Modern Vespa

I understand that many of my threads of recent are related to my scoots brakes and I understand if many of you are bored, but I just can't seem to resolve the issue.

Basically a few weeks ago my rear brake pads were replaced by my dealer and Since then, the brake has been spongy. Obviously my first port of call was a brake bleed - nothing. Then I phoned around some dealers and they either said air is still in the line or they'd want money before telling me anything. So with that I decided to bleed the line, but this time completely flush the line with a litre of brake fluid - nothing!

So last week after some more researching (if you could call it that) I bought a torque wrench, breaker bar and some copper grease (all of which will be coming tomorrow) and plan on sliding the wheel over to allow me to remove the calliper to check inside giving it a good clean if necessary (even though it's less than a year old)

Right now i'm sat here at 10:14pm covered in crap pumping another 500ml of brake fluid through the line.

So I was wondering if anyone has any suggestions? I've bought a mityvac - no luck, and now i'm at breaking point as my operation on my spine is getting ever closer and i'd like a decent ride before my 1-2 month recovery.

Thanks!

My only suggestion is that when you have the caliper removed, do NOT attempt to pump it outward with the brake handle. If you do so, the internal seal will come into contact with an area of the cylinder that it has not touched before, and it will pick up dirt. After reassembly, the dirt will chew through the seals in a couple of weeks of normal use, leaking brake fluid all over the disk.

I believe there was another recent thread about soft brakes here on MV.

Cheers and good luck,
Bob

The MityVac should have done the trick - especially if used in pressure mode to push fluid back towards the master cylinder. The GT and GTS models can have a very similar problem with spongy rear brakes unless reverse-bled. Same with MP3/Fuoco front brakes.

does that have a rubber section on the brake line ?, if so check to see if it is expanding when you pull the brake lever, may be time for a new line. if its an all steel line..... im stumped.

Ironically i checked for line expansion before checking this thread and found nothing. The line seems to be steel line though I could be wrong.

At a guess It seems like either some sort of valve failure/fault which allows the pads/pistons to compensate for pad wear or salt and much around the pistons.

Piaggio brake lines all tend to be braided. Not the best quality, but good enough. I know a couple of people who swore by changing out the lines, but the mech I spoke to who did the work says they're hardly any different when not viewed through a purchaser's eyes.

Check the seal in the master cylinder as well. I know it is pretty new, but if the seal has a nick it will give you the same mushy feeling.

I just bled all the hydraulics on my MP3. Wasn't looking forward to it as I have read so much about the problems. I bought a Mityvac, but just couldn't get on with it.

I read somewhere that gravity is my friend (relief - didn't think I had any friends riding scooters in a predominantly motorcycle-populated area). I discovered what this meant - air will rise as the fluid it is suspended in reacts, as it must, to gravity. I found this method REALLY successful and it worked like a charm:

1. Remove the bleed nipples and wrap the threads in PTFE tape (stops air leaking past).

2. Get a large Syringe. I know a nurse who got me a 50ml one, although I bought a 150ml from ebay for a few pounds.

3. Buy some length of clear plastic tube to fit between the nipple and syringe (easy to find at B&Q or hardware store - take the nipple/syringe with you to size). Do not use silicone tube, it kinks/slips off too easily.

4. Some people suggest leaving whatever (usually dirty) fluid is already in the brake lines. This has the benefit of not introducing new air into the system. In this case soak up most of the dirty fluid visible in the master cylinder, being careful not to remove all of it. I used a spare syringe, although a bit of tissue paper would have done just as well. In my case I had removed all front hydraulics (to renew steering bearings) and so these were in a clean, empty state. However while I was doing the front I decided to renew the rear lines fluid and just completely drained it.

5. Pack a few pieces of rag around the master cylinder to soak up any spillage.

6. Draw up the brake fluid slowly. When the syringe is almost full hold by the tube, open end pointing towards the sky and the syringe hanging below. Gently flick the side of the syringe/tube with your finger to dislodge air bubbles. Repeat this a few times, moving the plunger until all the air is dislodged and the tube is full - except for an inevitable small amount right at the open end of the tube. Ignore this small amount for now. Connect the end of the tube to the bleed nipple. Now hold the syringe as high as you can to extend the tube and repeat the 'finger flicking' to dislodge the air that was left in the open end of the tube (mentioned earlier). You may also need to gently withdraw the plunger to pull the air bubble(s) through the tube and into the syringe. It takes a moment to rid the line of all air.

7. I find it helpful to fix a bungee strap so I have something to suspend the syringe from when I am opening or closing the bleed nipple.

8. Open the bleed valve half/two thirds turn and slowly force the plunger into the syringe. At this stage keep a close eye on the master cylinder. Either you will need to withdraw dirty fluid being forced through or in any case you need to make sure you do not overfill and spill.

9. Close off the bleed nipple.

!0. Pack away all your stuff. Put the kettle on and enjoy a cup of tea!

I had an immediate 100% success with the front end, apparently the troublesome end on an MP3! The rear brake lever was a little spongy. I took the master cylinder cover off and covered it with a piece of tissue and tied back the handlebar lever overnight. Next morning it was perfect. Some claim leaving the lever pulled in overnight doesn't work. I can only report my own experience - it does!

The following day I MOT'd the bike and took it for a test ride. New tyres, new bearings, new brake fluid - Perfect!!

Good luck.

Awesome brake bleed write up man

EDIT: Sorry I slightly misread the thread thinking that it referred to an MP3. I'll leave the rest because the general principles may still be useful.

An important factor here is that the pads were changed but apparently the brake fluid and hydraulic system was untouched. If this is true then the fault could not be caused by air in the system. The one horrible exception to this is if a truly hamfisted mechanic blew out a piston while the pads were out and then didn't bleed through properly.

So first I would look for mechanical problems with the caliper and/or pads. The caliper should float on its mounts to self align so that both pads apply equal force to the disk. If you grasp the caliper it should be reasonably free to rock on its mounts then when you apply the brake it should find its natural position and stay there. Look for movement as you apply the brake to see if it is flexing in an odd way then springing back. Also make sure that there is no movement of the disk or wheel which might suggest incorrect assembly.

When you dismantle the right hand support bracket make a careful note of where the washers and spacers are and make sure it corresponds to the positions shown in workshop manual and/or parts book. It has been known for these to be assembled incorrectly.

Finally when you have removed the caliper you will be able to see if there is any fault in installation of the pads. Also make sure that the caliper moves in and out on its mounts. Spray some silicon grease under the rubber bellows if necessary.

If nothing is found and you do have to bleed the system again clean up the area around the piston seals then force the pistons back into the caliper until they are flush with the caliper surface and use a wooden wedge to keep them there when you bleed the system.

Regards Roadster

Wow! Looks like i've got an intense day ahead of me then.

Cheers for that guys, i appreciate it. I'll update later with any progress. 8)


I owe you all a pint!

Not sure if this is of interest to anyone, but here's an update.

I've tried everything suggested on this thread. Yesterday last night the pressure increased nicely and so this morning I had a check and...spongy brakes again!

Gave my dealer a bell and he said he'll get them checked out under waranty and most likely replace the caliper and master cylinder (touch). So just need to arrange a pick up with AA next week.

2.5L of brake fluid used in total now.

questions:

1. Is it safe to use acf-50 inside brake calipers to disolve salt etc?

2. How much copper slip should there be on the back of brake pads?

Cheers guys.

1. Not inside the caliper, no, and how on earth did salt get in there?

2. Just the thinnest of smears.