Modern Vespa

Hi there -

I botched up a broken mirror with a stuck screw (Left Hand). I tried a helicoil and got nowhere, so ended up just ordering a new master cylinder. The bike it about to be sold so I want it to be in good condition.

I can't find anywhere on MV that details how to replace the master cylinder. Anyone know of any Wiki posts or Forum threads that would guide me through this process?

I figure I'll replace the brake fluid and bleed the brakes while I'm in there on one side anyways.


Thanks!

Hi,
Take the handlebar cowls off as described in wiki , then remove the master cylinder cap 2 x no2 Philips machine screws and siphon out the brake fluid using a syringe, then undo the 17mm banjo bolt on the master cylinder,remove and make sure you don't lose the two copper sealing washers. have a plastic bag and tape handy to wrap the hose end so no debris enter the hose and fluid doesn't spill onto the paintwork.
The master cylinder is bolted onto the handlebar with 2 x 4mm Allen head bolts, undo and remove.
Re fitting is the reverse of the above except the master cylinder is located on the handlebar by means of a locating dowel positioned inside the clamping collar and a hole in the handlebar.
Cheers Andy

You could save yourself some aggravation by clamping the flexible brake line rather than bleeding the entire system. Purpose made tools usually have two rods linked together at one end and with a thumb screw at the other which squeezes the rods together. If you connect and fill the new master cylinder then raise it vertically and tap the banjo area any air bubbles should rise out through the open port. If successful the lever should feel completely solid before you remove the clamp.

Watch out for fluid squirting from the port if the lid not in place when you operate the lever.

Perfect! Thanks for the detailed yet simple response.

Done and done!!