Oiltek ali Lambretta Super-Light | RETRO TECH

What’s so special about it?

Super-light aluminium Lambretta: when carbon bodywork is just not light enough! It’s a custom built scooter with a box-section aluminium frame for superb power-to-weight-ratio: the Olitek Ali-Bretta.

At the VFM custom show in Whitby we spotted quite a unique entry and just felt we had to take a few snap shots of it. With a physiognomy of a full panel work street racer Lambretta it didn’t stand out at first glance but on closer inspection revealed it features a handmade chassis. It was built by Paul Gillow as a showcase for the products and services of his company Oiltek Ltd.

Paul could have also christened his creation ‘Super-Light’ because that’s exactly what it is. With an aluminium box-section frame and fiberglass bodywork this scooter enters the ring in the flyweight class, weighing in at just 87 kilos. The TIG welding was done by John Beck and is a work of art; you could inspect any inch of the seams and would probably count the same number of uniformed ripples on each of them.

It’s easy to walk past a scooter like this without appreciating the trick bits within.

The advantage of weldable aluminium is, it is three times lighter than steel. On the downside it only has a third of its stability. Subsequently, the loss in strength needs to be compensated in stressed areas. This is why a tube was welded into the frame holding a machined high tensile bolt as the rear suspension mounting – incidentally, damping is enhanced by BGM shock absorbers front and rear. The sections around the manufactured engine bar tube and brake pedal pin were reinforced and the tubular steering column was reworked to accept Lambretta steering cups for the shortened Li fork.

GRP in Leicester laminated the bodywork out of fiberglass, except for the refined horncasting and the short rear runners made by Oiltek. All electrical components are nicely tucked away behind an ali cover. Tightly between this cover and the rear of the frame sits the ali tank – also John’s work – it supports the fibreglass seat arch under the rider’s weight.

Quite a unique touch is the modified Li Special headset that has been altered to take a round SIP speedo for Series 2 models. Stopping power at the front is delivered via a fully-hydraulic braking system with an outboard disc by Scoot RS while the rear is sporting Oiltek’s own set up, something special indeed. It is cable operated from the pedal to the master cylinder that is mounted on an ali torque bar. The latter is suspended between a machined ali clip over the engine mount and a twin pot caliper that is held by a nicely crafted bearing supported ali plate. Does the world really need something like this? No. But don’t we all love a bit of scooter porn?

The engine was built by Paul, using Lambretta small block cases with welded and re-profiled transfers. Trick bits include an AF RB 200 barrel ported by Martin Cook of Chiselspeed Tuning, a 60 mm Tameni crank with Yamaha rod, a 35mm Mikuni carb on a LTH reed block with AF reeds and a Franspeed Race pipe. The transmission operates via a 19/46 primary drive, LTH 7-plate clutch and a close ratio gearbox using Italian GP 150 1st-3rd gears and a DRT 4th gear.

This configuration produces 28bhp at the rear wheel, which is roughly four times the power output of a standard GP 150 Lambretta engine. If that sounds impressive wait for the power-to-weight-ratio; 17.1kg/bhp (on a standard GP 150 weighing 120 kg) compared to 3.1 kg/bhp – physical laws of mass and inertia indicate this thing will be very quick off the mark! However, should you also decide on a lightweight scooter that’s been raised on amphetamine based diet pills make sure you never miss a Weightwatchers meeting as this would be defeating the point…

Words and photos by Marcus

Specifications

Owners name: Paul Gillow, Oiltek Ltd.

Town: Barnsley, South Yorkshire

Scooter name & model: Oiltek Ali-Bretta – custom built chassis to Lambretta GP geometry

Year: Autumn 2015

Engine details: Modified Li 150 cases, AF Rayspeed RB 200 barrel ported by Martin Cook of Chiselspeed Tuning, LTH inlet manifold, AF reeds, Mikuni TMX 35 carb, Franspeed Race exhaust with SIP end can, crankshaft using Tameni webs for 60 mm stroke and 115 mm Yamaha con-rod, 19/46 primary drive, Regina 82 link chain, LTH 7-plate clutch using Honda plates, close ratio gearbox using Italian GP 150 1st-3rd gears and DRT 4th gear, all cowlings made from fiberglass by GRP. Built by Paul

Power output: 28 bhp

Paintwork: By Mark Brown

Frame/fabrication: Aluminium TIG welded box section frame with tubular front section machined to accept Lambretta steering cups and bearings for forks. Machined tube for engine bar welded to frame. Mix of square and round bars machined and welded to frame retaining pivot for rear brake pedal. Tube welded into frame holding machined 30 mm high tensile bolt as rear suspension mounting (i.e. mounting replaceable if necessary). Weight: 9kg. TIG welding by aluminium specialist John Beck.

Forks: Lambretta Li shortened to GP length.

Wheels: SIP tubeless rims with tyres

Suspension: BGM shock absorbers front & rear

Headset: Li Special, headset top machined out, self-manufactured aluminium ring welded to it to accept SIP Series 2 speedo and clamped into position with Series 1 bezel.

Tank: Aluminium TIG welded (capacity 7 litres) designed to support the seat arch, Lambretta hi-flow fuel tap

Electrics: Hidden behind ali cover in front of tank, incl. CDI, advance/retard unit, regulator

Front brake: Fully hydraulic set up by Scoot RS with outboard disc and floating caliper

Rear brake: Semi-hydraulic system by Oiltek consisting of ali mounting clip over engine mount, ali torque bar carrying Righetti Ridolphi master cylinder – cable operated via brake pedal. Short Venhill brake line connected to twin-pot caliper held by machined and bearing supported ali plate (more details on that to come).

Bodywork: Legshield, panels, bridge piece and seat arch made from fibreglass by GRP in Leicester. Short rear runner boards are an ali version of the mild steel ones by Oiltek. GP horncasting with SX grill welded to it and smoothed.

Seat: TSR