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Hello All,
I recently acquired this 1980 CB400t Hawk, I believe everything is in fine working order other than the front brakes, where the lever is quite hard and are not very powerful, and after about 100kms have started to squeal.
Here's a picture, I will be removing the crash bars as they vibrate and interfere slightly with the cables. I haven't made up my mind about the luggage rack quite yet.
Anyway, I've ordered a new master cylinder because when I tried to bleed them the first time, there was not enough pressure being generated to get the fluid out of the bleed nipple. I've since realized this may not be the problem because I clamped the brake line immediately below the master cylinder and the lever became very hard. The brake lines look like they've been replaced as the bolts at either end are pristine.
I noticed when trying to reverse bleed (with syringe applying pressure from the bleed nipple so that the fluid is pushed out through the master cylinder), that brake fluid leaks from the bleed nipple (only when opened, no leaks when closed). Is it possible that the bolt is stripped and now doesn't seal properly?
After using paper towels to absorb the leaking from the bleed nipple, I managed to get some amounts of quite rusty brake fluid to come out the top. Now seems like the lever has become a bit softer, but the brakes go from weak at first to grabbing with a big squeak as they stop (compared to a metal on metal squeal before)
There's a very small space (just enough to see light) between the brake pads and rotor without brake, but you can see them grab and release upon brake application/release.
I'm thinking calipers are what I should take apart next to investigate condition of piston etc. but I'm not really sure how I can drain the system before doing this with the leaky bleed nipple and the lack of master cylinder pressure.
Hopefully some of my tests are useful and can be made sense of by someone
I recently acquired this 1980 CB400t Hawk, I believe everything is in fine working order other than the front brakes, where the lever is quite hard and are not very powerful, and after about 100kms have started to squeal.
Here's a picture, I will be removing the crash bars as they vibrate and interfere slightly with the cables. I haven't made up my mind about the luggage rack quite yet.

Anyway, I've ordered a new master cylinder because when I tried to bleed them the first time, there was not enough pressure being generated to get the fluid out of the bleed nipple. I've since realized this may not be the problem because I clamped the brake line immediately below the master cylinder and the lever became very hard. The brake lines look like they've been replaced as the bolts at either end are pristine.
I noticed when trying to reverse bleed (with syringe applying pressure from the bleed nipple so that the fluid is pushed out through the master cylinder), that brake fluid leaks from the bleed nipple (only when opened, no leaks when closed). Is it possible that the bolt is stripped and now doesn't seal properly?
After using paper towels to absorb the leaking from the bleed nipple, I managed to get some amounts of quite rusty brake fluid to come out the top. Now seems like the lever has become a bit softer, but the brakes go from weak at first to grabbing with a big squeak as they stop (compared to a metal on metal squeal before)
There's a very small space (just enough to see light) between the brake pads and rotor without brake, but you can see them grab and release upon brake application/release.
I'm thinking calipers are what I should take apart next to investigate condition of piston etc. but I'm not really sure how I can drain the system before doing this with the leaky bleed nipple and the lack of master cylinder pressure.
Hopefully some of my tests are useful and can be made sense of by someone
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