Pound for pound four stroke tuning is less rewarding than two-stroke tuning. For less than a grand you can bolt a decent kit, exhaust and carb on to a Vespa PX and increase its power by 40% or more. Sadly, power gains aren’t quite so cheap or easy to come by on a modern fuel-injected four stroke.
A few months ago, we featured a 24bhp PM Tuning tuned, Malossi V4 kitted GTS. That particular scooter gained 49.375% power taking it from a standard 16bhp to 23.9bhp. A decent gain, but the parts alone are double the cost of tuning your PX. PM Tuning wanted to take things up a notch though and had another customer with money burning holes in his pockets.
Pushing the boundaries
This customer, Adrian Maelzer sent a brand-new Vespa Sei Giorni up to PM and asked for a full spec tune, he wanted them to push the boundaries a bit and PM were happy to oblige.
Not only did he want the most powerful GTS/GTV they’d produced but he also wanted the scooter to look more retro than a standard GTV. It also had to have the best brakes and suspension. Paul Melici and the crew at PM were happy to oblige and the Seventh Day GTV was born.
Whilst the engine was out of the frame they set about removing the bulky rear light unit, this leaves a gaping hole in the bodywork, so they plated the hole from the inside and filled it with as little filler as possible to avoid cracking later. The standard matt paint isn’t easy to match but the rear end was resprayed and you wouldn’t know the difference. A smaller retro rear light fits neatly below the stylish custom rear carrier and looks much more in keeping with the GTVs styling, something Piaggio should have done at the factory. A six-digit black reg plate finishes things off nicely.
PM have an eye for detail and de-chromed the whole scooter. Black replaces chrome on the headlight, replaces silver on the transmission cover, the handlebars, bar end mirrors, and legshield trim. A modified carbon PM Tuning Runner screen also replaces the standard GTV screen (incidentally we’re in the process of developing a new SLUK screen for the GTV so watch this space).
A PM carbon fork cover, knee pad covers and rolling nut cover also finish the styling off nicely. The seat was also recovered in a vintage dual tan brown with contra stitching. Finally, smoked indicators finish things off perfectly.
Front end mods
This scooter was set to increase in power significantly, so the suspension was upgraded both front and rear by adding adjustable Bitubo shocks. Brembo brakes were also used at both ends, a hefty 4-pot front and 34mm dual piston rear. It’s not a straightforward bolt-on job though, PM think it’s the first conversion of this type on a Euro 4 spec ABS GTS. It involved machining the front wheel sensor, making extended CNC machined caliper extension brackets, machining the outer brake pad and offsetting the front wheel.
The banjo bolt for the front brake hose runs too close to the front rim to be able to mount it any other way. The rear wheel was swapped for a 13” Gilera Runner ST wheel to gain the extra clearance required for the caliper, the ABS rotor also had to be machined back on to the rim for it to read correctly. Finally, PM Tuning Saw discs replaced the standard items. Lots of work.
Make some noise
The scooter barks through a baffle-less PM68 exhaust and induction roar is heightened thanks to the foam air filter. It’s certainly not the kind of scooter you can sneak about on, it’s loud but the fueling is bang on, with no popping on the overrun. The engine was still fresh, with only setting up time on the dyno and a few road miles since the rebuild.
I was allowed to ride it but couldn’t afford to break it. That’s one advantage of a liquid-cooled four stroke engine though, they are harder to break.
Traffic light racing
The owner lives in London and runs a standard GTS around town (although that is also in at PM for some tuning work). He wanted this GTV for his Sunday best machine, something like this will attract unwanted attention in the middle of the city, from both sides of the law. Even so, he also wants this scooter to be able to win the traffic light grand prix.
On the road
It was quite trusting of Adrian (and PM) to allow me to take the newly finished scooter out for a spin. Especially seeing as the owner hadn’t even seen it, let alone ridden it yet and was due to pick it up the following day…
Before starting the scooter I was advised to run it with the ASR turned off, the previous PM tuned GTS I’d ridden also needed to have its Anti Slip Regulation turned off to make it rideable. This one has a fair bit more power under the bonnet. The procedure is simple though, start the scooter and repress the starter button to switch the ASR off (on an ordinary GTS you press the separate ASR button.
I’d say he’ll have no problems beating most things away from the lights. From a standing start, it’s rapid. It gets away from the line quicker than a TMAX, despite having only half the Yamaha’s power.
It’ll quickly get up to 80mph and still not run out of steam (as you’ll see from the dyno in part 2). You can overtake at will, with enough power in the mid-range to give you the edge. Like the previous GTS, I rode at PM, this one didn’t hit the rev limiter. It’s been moved higher than standard by the Malossi gear up kit. Without being able to do a long trip, or rally on it I’m not sure if you’ll ever hit it on the road. Which is a good thing, nobody likes a rev limiter coming in to spoil the fun. Although of course, it is there for a reason.
As expected, the scooter can’t be ridden with the ASR left on, try and pull away quickly and it just cuts the power, far too intrusive and to be fair – if you’re spending this kind of money to go a bit quicker you don’t want electronic aids dictating how much fun you can have. With it turned off you can whack the throttle open and make full use of the power on tap. The GTV is also fairly easy to wheelie off the throttle, not that I’m particularly gifted in the stunting department.
The front-end modifications were done to allow the top spec Brembo brakes to be fitted (and of course the Bitubo shock) really have transformed things, the front brake is powerful and precise with plenty of feel at the lever. It’s not at all ‘grabby’ it just works. In fact, the whole front end works very well – probably the best GTS front brake and suspension I’ve used. The rear suspension is also very good, although the rear brake needed a bit more bedding in before you’ll get the best out of it.
The owner didn’t want to discuss how much this job had cost him but I’m sure you can all do the maths and realise that he could probably have bought another new GTS instead. That’s not really the point though. If you’re into scooters you’re into scooters. He could have bought a new 200bhp superbike, or sunk the money into a fast car but like you and me he’s into scooters. If you want to discuss the finer details and would like a fast GTS give PM Tuning a call.
Why be sensible?
Making unsuitable machines do unthinkable things isn’t sensible, it isn’t cheap and it isn’t what somebody of rational mind would ordinarily do but it sure is good fun and long may it continue.
In part 2 next week Paul Melici will be showing us how he got to 27bhp and we’ll have some on-board footage.
Words and photos: Iggy
The owner’s first impressions
Just a line to say thanks very much for delivering exactly what I was trying to achieve, Piaggio’s modern take on the 1950s 6 day race Vespa.
Upon getting the bike home and riding on familiar roads, after a few hundred miles I can now fully appreciate just what we have all created.
On low throttle, she rides with as much torque and precision as a fully able, stock 300 and when called upon it’s truly a beast that has shocked a few superbikes away from the lights and coming out of roundabouts.
I’m now used to the saddle and will certainly keep it as is and the finish on the rest of the bike is stunning, drawing admiring onlookers when parked – even my wife likes it.
Well done PM Tuning it was a pleasure working with you and thanks again…
Owners name: Adrian
Scooter name: Seventh Day GTV
Model: Vespa GTV Sei Giorni
Engine details: Malossi V4 cylinder kit and V4 head, Zirri camshaft, 38mm CNC inlet, ECU and throttle body, 350cc injector, PM variator kit, Dr Pulley Hit clutch, PM induction velocity stack, PM 68 exhaust
Top speed: Not yet run in
Power output: 27.3bhp (on a tight engine)
One-off parts: Modified CNC brake caliper extension, Brembo brake conversion, rear end modifications
Built and tuned by: PM Tuning
SLUK Shop – you can rely on us for quality parts and great service!