GT550k hissing sound when squeezing brake lever

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SClubSuzuki
On the street
Posts: 22
Joined: Mon Jan 26, 2015 2:04 pm
Country: USA
Suzuki 2-Strokes: Suzuki A50, S32 Olympian

GT550k hissing sound when squeezing brake lever

Post by SClubSuzuki »

Hello folks, I rebuilt my brake system from top to bottom, including the master cylinder with a new piston kit. I’m having real trouble getting it to operate properly, after much bleeding the lever still goes all the way down without effect. I suspect the master cylinder bore may be shot because if I squeeze the brake lever quickly I hear a distinct hissing sound, like air is escaping. No fluid is leaking however, it’s tight as a drum. At first I thought it was the rubber dust boot that protects the piston, but I removed it and the hissing is still there. Unless I somehow installed the piston seal incorrectly? Any advice? Thanks in advance..
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Alan H
Moto GP
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Suzuki 2-Strokes: 4 x GT550s - J, M, A, B.
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Re: GT550k hissing sound when squeezing brake lever

Post by Alan H »

Worst case scenario, just get a new master cylinder off ebay.
There are quite a few available that look similar, and will do the job ok for not many $$.
If you really must use the original, make sure that all the holes in the base of the m/c are perfectly clean and the castings are shiny and dirt free inside.
Think of how stupid the average person is, then realise that half of them are more stupid than that.
SClubSuzuki
On the street
Posts: 22
Joined: Mon Jan 26, 2015 2:04 pm
Country: USA
Suzuki 2-Strokes: Suzuki A50, S32 Olympian

Re: GT550k hissing sound when squeezing brake lever

Post by SClubSuzuki »

Thanks Alan, I will disassemble it and double check. If all looks good I’ll go to eBay
SClubSuzuki
On the street
Posts: 22
Joined: Mon Jan 26, 2015 2:04 pm
Country: USA
Suzuki 2-Strokes: Suzuki A50, S32 Olympian

Re: GT550k hissing sound when squeezing brake lever

Post by SClubSuzuki »

Haven’t torn into it yet but just realized that I used DOT 4 fluid instead of 3, wondering if there’s a viscosity difference that would cause my problem?
karl pa
Yeah Man, the Interstate
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Suzuki 2-Strokes: GT
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Re: GT550k hissing sound when squeezing brake lever

Post by karl pa »

DOT 4 shouldn't cause any difference from DOT 3, Sometimes the brake system just acts like that, if assembled correctly, try bleeding at the banjo bolt and get the master cylinder bled. then work down the lines.
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