ScootRS Lambretta Hydraulic Front Disk Brake installation

UPDATE 2005: There's a new version of the disc which uses Japanese Nissin hydraulic components or a cheap upgrade for the old kit.
Pros  Cons 
Kit is complete, castings are good quality and the whole solution is well engineered  Can't use wide wheel rims. You can use semi-wide if you grind off some metal from the caliper.
Good  price  Supplied hose bulky. Change to Goodridge 900mm (B30900CL) ~30 No performance improvement, looks trick. I recommend ScooterLoopy, although other dealers sell the Goodridge Build-a-line kits.
Great upgrade for shitty Lambretta brakes (even the original disk brake) Handlebar casting holes didn't line up - I've been assured this is a one-off as all are checked on a jig.
Great customer service and backup from ScootRS Brake piston seal leaked - ScootRS exchanged the entire caliper, still leaks and goes soft after 2 weeks!
Looks factory fitted Steel plate that holds caliper to disk seems to be pissed and hence brake pads wear unevenly

Time to install - ~ 2 hours, then 1.5 to change the caliper!

Here's part of the kit with the hub (innocenti), including the speedometer drive mechanism, disk and caliper. Another standard size wheel rim found and fitted. Throw away the hardware supplied and fit stainless with spring washers.
Remove the front brake side handle bar grip, front brake lever/cable and the light/horn switch housing. Note the plate that holds the caliper in place with the disc.
Disconnect the light/horn wires from the headlight and remove the entire switch. Then take out the 2 screws holding the casing to the handlebar and slide this off. Here are two types of plate, one for fork links, the bottom one (fitted) is for disk links i.e. SX/GP/TV200/TV175.
Now fit the complete superb replacement casting that houses the brake fluid master cylinder, lovely bit of kit! To fit the assembled hub offer up the bolt fitted to the plate to the disk link
Shame the screw holes don't line up though! Slot in the the axle, fit the washer and bolt and tighten. Mind the grease nipple on the hub, I smashed mine off during fitting!  
Now remove the existing front hub. With disk links remove the main axle nuts first and lift out the washer ... That's the easy part, back to the headset feed the hydraulic hose through the horn casting down through the headset and horn casting to the brake caliper. 
... repeat on the other side.   Now line it up in order to drill a hole in the headset base for the hydraulic hose. 
Now loosen the main nut on the speedo drive side and ...  If using Goodridge hose fit a stainless steel angle connectors (BK599-03C & BK594-03C needed)* Line this up with where the hose would naturally go into the headset base. Note the death crack in my headset coming off of a slot made in the past! It's better to drill a hole than make a slot, it's stronger apparently. 
... the hub should drop down and out.   With Goodridge hose drill a 13-14mm hole. The supplied rubber hose will need something much bigger.  
Unfortunately I found with wide rims that the caliper presses right against the rim and the wheel won't rotate. Semi wide rims are apparently OK if you grind off some of the caliper! Thread the hose through the hole, connect and tighten everything up and fit a rubber grommet around the hose where it enters the headset base.  

*If your upgrading the hose to a Goodridge on a ScootRS bike that already has a hydraulic front brake installed the stainless connecters are different.

... next a bodgers guide to bleeding and filling a Lambretta hydraulic brake system