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Discussion Starter · #1 ·
In this forum because it's not my passat ( phew! ).

Helped a friend this weekend bleed the front hydraulic brake on his scooter. It's been 3 (!) years since he bought it and it was pretty dark and cruddy.

So, I volunteered my services and started a flush/bleed of the scooter. However, due to my not paying attention, the initial phase of pumping out the old fluid resulted in a bit of air sucked into the line.

I was a bit chagrined but not bothered initially, as I figured any air would be bled out; and since we were doing a full flush it wouldn't change the amount of fluid needed. So I filled the reservoir and continued.

After adding the new fluid the dynamic of the bleed changed. Instead of a good long squirt of fluid per pull of the handle, there was much less, and it seemed as though the cylinder wasn't completely re-filling with fluid when the handle was released.

I double-checked and we were using the proper (DOT-4) fluid from a new bottle.

At the end of the bleed it seems that after tightening the bleed screw, the brakes need 2-3 pulls to firm up, after which they stay nice and tight, no leakage.

I haven't yet test-driven the scooter following the bleed, but I imagine there must be a bit of air trapped in the line or the master cylinder. I'll find out after work tonight if the front brake works properly.

If not, my only thought is to do a reverse-pressure bleed and see if I can get any air bubbles out through the reservoir. Any other ideas? The results of my searches generally indicate "don't let the reservoir run dry" but without any prcedures should that happen (with the exception of, you'll have to start bleeding again.)

So, feel free to poke me with the idea/clue/doofus stick!
 

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Retired PassatWorld Staff
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Pump them up B4 opening the bleed screw, and stand back. This will compress the air and move it further down the system... out of the piston area. Then fill the reservior again.

Repeat until you don't have a soft lever, and then bleed as normal to remove the last of the air.
 

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Discussion Starter · #3 ·
Pump them up B4 opening the bleed screw, and stand back. This will compress the air and move it further down the system... out of the piston area. Then fill the reservior again.

Repeat until you don't have a soft lever, and then bleed as normal to remove the last of the air.
Well, that's actually what the remainder of my bleed devolved into. 2-3 pumps to build up pressure, bleed, close bleed screw before brake lever meets handlebar. Each time the bleed screw was opened ( I was using tubing and a check valve ) the lever would get soft, then firm up after a couple of pumps.

I went for a test drive last night... it's pretty tight. There is absolutely no sponginess in the lever once it's sealed. In fact, there's not quite enough free play, it's now a scooter with 1-finger braking :) I guess i'll just do another flush in the spring before he hits the road, just to be sure.
 
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