Modern Vespa

Hey everyone,

I'm in desperate need of some guidance for my rear ABS brakes.

For context: I just replaced the immobiliser antenna on my bike because if been having intermittent issues with it that got worse when summer hit. 230€ just for the part.

The next day rolled my GTS out of the garage and started it up and noticed that I couldn't depress the lever to the rear ABS brakes. My immediate thought was WTF have I done now?!

But I had already dismantled the rear panel to the leg guards twice without issue. And I'm assuming it's just a coincidence.

So, basically what is happening now is that when I start the engine, it seems fine. Then as soon as I use the accelerator I go to squeeze the left lever, it's super stiff and I have to squeeze it super hard to get the first use out of it and then everything seems fine from there.

I took it to an all-make garage who said it's the ABS central unit that's faulty. Then I went to Vespa dealership where I bought it and he only took the time listen to me and tell me he'd never heard of such a problem and refused to even give it a try, which really annoyed me because I've had nothing but problems with it since I bought it brand new 5 years ago and this is how they treat me. (I'm not a pain, I swear… I'm probably too nice with them actually)

I then went to chat GPT that indicates it may be a problem with the brake booster/vacuum system. But I can't find much more about this issue.

Does anyone have any ideas?

Thanks!

To understand: does the behavior of the brake change before/after starting the engine? So you can operate it normally as long as the engine is off and only after the start / the first acceleration the problem occurs?

Can you turn the rear wheel freely by hand (when she is on the stand and the left brake lever cannot be pulled)?

When did you last change brake fluid?

Hi, I had the exact same problem earlier this year with the rear brake lever of my 2018 GTS 300. The problem occurred out of the blue: stiff lever upon starting, no problem after a hard squeeze for the rest of each ride.
What helped for me was a brake fluid flush, easy job which can be done in 20 min. Plenty of videos available on YouTube. I flushed about 200 mls, half a bottle of dot 4, which seems to have fixed it. No problem after that. Take precautions not to spill any of the fluid on the chassis as it will stain paint or plastic parts.
Keep us posted on how it goes.

Cheers, Holx

I have a 2020 GTS HPE and I had one stiff level one ride, and two months later - I couldn't use the rear (left) brake - it was frozen. Scooterwest (Robot) coordinated the service (rode bike in about 10 minutes away) - and I had option to drain and refill (flush) the brake fluid (what I did) or merely bleed the brakes. The first option is what I did and it was perfect - no problem since. If it happens again, I am thinking it's time for ABS to be replaced (and by the way, I was two weeks out of warranty or so!). It's been six months or so and I feel pretty lucky.

Hey! Thanks for the reply.

The problem occurs only after each start up and 90% of the time only after I've used the accelerator.

Once I accelerate I have to squeeze the left lever really hard. Once I've done that I don't normally have any problems.

The wheel turns freely. I usually roll my Vespa in reverse out of my garage with the engine off. Then I start the engine, hit the gas and have the problem.

When the engine is off, the lever works fine (or at least I haven't noticed any problems so far!).

I'm going to try to flush the brakes today and I'll keep you posted!

Thanks Holx! If this saves me 1000€ I'll buy you a drink! I'll be giving this a try this afternoon. I bought a drain kit for the rear brakes last night. I'll keep you posted!

So I tried flushing the brakes. Same issue. It feels slightly different.

Something I noticed while I was pumping the brake fluid is it seemed sometimes tiny bubbles were coming back up. I kept filling and pumping until I couldn't see any more bubbles floating up. Maybe I was pumping too hard, but I'd didn't let it go dry.

If there was an improvement, percentage-wise, I'd say 20%. Maybe it was a little harder to get the first brake pump before.

What's annoying is that the brakes will work fine after that first pump… I don't get it!

Anyone have any other clues?

I had basically the same problem on my 2020 GTS late last year. It started 2 weeks after my warranty expired. Long story short...it was the ABS unit. Piaggio covered the replacement cost.

They seem to be well aware of the ABS pump problem. There are also a few threads on here about the ABS. Do a search for stiff or stuck brake lever.

Hi just reading your issues.
I have a 2018 gts,had to replace the immobiliser antenna last year.Now having issues with both front and rear leavers being super hard to pull on first pulling away after starting. I've not resolved my issue yet as have been away but will read how you got on with interest.
All seems a bit coincidental to be.I recon Vespa have an issue.

Hey Guys,

My problem went away spontaneously like 2 days ago. I don't know if it's from taking speed bumps at 50km/h that shook an air bubble loose? There are speed bumps everywhere in France.

I haven't done anything different other than abuse the Vespa a bit.

I contacted Vespa customer service and they told me to take it to a dealer for a diagnostic, which I wasn't keen on doing and having to pay and arm and a leg to just say no to a repair.

I've heard the 2019 and 2020 models had a recall on the ABS pump. I can't find anything about the 2017 models.

I'll report back if it starts acting up again. I'll see what happens when I take it in for its routine maintenance.

doubt it. If you had an air bubble before or after than it would have felt spongy then.

I thrash my bike along on terrible unsealed roads with potholes, rocks and corrugations very frequently and never had this hard brake lever problem. Hard enough that I destroyed my steering bearings.