Modern Vespa

Lx150 - just replaced the brake line with a aftermarket hose. I can't seem to bleed it. I have done plenty of brake bleeding in the past but never replaced a whole line before. I suspect the master cylinder but as I used a 10mm aftermarket brake hose could that be the issue?

I see some pathetic effort to pump a little fluid to the caliper but not the pressurised flow I expected.

so I checked the hole inside the banjo fitting on the new hose and compared that to the old- same. I then disconnected the master cylinder - put some fluid in it and squeezed the handle- nothing. If I take the handle off and give the plunger full movement it works. New master cylinder ordered but I'm going to try an after market unit first. 240 australian dollars for a genuine is nuts.

Yeah, fairly common.

What happens is that as brake fluid is hydrophilic you get a line of corrosion in the master cylinder bore right at the end of the normal stroke.

When you attempt to bleed the lever now goes past this point to the bar and the rubber seal is damaged by the corroded bore. Why pressure bleeding is preferred method of professionals.

Can be prevented to an extent by regular flushing of the system not allowing corrosion to form. Recommended interval is every 2 years.

OK so I'm trying a knockoff master cylinder with a cherry switch instead of the vespa brake switch. I hate hacking harnesses so made this as an adapter using an old broken vespa brake switch
That way if someone ever fits a genuine master cylinder later they can revert to the standard switch