Modern Vespa

When I bought my scooter used it was soft to squeeze the brake, and when serviced they replaced the Rear Master Cylinder (Part # CM074801), ie the rear brake leaver. It made it tighter but not 100% and I think it's getting softer. They topped up the brake fluid, it didn't seem to be empty at the time, but said their might be a bulge in the brake line, or something causing it to have less pressure.

I've read that replacing the brake line is a pain in the ass because all the body needs to be pulled off. Is there a way to inspect the line without pulling off all the body? Or should I just go ahead and order the part so I can replace is while I check?

I imagine I'll need part # 667312 Rear brake hydraulic piping, and brake fluid?

Before you go down the road of changing the brake line. Try bleeding the brakes again so that you are sure there is no air in the lines, which is entirely possible with a master cylinder switch. When you are sure there is no air in the lines and you still have a soft brake then yeah, the next step would be to replace the brake line.

Did they flush the brake line, or stick a new master cylinder on and try to get the air bubbles out from the top?
I would first bleed the brakes, then consider the rear caliper, then maybe the brake line. In my experience, it's almost always the caliper, and not the master cylinder, that makes the system "soft".
There is nothing about the line, in terms of how the brake system works, that should cause it to have less pressure over time, especially if that time is a couple of weeks. If there's a hole in the line, you will see brake fluid.
Make sure you use DOT 4 fluid, and not DOT 3.

You could also try turning the handlebars to level the bad master cylinder, squeezing the weak lever and then wrapping it overnight. Seems like a snake oil cure, but sometimes it's enough to let some residual bubbles work their way out the top. I've had it work several times when nothing else did.

Thank you all for the input. I'll try the snake oil option first.... then flush the brake line and if that doesn't work, change it.

I'd check that rear caliper too before changing the brake line as Motovista said it's often the culprit.

take one of your viagra pills and crush it up really fine, open the brake resivor and only put in 1/2 the amount. this should get the brakes hard enough for you. if not dump in the remaining amount, but beware this will only last 3-4 hrs. anything longer call your nearest scooter mechanic immediately.