Brake master has very soft 1st pull after sitting overnight

[treckin]

As in the title, my 1st pull of the day on the brake lever is very soft. I am a car mechanic, so my understanding of automotive brake masters tells me the seals are going bad in the master, although I am definitely open to alternative theories. Has anyone else experienced this?

 

[psych0hans]

Yeah, the first pull is generally pretty soft for me as well, maybe try bleeding it first?

 

[treckin]

That's my thinking. I have a vac bleeder so, I give it a whack before I take it to the dealer for the master.

 

[aj@x]

Pull the lever in and throw a couple of rubber bands round it and the grip to hold it in, leave it overnight and see how you go.

 

[psych0hans]

Pull the lever in and throw a couple of rubber bands round it and the grip to hold it in, leave it overnight and see how you go.

It helps, but then it goes back to mush again pretty soon, so, do I need to open the reservoir cover and let the air out after I do this?

 

[gbabyracing]

No bleed it at the caliper. Bet you'll find an air bubble.

 

[ShinySideUp]

That's my thinking. I have a vac bleeder so, I give it a whack before I take it to the dealer for the master.

vacuum bleeders are better for moving fluid for flushes than actual bleeding. Just my two cents.

 

[Formula390]

Yeah, pick yourself up a vacuum bleeder / mighty-vac, or find a local buddy who has one, and bleed the brake system. The brakes on the Formula390 test mule went to crap after I managed to trigger the ABS the first time. I bled them with the mighty-vac real well, and with holding pressure on the pumped up system also EVER so slightly cracked the banjo bolt at the reservoir to bleed any air trapped there as well... you are going to crack it open JUST until you see the tiniest amount of fluid escape a TINY bit, then tighten it again... you're only going to crack it open every so slightly... keep a shop rag under the spot so you don't leak any fluid onto the bike itself. Then, do the lever pulled in overnight trick. I use zip-ties myself, as opposed to rubber bands. Generally it's a two man job... one person keeps the system under vacuum while the others job is to keep the reservoir filled. You'll pull fluid out FAST with the vacuum bleeder, so they have to be prepared to add. if you end up draining the reservoir and suck in air, you'll be worse off than you started... so pick a competent helper! Not one of your jackass friends that screws up everything. Or maybe that's just me who's best friends have a lack of good judgement... Hmmmm. I probably shouldn't shine a light on THAT particular character trait too strongly tho!