Modern Vespa

Hi,
I have a leaky Rear master brake Cylinder 2nd one in 2 years. errrr...
I can't find a new one for the GTV. I have exhausted all my resources.

Next step is to attempt a rebuild. Has anyone on the forum have experience rebuilding these Heng Tong MC's?

If anyone has, can you tell me what is the most compatible kits for this? I read somewhere that the Heng Tong has a 12.7MM seal size?
Not sure if I can just look that up and order.

Any advice suggestions would be greatly appreciated.

Put some radial on it

That may have to be the final solution. The issue is I don't want to spend 200.00 for a rear MC. Because I would have to purchase the front as well.

That setup does look nice, I will give you that.

But I Think all masters that are used on a Vespa will fit or a clutch master from a ducati or other brand with a hydrolic clutch the are 12 mm

I took apart my old MC and tried to fit it with a new Oring.
The plunger ( For lack of better name) with a 2mm thick Oring would not work even all greased up it would not slide into the chamber. I tried a 1.5MM and I felt it was too Thin. Tonight I am going hunting for a 1.7, 1.8, 1.9mm One of these will fit. The spring appears to be in great shape, and the Hood at the tip of the plunger appears to be in good shape.

I don't know much about the Mechanics of the Brake Master Cylinders, but what I have been able to learn is the Hood at the tip of the plunger pushes the Dot4 into the line and builds the pressure. The Oring prevents the Dot4 from escaping the chamber and keeps the Dot4 in the chamber. there is a washer and a snap ring and a rubber dust cap which keep everything in place.

I believe I am on the right track, I will try to figure out which rebuild kit to order. I have a couple coming from Amazon tomorrow, they were cheap, and I am hoping one of them will fit, or i will be happy to mix and match.

It appears that Piaggio has discontinued all the chrome master cylinders. We just got the new one for the LXV, and it went from being all chrome to this:

Hi Motovista,
Hope all is well. The pic of the one you posted is the new replacement MC for the pre ABS GTV bikes?

I will order some if they are, Astatically the chrome ones get all pitted and stained over time. So black just might look better.
Thanks
G

For those keeping score:
I received the 12.7MM rebuild kit attempted to install and learned it was too large for the bore size. I greased and lubed as much as I could, it was Like a Great Dane mounting a Chihuahua, no matter how I tried it was not going to fit.

This morning I reluctantly ordered an 11MM rebuild kit, it appears to be the next size down. We shall see, I have a feeling the 11mm is going to be too small. But for the price this experiment is worth the education. I will receive the kit on Saturday, will try to install and update.

These GTV's are a nightmare with certain parts.

Cm074901 and CM074801 are likely the best ones for the GTV. They are the GTS versions of what you have now. About $120 for the pair, less the perpetual Cannonball Alumni discount. And with the savings from the Cannonballer discount, you can buy a nice big can of silver paint.

https://scooterpartsco.com/300-piaggio-c-801_836/brake-master-cylinder-rear-for-vespa-gt-gts-p-9006.html

https://scooterpartsco.com/300-piaggio-c-801_836/brake-master-cylinder-for-vespa-front-p-22824.html

You sold me on it. Just ordered front and Rear.
So the Original Silver rear MC is an 11 MM diameter, smaller than what is in the GTS. I took a GTS brake MC apart and thought I could just swap them, but that was not the case. The GTS is a 12.7 MM interesting they went to different sizes for the GTV.

Anyways, I am not to concerned about appearances, so no Spray Pain necessary