Feature Scooter: Crankcase Induction Avanti 240
Aspirations and ambitions, everyone has them… a hope that one day that special yearning becomes a reality. For this scooter owner, that dream finally came true!
Aspirations and ambitions, everyone has them… and for this scooter owner, that dream finally came true! A sublime Avanti 240 with crankcase induction is the result.
Bruce Macpherson was a typical Eighties Scooterboy and, like many of his contemporaries from all over the UK, he was armed with a minimal budget, not much in the way of mechanical know-how, but huge bagfuls of enthusiasm! He regularly traversed Britain, attending many of the national scooter rallies, often astride a machine which offered not much more than a 50-50 chance of completing the round trip without breaking down. A change in personal circumstances during '86, coupled with swapping his electronic GP (fitted with a Honda 205 top end) for a Kawasaki motocrosser the following year was the start of what became a 25-year hiatus from the scooter scene. Throughout that quarter of a century Bruce, in his mind, often revisited the promise he made to himself as a young Scooterboy which was that one day he would build himself his dream scooter. The steed he never had the money or ability, in terms of engineering skills, to build during the Eighties. Finally realising that dream became an evolutionary process which spanned nine years to reach its final incarnation, with several compromises alongside more than a few revisitations on the journey to finally achieving his self-set targets for his ultimate scooter specifications.
Daydream believer
On his eventual return to the world of scooters, around a decade ago, Bruce bought a rusty, rotten in places, but just about running GP125. He set about giving it something of a rebuild using Sticky's Complete Spanners manual as a guide, along with a recently obtained socket set and his determination to succeed. “The engine turned out to be a very tired Mark Broadhurst 205 conversion on a Spanish Lambretta 200 casing. I gave the scooter and engine a complete strip-down and rebuild, spending much of the two years in my shed. That rebuilt engine would eventually go on to become the first running unit in my dream scooter. I was immensely proud of my achievement, having done all the work, bar painting, myself. That GP turned out pretty well, however it wasn't the scooter I'd had in my head for so many years. Ideally, it had to be the same vintage as me, November 1964.” As all Innocenti anoraks will know, Bruce's self-imposed narrow timeline of manufacture for his dream Lambretta limited him to a choice between Series 3 models of Li125, Li150 and TV175. The TV/GT200 just missed the November '64 requirement by a month, with the first examples of that model going into production in December, with a mere handful only made in that month. Variants of the Li models were produced during Bruce's birth year, the Golden and Silver Special. For some two years, he searched to no avail, drawing a blank on sourcing a Lambretta made in the last few months of '64. Then in early 2014, he spotted an advert for an incomplete, unregistered Li150, being offered by, of all places, an auction house in Yorkshire. Cross-referencing a rubbing taken of the frame number with British Lambretta Archive revealed the incomplete Li would've been made in Milan during the middle part as opposed to the end of 1964. After looking for more than two years, Bruce, slightly compromising, decided that a scooter made during mid-'64 was close enough. A deal was done, in February 2014 he collected a Silver Special Li; well, the frame, forks, legshields, headset and horncast of said Lambretta.
Dreaming a dream
Pretty much from when he was a rally-going regular during the 80s, Bruce was taken by the dealer special Lambrettas from a decade or so before. Specifically, those with something of a racing heritage in their makeup, iconic machines such as those offered by Supertune, Royspeed and Arthur Francis S-Type. What particularly drew Bruce's attention was the combination of classic, timeless appearance with racetrackbred enhancements. While not wanting to replicate them directly, Bruce had in mind building a scooter that looked of its time, with improvements capable of coping with the demands of today's highways and byways. Specifically, a powerful, reliable engine that would deliver more than 20bhp, and that could comfortably cruise between 65 and 75mph when ridden on motorways in the UK. Additionally, with good, responsive acceleration for use on A and B roads, capable of passing cars safely at 50mph. It would need to be capable of long-distance touring with a decent fuel, oil and luggage capacity along with efficient brakes. While trawling the internet and viewing all manner of scooter photographs, Bruce spotted a couple of Rimini Scooter Centre retro-style race-inspired street Lambrettas, which became Bruce's primary visual inspirations. Armed with those requirements, Bruce embarked on the initial stages of building his dream machine.
Living the dream
Having researched thoroughly which items he wanted to upgrade and improve on from standard Innocenti '64 specifications, Bruce began sourcing and collating parts which met his specifications. An 18-litre capacity, bespoke (with a left-hand side cut out to allow the carburettor to sit correctly), long-distance fuel tank made from lasercut aluminium was obtained from Oiltek, courtesy of Paul Gillow. As the one-off tank occupied where a standard toolbox would have been, a fibreglass Nanucci legshield toolbox, to house the necessary tools, was found via a well-known internet auction site. To uprate the damping, braking and handling Bruce combined BMG engine mountings, along with BMG front shock absorbers, while the rear shock is an adjustable Readspeed item. This was in line with Bruce's intention to retain the classic appearance of a '64 Lambretta wherever possible. As was the hydraulic front brake too, which is an MB Scooters conversion to an SX front disc hub, along with a set of Broady (Mark Broadhurst) rebuilt forks, including stronger springs and fork links. Having been happy with the paintwork on the GP he had built on returning to the scene, Bruce commissioned SG Customs to provide a premium show grade paint job, consisting of a red and white combination accentuated with contrasting gloss black, evocative of a 60s two-tone paint scheme, but also an eye-catching scooter too. Equally, Bruce had similar improvements to the engine in mind. After narrowing down his choice of top end to a shortlist of four options, he settled on the TT3 225 Avanti, designed by Ron Moss. “I chose the Avanti for several reasons,
it's 30% bigger than other cylinders, with larger cooling fins and a bridged exhaust port. Port timings were quite conservative, producing power low down the rev range while offering a wide powerband, useful for high-speed touring on different kinds of roads. I also liked the pedigree and rarity of the kit.” To cope with an increased top-end grunt, a stronger AF Rayspeed 58/107 GP crankshaft was fitted, along with an RLC Cyclone five-speed gearbox with 18x46 primary drive cogs, plus a stronger MB Scooters layshaft. The engine casing was the Spanish 200 casing from the GP he built in 2011. Ignition set-up gave Bruce several choices, and he settled on a BMG stator with a lightened (by 200g) flywheel. The top end was given a mild tune by Chalkie at Replay, initially trying a Mikuni TMX 34mm, then a Dell'Orto PHBH 30mm carburettor, with a Franspeed race expansion pipe which, after 800 miles running in, initially delivered 20.5bhp on the dyno. Finishing touches included a pair of unique Avanti 5 Velocita (Italian for Advance 5 Speed) side panel badges, made from brass by a French jeweller. A bit of adjustment to the frame loop (removing 3mm) was required to give clearance to the larger finned Avanti TT3 top end. In May 2015, Bruce finally realised that dream of his, completing his ultimate scooter.
Make my dream a reality
From mid-2015, and the entirety of the following two years, Bruce enjoyed riding his dream machine to regional and national rallies as well as Lambretta Club members' rallies, clocking up more than 5500 miles. Bruce even picked up a trophy for his creation in 2016, at Night Owls scooter show, without realising he had entered! He felt an immense sense of pride and achievement every time he rode his creation, and not once did it let him down during that time. Although he didn't know it during those two-and-a-half years, his dream machine was the Mk1 version. During a chance telephone conversation with Ron Moss, the subject of discussion being Ron's latest Clubman exhaust system, the legendary scooter tuner mentioned a couple of engines he was working on for a customer. What grabbed Bruce's attention was when crankcase induction was mentioned. Always looking to be different, Bruce was hooked. Other changes from the Mk1 to the Mk2 version include a Casa layshaft, MB five-speed gearbox and a different side casing, plus Chalkie at Replay applying his tuning magic to the engine. Going down the crankcase induction route brought with it a whole new number of practical and clearance issues which needed addressing. Modifications to the clutch cable adjuster, positioning of the carb, now on the right, but much further back than a TS1, required a bit of work on the manifold and floorboard strut. Routing of the fuel pipe was unconventional too, involving the resiting of the fuel tap (via Oiltek). Chalkie made a one-off rubber mount for the carb. Even more careful trimming of material (4mm in one instance) from the engine casing, engine pivot and rear mudguard allowed everything to shoehorn into place while static. Under load, with a rider on board, the carburettor was still fouling. The crankcaseinduced Avanti, being a very limited edition set-up, does mean that advice, and sharing experiences with fellow owners, is equally limited. Luckily for Bruce, just 30 miles away from him, Adam Winstone has a similar Lambretta. Winding the adjustable Readspeed shock out by 12mm provided the solution. Having commissioned a CCI and Li240 badge for each side of the legshields and a gel-padded seat, by January 2020 Bruce's now-evolved dream Lambretta was ready for setting up, with different timing and exhaust combinations tried. Between lockdowns, Bruce managed to finish running his new engine in with a trip to Dartmoor in September. In December 2020, after fitting an Agusto Auto retard unit in November, it
was back to Chalkie at Replay for a re-dyno test and a few final tweaks. His dream scooter registered 23.5bhp. “After five years I have the scooter of my dreams, one that stays true to its classic design yet is quite different. Unique. It's a vast improvement on the original in terms of performance, reliability, handling and safety. She will cruise at 70mph for as long as you want but will accelerate and stop quickly when you want to have fun. To me, she is the most beautiful scooter in existence. I can honestly say, other than replacing the motorcycle master cylinder for a hidden one, there is nothing I can think of that I need or want to change. This is my scooter, there are many like it, but this one is mine.”
Words: Sarge Photographs: Gary Chapman