on my 1976 CB550K and somehow lost the original piston, and the piston I received from 4into1 is too big for my caliper.  What size should I look for?
My caliper is the kind that has like a small lid over the piston and doesnt have a groove for the seal, like this one:

https://acaferacerisborn.files.wordpress.com/2012/07/0021.jpg

Sorry if it has been answered before, I couldnt find it.
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Offline mrfish2

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Re: Caliper piston size?
« Reply #1 on: September 03, 2015, 05:35:54 PM »
Which piston did you order from 4into1? If it was listed as a CB550 piston then it should fit, otherwise you might not have the stock brake caliper on your bike. Pics of your caliper would help.
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1976 CB550K            1979 XS1100
1980 CB650C - Sold

Quote from: crazypj on October 19, 2008, 09:14:45 PM
It's a little motor and likes having the tits revved off it.

Offline scottly

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Re: Caliper piston size?
« Reply #2 on: September 03, 2015, 05:47:00 PM »
The 550 caliper has a 38mm piston. In the pic you linked, the top "lid" has been removed, although it's not meant to be removed. You may have gotten a K7/8 750 42.8mm piston?
K7 on the left, 550 on the right:
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Don't fix it if it ain't broke!
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Offline yeyoPR

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Re: Caliper piston size?
« Reply #3 on: September 03, 2015, 05:57:31 PM »
This is my caliper.
The piston I bought was listed in 4into1 as a CB550 piston.
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Offline mrfish2

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Re: Caliper piston size?
« Reply #4 on: September 03, 2015, 06:00:36 PM »
You do realize that the piston in your pic isn't out of the caliper, right?
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1976 CB550K            1979 XS1100
1980 CB650C - Sold

Quote from: crazypj on October 19, 2008, 09:14:45 PM
It's a little motor and likes having the tits revved off it.

Offline yeyoPR

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Re: Caliper piston size?
« Reply #5 on: September 03, 2015, 06:06:26 PM »
That would explain why I cant find it!  :o :o  :-[ :-[ ;D
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Offline scottly

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Re: Caliper piston size?
« Reply #6 on: September 03, 2015, 06:06:49 PM »
I can see the stake marks in that piston that locked the original lid. The early 750 38mm piston had a domed lid that dropped into the open top of the piston.
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Don't fix it if it ain't broke!
Helmets save brains. Always wear one and ride like everyone is trying to kill you....

Offline scottly

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Re: Caliper piston size?
« Reply #7 on: September 03, 2015, 06:07:46 PM »
How about a pic of the new piston? ;)
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Don't fix it if it ain't broke!
Helmets save brains. Always wear one and ride like everyone is trying to kill you....

Offline yeyoPR

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Re: Caliper piston size?
« Reply #8 on: September 03, 2015, 06:16:54 PM »
This is the new piston
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Offline scottly

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Re: Caliper piston size?
« Reply #9 on: September 03, 2015, 06:20:16 PM »
Pump the old piston out of the caliper, clean it up and replace the seal, and install your new piston. ;)
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Don't fix it if it ain't broke!
Helmets save brains. Always wear one and ride like everyone is trying to kill you....

Offline yeyoPR

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Re: Caliper piston size?
« Reply #10 on: September 03, 2015, 06:25:56 PM »
hahah I will! thanks everyone! case closed, excuse my newbieness  :P
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Offline DaveBarbier

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Re: Caliper piston size?
« Reply #11 on: September 03, 2015, 06:31:15 PM »

Quote from: mrfish2 on September 03, 2015, 06:00:36 PM
You do realize that the piston in your pic isn't out of the caliper, right?

Haha!
"I lost my piston."
"You haven't taken your piston out yet."

Reminds me of a Simpson's episode.

Homer: "Uhh, I lost my map."
Smithers: "You haven't been issued a map yet."
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Offline yeyoPR

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Re: Caliper piston size?
« Reply #12 on: September 03, 2015, 06:52:56 PM »
hahah!  yes  :-[  very Homer like...but I have worse stories  :P
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