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Old 05-14-2011, 10:05 PM   #1
fizzer6hundred
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Default Need some advise on front brake bleeding

Hi I have a 1994 Yamaha FZR600 and I recently went down (I am ok thanks) on the right side. I am doing repairs and looking for advice on a not so simple hydraulic problem with the brakes.

Just finished with new brakes up front. Cleaned and inspected the calipers and they "look" fine.

I used a vacuum hand pump to bleed the system (bleeder on each caliper not on the master cylinder). Left caliper bleeds fine. right caliper bubbles all day long and I get "functional braking" but a mush brake lever.

Went the bike went down it hit the front brake lever. So I ma wondering this:

How do I tell of the leak is coming from the master cylinder or the caliper?
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Old 05-14-2011, 11:34 PM   #2
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Oh and by the way I have never seen any leaking fluid anywhere master cylinder calipers lines etc. And the level was not low.
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Old 05-15-2011, 05:13 AM   #3
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If you don't see a leak and level isnt droping, why would you think you have one?
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Old 05-15-2011, 08:40 AM   #4
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If you don't see a leak and level isnt droping, why would you think you have one?
Because of the air coming through when bleeding one side.....and the soft feel.

All I can suggest is changing to a "conventional" bleeding technique and paying particular attention to bleeding at the upper banjo bolt, which is where trapped air often hides.

THEN......when you think you've got it whipped, apply the brakes firmly and strap the lever in the operated position overnight. If it is still firm the next morning, you can be pretty much assured that there is no leak and things are in good shape.
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Old 05-15-2011, 10:45 AM   #5
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Thanks Easy rider, also I am using Valvoline Synthetic dot3/4 I assume that synthetic is ok to use on bikes?????

How do I purge air out of a banjo bolt?
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Old 05-15-2011, 03:28 PM   #6
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Thanks Easy rider, also I am using Valvoline Synthetic dot3/4 I assume that synthetic is ok to use on bikes?????
Yes IF the original fluid was DOT 4.

+1 on the bleeding proceedure. Might need to do it more than once.
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Old 05-15-2011, 05:49 PM   #7
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DOT4 is safe to mix with/supercede DOT 3. It is all I use in any vehicle, has been for most of a decade.
AFAIK, nothing comes with DOT 3 anymore and hasn't for a LONG time.....like the '50s maybe.

DOT 4 is not mixable with everything though. With DOT 5 synthetic for instance, it makes something like paste.

Best to read and follow the directions !!
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Old 05-15-2011, 06:44 PM   #8
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If you look at the bottle of most DOT4 brands they say DOT4 and DOT3 (backwards compatible).

I just tried bleeding the system again after a test ride yesterday with weak hydraulics (I know not the smartest move but I was taking it easy). after 24 hours and another bleed it does feel better but still not rock hard. The brake almost makes it to the throttle.

Thinking about trying to bleed the Banjo bolts is not something I think is very doable for me.

So I am wondering what magical bleed systems do the pro shops use. And why is better than my MityVac and regular pump method?

Last edited by fizzer6hundred : 05-15-2011 at 07:03 PM.
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Old 05-15-2011, 09:34 PM   #9
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A vacuum bleeder (like Mity Vac) admits air into the system past the threads on the bleeder valve. They're great for pumping high volume when you want to replace the fluid, but for getting the last few molecules of air out, you really have to do it the old fashioned way.
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Old 05-16-2011, 08:15 AM   #10
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Thinking about trying to bleed the Banjo bolts is not something I think is very doable for me.

So I am wondering what magical bleed systems do the pro shops use. And why is better than my MityVac and regular pump method?
Just why is it "not doable" for you ??
You can crack the bolt loose before you squeeze the lever to pressurize the line. That makes it a little less messy and easier to deal with.

The shops bleed at the calipers......and at both sets of banjo bolts if necessary.

If you have a good relationship with a shop, they might do it for you for next to nothing; certainly not more than $50.
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