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Caliper Piston Operation

Daniel

2014
CB650F ABS
Messages
347
Likes
231
Thread starter #1
Evening all, currently got no forks and decided to clean up the front calipers while they were free. I removed the speed sensor, pads, pad pins, retaining springs and brackets. I left the lines attached.

Cleaned them both with soapy water and toothbrush and then focused more on the pistons, pulling the brake lever to expose more of the piston and only 1 moved at a time. I carried on depressing the brake lever and eventually the other moved instead, neither moved simultaneously, only independently about 3mm at a time. If I put my thumb against one it would not move though, only the adjacent one.

Which brings me to my query, is this correct? Should only 1 move at a time? It was the same with the other caliper. To me it seems wrong but they move very smoothly, are very clean, not used hard and have little over 10,000 miles of use.
 
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Daniel

2014
CB650F ABS
Messages
347
Likes
231
Thread starter #3
Mine does that too. As did the front twin pot caliper on my cb500 (1997).

You didn't say which piston moved first?

J
Thanks that's reassuring then, felt like something was a-miss. Can't remember which moved first, may have been the lower one? As seen when mounted.
 

Daniel

2014
CB650F ABS
Messages
347
Likes
231
Thread starter #6
Yeh, only with a little brake fluid as per service manual.

Separate question, this red substance in the image, it's on fork pinch bolts and caliper mounting bolts but no mention of applying anything in the service manual. Anyone know what it is?
 

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