Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: Mikep328 on August 14, 2023, 09:37:56 AM
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I have maybe 12-15mm of play in the brake lever before it contacts the master cylinder piston. As I have mentioned in my post re the brakes, they are quite good now - no issues at all with their function/performance. But that lever play does not seem correct.
I have read a post where an individual filed down the brake lever where it bears against the piston so as to be able to apply more hand pressure and I'm wondering if that was done one this bike which might have some affect on play. If it was filed nicely, I'm not sure if I'll be able to tell by removing/looking at the lever. ::)
ALSO...I see in the parts diagram for the 400, item 365 that looks like some sort of rod or tube that fits in the master cylinder lever assembly. It looks like it might bear upon the lever in some way. Is that related to any lever play?
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Yes, that's the anti rattle bush.
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AHA! I'm pretty sure that item is not present based on a casual inspection of the master cylinder when I was doing the brake work. but I'll check to be sure.
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How much play do you have in the lever pivot? Any wear in the pivot bolt or lever will make the situation worse.
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Mine (part 365) had reverted to a pile of rust so I made another from some 6mm steel rod.
Very simple to make.
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Both my 400 & 500 had what I considered to be excessive movement in the brake lever - there was excessive travel before the lever part started to push down on the piston.
The internals on my 400 were beyond just fitting new seals so replacement was essential.
The DS master cylinder is I believe a different diameter piston - problem resolved as it has hardly any free play before the lever arm end touches the m/c piston.
I used the DS master cylinder on my 500 with the same good outcome.
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Mine (part 365) had reverted to a pile of rust so I made another from some 6mm steel rod.
Very simple to make.
Part 365 is rubber, not steel rod ::)
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As Graham says:
[attach=1]
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Just use a piece of rubber pipe as per Gareths photo, it was never metal.
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"How much play do you have in the lever pivot?"
There didn't seem to be any noticeable play in the pivot itself when I was working on the brakes but I'll check that closely tomorrow when I go to the garage (3/4 mile from the house). I was looking at new levers on DSS in case I needed one and see there is a pattern lever and an OEM lever for, of course, considerably more money. But in looking at the close up pic, the OEM seems to be a better quality item - with a bushing of (I assume) harder metal in the pivot hole rather than just a hole in the Al lever
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The pivot bolt gets worn and also the bush in the lever ;)
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If you look at the tip of the lever where it pushes down onto the end of the master cylinder what is the gap difference before you start to pull on the brake lever? However good the rest of the lever pivot is that play has to be taken up before the brakes start to work.
If that gap is say 2-3 mm by the time you multiply by the length of the actual leverage taking into account the length of the lever at the action end - call that around 70 mm you end up with some 14-21 mm of movement even with no pivot wear.
If my rough mathematics is wrong I am open to a better estimate.
I suspect back in the day as long as the brakes worked once the play is taken up with plenty of available travel before the lever meets the bars that was fine.
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I have no issue at all with the point at which the brake lever actually starts applying force to the piston and braking begins. Maybe I'm just being unnecessarily anal worrying about play in the lever but it just doesn't look right to see the lever not fully against the stop when the brake is "off." Does that anti-rattle bushing force the lever to stay in the fully open position when not being used?
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The pivot bolt and the bush, when in non worn condition, just stop the lever chattering. By what I can remember of Hettie, my 400/4 she had a couple of mm gap where you're talking about. You may have an aftermarket or wrong model lever fitted.
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Re bush material, as always I live and learn.
Anyway after overhauling my front brake I can make the tyre squeal which I couldn't before.