Author Topic: CB400f front brake leaking  (Read 188 times)

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Offline jchilper

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CB400f front brake leaking
« on: February 09, 2019, 02:43:02 pm »
I had to rebuild the front brake. I rebuilt the master cylinder which was successful, no leaks and works as it should. Tore down the caliper, stripped the paint and sent it off to a powdercoater. Replaced the caliper seal, new lower pipe and added a speed bleeder (had it lying around from Shaun at Slingshot - RIP), put everything back together and lo and behold it's leaking where the pipe goes into the caliper body. It's as tight as it could be and it leaks. Didn't do this prior to the tear-down. I did all this because the piston was frozen. Why would this leak when I've used all OEM parts?? Only aftermarket on this set-up is the speed bleeder and replacement stainless lines (once again thanks to Slingshot). Anyone have an idea why it would be leaking brake fluid?
John H. #331
74 CB550
75 CB400F
76 CB750K6

Online BenelliSEI

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Re: CB400f front brake leaking
« Reply #1 on: February 09, 2019, 09:09:45 pm »
I had the same problem on my 1970 cb750K1 last summer. The short metal brake line (new) had a poorly made flair. It didn’t seat properly in the caliper, twisted off to one side. No amount of tight made it sit square. Have a look, I had to replace it with another one.

Offline jchilper

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Re: CB400f front brake leaking
« Reply #2 on: February 10, 2019, 11:35:16 am »
Pulled the little brake pipe and it sure appears to have some distortion at the flair. This was an aftermarket. Ordered a new NOS one from a guy on eBay. Crossed fingers.
John H. #331
74 CB550
75 CB400F
76 CB750K6

Offline robvangulik

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Re: CB400f front brake leaking
« Reply #3 on: February 10, 2019, 02:08:59 pm »
That pipe is made of rather soft metal, and it is possible to remodel the flared part so it fits hermetically onto the seat in the hole in the caliper.

Offline jchilper

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Re: CB400f front brake leaking
« Reply #4 on: February 15, 2019, 03:34:09 pm »
Since I don't have the flailing tool for that tiny diameter I went with an OEM. Firs perfectly. No more leak. (yay)
John H. #331
74 CB550
75 CB400F
76 CB750K6

 

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