Author Topic: Front brake lever travel  (Read 1476 times)

Offline Lobo

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Front brake lever travel
« on: April 09, 2019, 11:06:28 AM »
Ok, so I need to take up weight lifting...
My K2’s front brake lever begins to bite at about 1/2” travel, with full brake at about 1” - ie my fingers are still pretty much at full stretch.
My mate’s K1; and indeed my 400F, have far gentler brake feels, and are far more efficient hand ergonomics wise.
Any tips to fettles this - barring topping up the system with air!
Ta,
Simon.

Offline Johnwebley

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Re: Front brake lever travel
« Reply #1 on: April 09, 2019, 11:52:14 AM »
Do you need lots of squeeze to get it to stop?
Maybe  softer pad.if you can get one.
Or.has the pad seal hardened and not retracting the pad enough.

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Offline Lobo

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Re: Front brake lever travel
« Reply #2 on: April 09, 2019, 12:11:21 PM »
Hi John, yep... needs lots of force indeed - there’s no way the front wheel would ever lock under normal conditions.  The pad is from DSS - if anyone can suggest a better supplier? (that said, my 400F pads are DSS too - this stops ok and with comfortable effort)
(The brake is in good mechanical working order... the bike was recently shipped to Oz, and for asbestos regs I took out the pads. What I’m saying here, is the Caliper was serviced / checked / lubed in the last 4 months. The bike has always been this way)
I guess, as a starter for ten I’ll back off the caliper adjusting bolt a couple of turns and see how that goes...
« Last Edit: April 09, 2019, 12:17:09 PM by Lobo »

Offline hairygit

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Re: Front brake lever travel
« Reply #3 on: April 09, 2019, 12:16:13 PM »
If it's always been like it, are you sure it hasn't had a larger bore m/cyl fitted (such as would be used for twin discs) at some point in it's life? That would give the symptoms you describe.
If it's got tits or wheels, it's hassle, if it's got both, RUN!!!

Offline Lobo

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Re: Front brake lever travel
« Reply #4 on: April 09, 2019, 12:20:14 PM »
Thanks hairy... can’t be sure of anything bearing in mind it’s 47yo(!) - but I did service the m/cal when I bought the bike - using a DSS kit. Everything fitted as advertised...

Offline steff750

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Re: Front brake lever travel
« Reply #5 on: April 09, 2019, 03:56:47 PM »
 ;) hi have you bled the system? or changed any brake pipes ,check that the rubber pipes don't swell when you pull the lever, if that is the case they will need replacing, although you live in OZ . you might well have moisture in the brake fluid
 it does sound like there is air in the system, you can try the old way and back bleed the system remove the master cylinder cap and using little short pulls of the lever you are checking for bubbles coming back up into the master cylinder BEWARE any long pulls will send a jet of brake fluid over you nice paint work so keep some rags handy
the best way is to replace all the brake fluid with a power bleeder and if they are as hard as a cb750 to bleed that may well be your only solution good luck with that
« Last Edit: April 09, 2019, 06:45:02 PM by steff750 »

Online Moorey

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Re: Front brake lever travel
« Reply #6 on: April 09, 2019, 07:40:55 PM »
What I have know happen in hydraulic hoses is a fault to develops in the inside of a hose and as you increase the pressure fluid is forced between the braiding in the hose and the lining. the lining then closes down effectively sealing off the hose so no more pressure can get through to where you want it, ie the calliper, but this very rarely happens. If you were to blow through the hose everything would seem fine also no bulging of the hose occurs as the braiding is intact.

Offline Lobo

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Re: Front brake lever travel
« Reply #7 on: April 09, 2019, 09:38:36 PM »
Thanks Steff... the stuff you describe would surely manifest as a spongy brake lever... mine is the opposite - after about 1” of travel is rock hard. Regardless, it was bled (tho’ not fresh fluid) a few months ago.)
Moorey - your explanation certainly best describes what I’m experiencing, and changing the hoses might be the best way to go. (though these were all new about 5 yrs ago when I restored the bike). I’ll have a good gander today & see if I can notec any bulgings under pressure. Thanks.
Simon

Offline flatfour

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Re: Front brake lever travel
« Reply #8 on: April 10, 2019, 08:32:05 AM »
The same happens with my CB750 K2. The front brake lever has a very short travel, whereas on my CB500 K1, the lever travel is around a third of the total available, with a much gentler "bite". I believe that the reason is that the CB750 has a DS replacement master cylinder on it, whereas the 500 has the original still fitted. The DS master cylinder has flutes in the reservoir, the original is a smooth finish.

Pads are the same in both bikes, DS replacements for the originals.

Offline Lobo

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Re: Front brake lever travel
« Reply #9 on: April 10, 2019, 08:49:52 AM »
... thanks flatfour, this could be the answer as the master cylinder does have a newish look about it. Moorey... I pumped the lines hard, and couldn’t detect any ballooning at all. Given the hoses are only 5yo / no bad weather / low mileage / adorned / moly coddled etc I can’t really believe they’re failing. Dang... and maybe an evening on eBay, though who knows what you’d be buying.

Online K2-K6

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Re: Front brake lever travel
« Reply #10 on: April 10, 2019, 09:23:06 AM »
I feel that there could be elements of many previous posts that will be affecting it.

The lever travel is linked to how soon the passage into the reservoir is closed off during lever stroke.  As Steff says,  if you squeezed the original quickly enough you'd get a little feedback visible with the cap open.  Once that locks off completely the line pressure then builds properly,  if this is a soft close it will give you more lever travel.

My recall of K2 and K6 was that the lever was quite soft and would probably go to about half travel if set up well.

But of the F1 it seemed more dead and harder to get lever travel.  Whether it changed spec between the two I've no idea.  But if it did and the pattern part is F1 based,  then it could account for some differences in feel and travel.
Or just that the pattern part doesn't quite replicate the internal geometry of an original.

An original master with refurbished seals may give you a different feel.

Online Moorey

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Re: Front brake lever travel
« Reply #11 on: April 10, 2019, 12:11:33 PM »
... thanks flatfour, this could be the answer as the master cylinder does have a newish look about it. Moorey... I pumped the lines hard, and couldn’t detect any ballooning at all. Given the hoses are only 5yo / no bad weather / low mileage / adorned / moly coddled etc I can’t really believe they’re failing. Dang... and maybe an evening on eBay, though who knows what you’d be buying.

I did say there would be no bulging of the hoses caused by this type of fault in a hose. Maybe I should have stated even under pressure.  :)
« Last Edit: April 10, 2019, 12:13:13 PM by Moorey »

Offline Rob62

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Re: Front brake lever travel
« Reply #12 on: April 10, 2019, 01:19:17 PM »
My recent experience of the DS pads is that they offer low levels of bite. I replaced my pads with EBC V pads (semi sintered) at about £25 a pair. Much better bite almost immediately after fitting.

Offline Woodside

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Re: Front brake lever travel
« Reply #13 on: April 10, 2019, 08:46:25 PM »
Have you a link Rob for them in the UK...I can find them in germany?

Offline Rob62

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Re: Front brake lever travel
« Reply #14 on: April 21, 2019, 09:21:00 AM »
Have you a link Rob for them in the UK...I can find them in germany?

Here you go, 2nd item on the page, 28 quid..
https://ebcbrakesdirect.com/motorcycle/honda/cb-750-k0-k5/1969-1975/36870#

 

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