Modern Vespa

I've been struggling to get the rear brakes at 100% almost since day 1 after I bought this 2007 GT200 in August. They start off squishy, then would bottom out completely, then come back, then go out...

I tried bleeding them. I kept seeing air as I drew out the fluid. But the brakes at least continued to mostly work, just always squishy and sometimes bottom out/lose power briefly

2 weeks ago they complete crapped out on my way home. They were completely dead. Not even a little grip. Driving home was a little nerve-wracking.

I couldn't even get them to bleed. I would squeeze the brake and nothing happened at all.

I replaced the master cylinder and did a visual/touch inspection of the brake line. I was able to bleed after the replacement. There was a lot of air in the line (yes, I let the reservoir go empty at one point and had to start over) and I bled the s**t out of them. I told a friend I now have 'the cleanest brake fluid in all of Tennessee". They got firmer and it seemed good but...

I noticed when I closed the bleed valve and released the brake, air would start bubbling up from the valve into the drain hose. And they have gotten better - they function, but I'm still having the fading in and out of effectiveness.

I'm stumped. I did notice a while ago that the bleeder valve doesn't seem to fit properly - it sticks up a lot (can see about 1/4 inch of threads) and it has a very slight 'wiggle'. The front valve, in contrast, screws all the way down and is firm, no wiggle. Is it possible to replace the valve? I couldn't find one on ScooterWest, so maybe they only come when you buy a full brake caliper?

Help! I bought this second hand as my only motorized transport, so I'm desperate to get this functional before fall rain starts (no garage).

Side note - there are so many missing screws and broken plastic bits on this scooter, I would not be shocked to find out someone, for some reason, replaced the valve with something incorrect.

I have always reverse bled the brakes because the conventional way never seemed to work for me. I use a 50 ml syringe with a short length of rubber onto the rear bleeder. Check the master cylinder while doing it so it doesn.t over flow because it certainly dissolves the plastic.

Are those the original brake lines? Might be time to throw on some stainless ones? I don't think it'll solve your problem, but you're in there doing all that work anyway. Might be the time to do it.

You can replace the bleeder valve. Some have a small o-ring near the tip that you cant see unless totally removed. However, if the caliper body is somewhat stripped out where the valve is inserted from over zealous wrencher, you may need a whole new caliper body. Take a look at Scooterpartsco or PM Motovista. He is a member in here and you could probably help you out.

If you have a piece of hose on the bleed valve, with brake fluid in it, you can usually keep it from sucking air back in.
One trick I've resorted to, after seeing other people do it, is to remove the rear caliper from the bike, hang it up as high as it will reach, with the bleed nipple pointing up, then bleed them that way. Sometimes you can get a little air pocket in the caliper, and moving it around will get the bubble to migrate up towards the valve.

GT already comes with stainless lines

also, that's a massive amount of work.

this is my guess as well.

a bad bleeder or stripped caliper. my money is on the caliper from the description. a few photos would help tremendously.

I knew I could learn something from you today.

thanks for the backhanded compliment. I wish I could say the same.

Where was the backhand? All compliment.

PS: I'm not a mechanic, I doubt very much I could ever teach you anything on the technical side of Vespe, nor do I pretend like I could.

And do I need to squeeze the brake lever while I am feeding new fluid or the brake can remain "off"?

Ask and ye shall receive…are these what you needed?

Interesting.
Man, I was really hoping it would not involve removing the tire at all. I really, really was. I need to learn how to do it though.

I am thinking the threads may be stripped though. Sigh. The scooter rides beautifully, IMO, but the brakes have been hard to resolve…and expensive out the gate.

yes.

here's a tutorial from our very own MV tech video Mitch!

Ah, yeah, I was not taking about the regular bleed - I mean specifically pushing the fluid through with a syringe for the reverse bleed. I watched that video and the one by Robot.

Robot has a video using suction and I did not see him squeeze the lever while he was doing it, which is why I asked, since, in the procedure suggested by the person to whom I replied I would be pushing fluid into the line.

I tried the syringe suction the first time and it bled, but I thought it was weird I didn't have to press the lever.

The last two times I went through the laborious process of:
Open valve, stand, squeeze lever, fasten Velcro strap to keep lever open, bend, tighten valve, stand, release lever, bend, open valve - rinse repeat for about 20 minutes.

honestly, I don't know what to tell you. without being there and putting hands on the bleeder it's hard to say. it looks okay, but there's no telling without physical inspection.

you might try a different approach on the bleeding process. if you're not familiar with it, having a friend that is and can help would be a tremendous asset.

I don't know if I'd go reverse bleed on the rear caliper. that's a loooonnnggg run back to the master.

Don't know how well this works on ABS brakes but you just feed the fluid in from the bottom end and the air comes out the top. No need to squeeze the brake lever. works well on roll lock hydraulics as well .

Thank you for all the suggestions and ideas. Unfortunately, I just moved states and know precisely 3 people, none of whom know how to do this kind of work.

I will try a reverse bleed this weekend, and if that doesn't get all the air out, I will order the replacement rear caliper. I don't have a garage so I am at the mercy of the weather so I hope I can get this fixed soon - next two weekends look promising for me, weather-wise.

Thank goodness for Modern Vespa and YouTube!

it's unlikely that your rear caliper is the problem.

to loop back, you previous had posted this: nowhere in here do I see "topping up the master cylinder".

again, I think it's down to the process that's hanging you up.

you don't really need somebody that's well versed in mechanics to help you bleed the system down so long as you're doing it correctly, and from your account, that does not seem correct to me and likely to introduce air into the system further exacerbating the situation and frustrating you.

do you have any other "bleeding equipment" besides whatever syringe it is?

where are you in TN?

Northeast of Nashville

I will amend my process write up…
Open valve - squeeze lever & fasten Velcro strap to keep lever open - tighten valve - release lever - open valve - squeeze lever - fasten Velcro strap to keep lever open - tighten valve
look at reservoir to make sure the level was okay, top off long before it ran dry

I can only estimate as I was not closely measuring, but I would guess I pushed 120cc of fluid through on Sunday. I had to stop when I used the last of my bottle.

Equipment is limited. The bleed I did on Sunday used:
Wrench for valve
fresh hose for drain
container to drain into
60cc syringe to carefully refill the reservoir
Dot4 brake fluid
velcro strap to fasten the brake lever
rags to mop up

When I tried Robots suction method I also used a 2nd syringe attached to drain hose to just suck the fluid out and did not squeeze the brake lever but did top off the fluid as needed.

I had a similarly squishy brake for a long time on my GTS. What worked for me was to hold the brake lever tightly engaged with a velcro strap, leaving the reservoir cover off over two days/nights. What ever tiny air bubbles were trapped in the line eventually bubbled to the top and out, and the problem went away.

a bit far to come my way then

I don't think this is your problem but humor me and take a look behind your muffler and tell me if you see this back there.

I did see leaving the brake depressed after a bleed for 24 hours suggested elsewhere, worth a try!

The air here is moist, I don't know if that might corrupt the fluid? I would put the scooter cover on, of course.

Aw, you are kind to consider letting me visit & helping in person ! Are you in eastern TN? I would prefer to be closer to the mountains, even though this area is pretty.

As an aside, no brake line lasts forever. If original, these lines are 15 years old. That's old, especially if the fluid hasn't been replaced as often as it should. In my experience, almost nobody replaces brake fluid as often as they're supposed to, and most people don't do anything until their brakes stop working. (Ditto fork service.) I bleed brakes (often with syringes) every day.

yes about 25 miles west of knoxville, 65 miles from the bottom of the dragon.
Exit 352 on I-40

I may be wrong here but you say that your sequence is: open valve, then you squeeze lever. Shouldn't you be pumping/squeezing the brake lever, holding it in and then opening the bleeder till it bottoms out while fluid runs into your bottle , keep it bottomed then close the bleeder. Once closed release the brake and repeat the pump, open, hold and close sequence?

Good catch. I read his post twice and still totally missed that.

1) Squeeze lever, squeeze lever, squeeze lever... HOLD IT SQUEEZED.

2) Open valve, fluid comes out, close valve, release lever.

3) Check fluid level in reservoir, top up if necessary, begin again.

Brake fluid should be new and from a unopened fresh bottle. If you are using some half used bottle from 2 years ago it might contain some water.

saw in another thread about using teflon tape on the nipples ...

I wondered if I could wrap the threads. I wasn't sure if it would disintegrate. I will go ahead and try it to tighten up the threads.

Wrap up.

The tips were all really helpful, most of all, I think, to pump the brakes. I sent another 120cc of fluid through and the rear brake is much better, I think there is still air, but it has been reliability functional.

I will go another round this coming weekend, to see if I can get them firmer. Brake fluid bottle #4 from the auto parts store was enormous so I have plenty of fluid to do this (hopefully) final round.

Thank you for all the help!