Modern Vespa

Ok I'm not sure how much information to include here so I'm just gonna start from the beginning.

I recently replaced the fork seals on my fly 150 and after reassembling the front end now I'm having an issue with my brakes, I tried the brake fluid change procedure from Mitch's repair videos, did exactly what he did, for HOURS but no brake pressure, fluid dribbles out the brake drain valve a drop or two at a time or not at all, it's new fluid too at this point with some air bubbles also but no pressure in the brake grip?

I also noticed there's a small hole in this rubber piece on the master cylinder where the grip contacts it and pushes it in,




Could this hole in that rubber piece be the cause the brakes not having pressure or could it be something else?

Maybe disassembling the master cylinder damaged it in some way? It is a little bit corroded and had a stripped screw that needed some work to get out.

My brakes worked fine before I replaced the forks, it probably is the original master cylinder and who knows how long since the fluid had been replaced, not in the 2+ years since I've had it. I did pressure test the cylinder with the brake line off and it did create a bit of suction when my finger was placed over it, also tried clearing/pressure testing the line with an air compressor, it seemed ok, no noticeable air leaks or other wet spots anywhere that I could see.

I'm not sure what to do here, considering replacing the master cylinder but thought id run it by you guys before throwing parts at it.

Hmm, I guess I should have searched first,will have to try this next, scooter is in my friend's garage right now

ET4 1996 - front brake, no pressure

Could reverse/vacuum flushing be the answer here?

It's a forty dollar part, so if you need a new master cylinder, it's not the end of the world. But it could also be the caliper. Or the work.

The rubber piece is designed to keep water and crap out, because that damages the piston/plunger. If it's been torn a while, it hasn't done what it was supposed to, and there's a chance that's your issue.

What sometimes works, if you have a helper, si to take the caliper off the wheel, hold it as high as possible, with the bleed nipple facing up, and bleed them that way. If you can push the pads all the way back into the caliper first, and wedge something between them to hold them in place (old brake pads fit perfectly), there's less space for air to hide. Ideally, you would put the brake caliper in this position, figure out a way to leave it in that position that didn't involve you holding it for a couple of hours, and let any trapped air in the hose or caliper make it's way to the exit. Bungie cords are good for this,

That was the only way I could bleed the front brake system on my Baghira and the Ferando rear caliper on my GT200.

just an update, tried reverse flushing but it was no help, just ordered a new master cylinder, hopefully that fixes it, in the meantime, took apart the caliper and cleaned it out, wondering about the line at this point too? not sure how all of sudden i'm having brake issues just from draining the fluid when i had none before, thought for sure it had to be air in the system. I just get this feeling that there's something i'm missing here.

Are you near Sutter Creek?

Yes in fact my scooter is parked at my friend's garage in Sutter Hill and I live in Jackson

I'm only mentioning this because I can feel your frustration. I have a lot of experience with BV250's, and I have an ongoing problem with a front brake that always feels a little spongy. It stops me, but not real well. I've bled it several times. Somewhere I read that I should try squeezing the handle hard and then securing it with a zip tie, overnight. I did that and in the morning it was better. Not completely better, but better. Who knows why. It's still that much better, but still not cured.

got a new master cylinder on there and also cleaned out the calipers and reseated everything and the brakes are now holding pressure, it doesn't quite feel like it did before, but it's certainly ride-able, might try another inverse bleed and maybe tie off the lever over night see if it improves further.