Author Topic: New (to me!) '77 CB400F - US model  (Read 38178 times)

Offline mattsz

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Re: New (to me!) '77 CB400F - US model
« Reply #45 on: October 26, 2018, 06:53:48 PM »
Yes,  as you think,  it doesn't affect the wear as that is only the hydraulic force clamping it. And also same forces as the modern ""sliding " single piston type.

It is a bit cock-eyed though (in purist engineering principles) as they've started with a swing geometry so the pads will ultimately wear in a taper, then felt the need to give some sort of assistance plus limit to the assembly. Compared to the straight up design within the engine it does appear to be an odd compromise.

Ahh... the pads wear in a taper, too... never thought of that!  Love learning new things...

Offline mattsz

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Re: New (to me!) '77 CB400F - US model
« Reply #46 on: October 26, 2018, 06:56:17 PM »
Thanks, I'll look for some.  Does anyone know if the two "cross-head" screw driver shanks in the OEM tool kit are JIS-friendly?

I'd imagine they are BUT they aren't exactly case hardened so will break eventually, plus the handle is just not up to the job. The ones in the link are magnetic tipped as well, which helps a great deal in getting screws back into confined areas, especially carbs and such.

Yes, the handle leaves much to be desired - in its defense, it is portable!  I just thought I might use them until I get my own better tools...  Too late for the cable set screws...  :(

Offline Bryanj

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Re: New (to me!) '77 CB400F - US model
« Reply #47 on: October 26, 2018, 10:38:11 PM »
The other reason for the adjuster is that if everything is free vibration between pad and disc can push the piston back through the seal meaning extra lever travel to get the brake to work

Offline mattsz

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Re: Matt's '77 CB400F - US model
« Reply #48 on: October 26, 2018, 10:58:00 PM »
I was going to start a new thread, but for now I think I'll carry on with this one, since I'm still only dipping my toes in here...

Brakes:  I removed the caliper, and pumped the piston out before disconnecting the lines.  It was all very unexciting, I think I introduced some air into the system which made the piston only move about 0.5mm per lever pump.  There's some evidence of corrosion, but nothing like as bad as some photos I've seen.  The old fluid was a bit dark but fairly clean, and smelled very strong.  I'll rebuild the master cylinder and caliper this winter.

Here's some photos - I'm posting them as thumbnails that can be clicked on for a bigger view...

Not a very well-lit pic of the caliper's interior, but there's plenty of corrosion where the brake pad rests (at bottom of pic, hard to see), and a wee bit where the piston rides, just inside the rubber seal:

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A couple of the piston, showing some corrosion spots and one proper gouge:

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The back of the pad, obvious corrosion on the edge to match that inside the caliper:

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The master cylinder - not too bad.  I see two holes only, neither is a pin-sized hole that a guitar e-string might be used to clear:

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Offline mattsz

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Re: New (to me!) '77 CB400F - US model
« Reply #49 on: October 26, 2018, 11:03:33 PM »
I also couldn't budge either the bleed nipple nor the brake line fitting from the caliper - I just left them for now, will try to carefully coax them out later...

Offline K2-K6

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Re: New (to me!) '77 CB400F - US model
« Reply #50 on: October 26, 2018, 11:20:30 PM »
You have to be reallllly careful with those as they will snap off.  Think the common advice on here is to heat them first, but they can be very tricky.

Looks like it was mainly stuck on pad corrosion.  Rain and salted roads make easy work to get that going,  if you're not using in winter then obviously less likely.

Interestingly,  the original manual for the 750 says about the caliper,  to use "silicon sealing grease" all around those pads and the interface with the piston. Presumably they are trying to exclude water as that stuff really resists any ingress. It specifically states "Do not use molybdenum grease,  known as brake grease".

Offline mattsz

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Re: New (to me!) '77 CB400F - US model
« Reply #51 on: October 27, 2018, 12:30:27 AM »
You have to be reallllly careful with those as they will snap off.  Think the common advice on here is to heat them first, but they can be very tricky.

Looks like it was mainly stuck on pad corrosion.  Rain and salted roads make easy work to get that going,  if you're not using in winter then obviously less likely.

Interestingly,  the original manual for the 750 says about the caliper,  to use "silicon sealing grease" all around those pads and the interface with the piston. Presumably they are trying to exclude water as that stuff really resists any ingress. It specifically states "Do not use molybdenum grease,  known as brake grease".

I will be reallllly careful, I promise!

My download copy of the CB350F-400F service manual, which can be found just about everywhere, says "apply a coat of silicone sealing grease to the sliding surface of the calipers when installing the pads."  Doesn't say anything about the pad/piston interface though.  Is this grease heat resistant as well as water resistant?

Offline mattsz

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Re: New (to me!) '77 CB400F - US model
« Reply #52 on: October 27, 2018, 03:15:18 AM »
Yeah it's silicon, they use that stuff to make oven mitts out of these days.

 :-[ I suppose if I had thought about it, I would have made the connection...

Offline Bryanj

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Re: New (to me!) '77 CB400F - US model
« Reply #53 on: October 27, 2018, 08:17:09 AM »
You will find the hole in the master nearest to the pipe end reduces to the tiny one at the base of the cone you can see. Personaly i would replace that piston, they are not expensive and you only got one neck

Offline mattsz

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Re: New (to me!) '77 CB400F - US model
« Reply #54 on: October 27, 2018, 10:39:13 AM »
Personaly i would replace that piston, they are not expensive and you only got one neck

I will replace it - only one neck, as you say!  Are there new pistons/pads made from materials that won't corrode as much, or at all?

Offline hairygit

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Re: New (to me!) '77 CB400F - US model
« Reply #55 on: October 27, 2018, 11:09:19 AM »
Someone your side of the pond used to make them from phenolic resin, but I can't remember who, someone will.

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Offline taysidedragon

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Re: New (to me!) '77 CB400F - US model
« Reply #56 on: October 27, 2018, 11:16:00 AM »
Personaly i would replace that piston, they are not expensive and you only got one neck

I will replace it - only one neck, as you say!  Are there new pistons/pads made from materials that won't corrode as much, or at all?
There are stainless steel pistons available, the pads are not so much of a problem.
Gareth

1977 CB400F
1965 T100SS

Offline mattsz

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Re: New (to me!) '77 CB400F - US model
« Reply #57 on: October 27, 2018, 11:38:00 AM »
Just did a quick "phenolic" search - the name Kevin Hunter appears a couple of times.  Anyone with experience on this OEM/phenolic/stainless question care to chime in?

EDIT: Kevin Hunter hasn't posted on that forum in many years...
« Last Edit: October 27, 2018, 11:49:21 AM by mattsz »

Offline Bryanj

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Re: New (to me!) '77 CB400F - US model
« Reply #58 on: October 27, 2018, 12:50:40 PM »
Look up roger7500_1 on ebay. He is in UK but gives you some idea

Offline Seabeowner

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Re: New (to me!) '77 CB400F - US model
« Reply #59 on: October 27, 2018, 01:29:21 PM »
Just did a quick "phenolic" search - the name Kevin Hunter appears a couple of times.  Anyone with experience on this OEM/phenolic/stainless question care to chime in?

EDIT: Kevin Hunter hasn't posted on that forum in many years...
Godffeys's garage in the States. I always used stainless as they are cheaper, but they are heavier.
Phil
1971  CB500K0  Candy Jade Green or Candy Gold
1973  CB500K1  Candy Ruby Red
1975  CB550F1   Shiny Orange
1978  CB550K     Excel Black

 

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