Modern Vespa

So, as noted elsewhere, managed to get air in my brake lines when flushing my BV. I've had good luck with the simple brake squeeze up until now, but I know BVs are notorious for being a PITA.... I've located a Mityvac which may be my best option, but I've heard comments about reverse flushing, and IIRC possibly using a syringe with fluid. (MadisonSully, are you here??).

Any thoughts on pitfalls of such or other alternatives? I know it's been discussed and opinions vary, but while I'm getting ready to go at things, it'll give me something to mull over.....

Edit: I did find the thread with the flushing details....but let's see...

Single circuit brakes are the Ginormous PITA ever, and never back flush any brake system. Clean fluid from the top, dirty fluid down and out.
Think like a snail or turtle, slow and steady, cavitation and air bubbles are your nemesis. If the bubbles develop, wait another day to allow them to dissipate.

Okay, another follow up. Does anyone know about the existence of a portioning valve on a 2017? Something in the back of my brain tells me they no longer have linked brakes, but I could be wrong. I could take off more plastic and find out, I suppose.... I found JKJ's post on his "moment" but that was on his 2013...

I don't know about the BV - but the GT and non-abs GTS brakes can only be reliably bled by back-filling. Let the air go the way it wants to!

Understood!, as long as the system is clean as a whistle IMHO.

Gleaned;
Braking fluids DOT 3, DOT 4, and DOT 5.1. are hygroscopic or absorb water and that is why brake fluids have two boiling point values. On the other hand, DOT 5 is a highly hydrophobic silicone formulation, or it repels water, making its boiling points more stable (260 °C dry boiling point and 180 °C wet boiling point)

easier for the bubbles to go up then down


I use a turkey baster to suck out old fluid from the master cylinder as it fills.
or you can use the mighty vac to suck it out

I also use an old style pressure pump to fill from the bottom its like a jar with a trigger style lever.

I live close to the equator

well you can always rotate the scooter upside down and do it that way I suppose.

If need be, I can put it on a spinner and let momentum do the work for me.

please post some pics

I would but don't want to violate rules I haven't yet read, being a new member an all.

with my GTS with ABS I find pushing from the caliper using a large syringe is effective.

I've used a syringe and filled from the caliper on a few different bikes. If theres air in the system it seems to work ok.

Seeing I have what I need, that's the plan! I'll keep you all posted!

Of course the weather's turned and I have an inhospitable garage now, but...fortitude!

^^^^ This. If replacing a brake hose, or there's air in there, reverse filling/bleeding is the answer. If it's just replacing time-expired brake fluid fill from the top is quite a bit easier - in fact I tend to just let gravity do the job. Put a tube on the nipple, open it up, and just keep dribbling fresh fluid in until the tube shows clear fluid again.

This is very timely and helpful as I am rebuilding the brakes on an old dirt bike. So I'm starting with new lines, an empty master cylinder, etc.. Start from the bottom and push everything up. Got it.

after attaching the lines to the caliper pre fill them before attaching to MC .

That could make it slightly easier - yes. If using a Mityvac (one that can push as well as pull) you'd probably not notice the difference though.

Not having luck with with the syringe push so far. I did try the gravity method on the front and can only surmise that I went too far as now the front brakes are soft too. FML.

Has anyone seen an estimate of fluid volume in the system? I'm on the BV, but curious about the GTS as well.

I had a question on the push about preventing air from the hose entering...bubbles sort themselves...thank you, gravity!

Get you one of these. By far easier to use than a mity vac.

my tip on that is use *a lot of force* on a big syringe. use enough hose that you can watch the inside of the master cylinder, you want to create a little fountain effect.

I'll always use a glass drink bottle with rubber hose and you cannot stop me. 100% gravity, I think some of my cylinders are firing correctly now.

I have only ever push bled from the bottom.
As long as you avoid any air bubbles in the syringe and tube, you are using pressure, so no air will get in the system.
But, once you have air in there, it's a pain to get out.
I'd still push bleed from the bottom though; everyone saying the air bubbles want to go up is quite correct.

Meaning? Pushing a LOT of fluid through?

I'm sure technique has as much to do with it as volume.


...Is it just me or does that sorta sound familiar...?

Maybe I need to suspend a disco ball over my workspace?

Sort of a pipe dream that I might have a bit of luck to report on. Did reverse flush maybe 50 cc of fluid on the front brakes, no change. Not surprised, but hope springs eternal.

So, doing a deeper MV dive.

A new item I ran across is someone saying that a dealer told them that the ABS system needs to be running to purge air there(?) thus requiring dealer computer input.. Has anyone heard that before? If so, hauling it 60 miles up the road is on my horizon.

Also, still wondering if I have linked brakes or not....I know on older models there was, and I believe it was JKJ that got results by digging into the front end and finding another bleed nipple. I've yet to go that deep into the body, so that could be an excellent misadventure..

MadisonSully referred opaquely to "technique." Is there anything more specific that I could be doing? More rapid flow of fluid? I think the only way I can manage that is having my lovely assistant with a syringe at the top end and perhaps use a clamp or physical grip on the caliper end so I don't blow the hose off.....

Had someone in my office singing the praises of the MiteyVac. It's a small investment, but as I was work-bound at the moment, I looked around online and found some inexpensive hose connectors for the bleed nipples to court disappointment from a new angle.

I'm giving myself until Monday to call the dealer.....Not much snow so far, with luck I can get a dry day and spend the day there to wait on it....

Thanks, all.

If no codes are shown and brakes work. Forget about it. Pass the Salt

Get a definitive answer on this before spending any more time or money

Good advice. Everything I've seen suggests no...the 2013 model had it, but looks like it disappeared with ABS braking. Maybe not definitive, but doubting that is my nemesis.

The 2013 didn't have ABS. That's probably the difference.
With my Primavera I didn't want to mess with the ABS, so I had Scooterville do it. I'll have them do my BV400 too when the time comes.