Vespa GTS tuning – 24bhp Malossi from PM Tuning | FEATURE

The Vespa GTS 250 was launched way back in 2005, quickly followed by the 300. Since then it’s pretty much replaced the Vespa PX as the long-distance scooter of choice for the progressive Vespa lover. It’s also found a place in the hearts of the criminal underbelly. Drug runners, mobile phone thieves, gang members and killers have all found a use for the regularly stolen 80mph ‘moped.’ Strangely though, even now tuning them hasn’t really caught on.

The reasons for that are that, in comparison to two-stroke tuning, it’s not quite as straightforward for the home mechanic. It’s also expensive and the gains are governed to a large degree by the rev limiter, you gain better acceleration but not necessarily higher top speeds. I’ve ridden a couple of Malossi V4 kitted scooters in the past and they were pretty impressive but at the time the rev limiter spoilt the party. Yes, they’d accelerate very well but you’d be bouncing off the limiter much too quickly and it annoyed me. Malossi gear kits helped out to some extent once they arrived. 

Aside from gear kits. there are lots more tuning parts available now and a greater understanding of four-stroke tuning by a few old-school scooter tuners. Lancashire based, PM Tuning, have been seeing just what they can do with the parts on a couple of brand new GTS 300s sent in by customers from down south. 

The need for speed

Although Piaggio quote a power output of 22bhp (measured at the crank), a standard GTS 300 is actually around 16-18 bhp at the rear wheel. It makes the power quite well though and will do a genuine 82mph on the road before reaching the limiter. Of course, fuel economy, tank range and the reliability of what is essentially a very useable standard scooter is all well and good but that’s not fast enough for some of us and the quest for power can often cloud the sensible side of our brain. That’s where the owner of this brand new GTS 300 found himself. Have a look at the video above as Paul Melici explains what’s been done to the engine. Not only that but it’s also had the brakes and suspension upgraded all the way around, turning it into quite a potent package.

PM Tuning work done to this engine

Dyno figures

Torque ain’t cheap but the tuning work and set up have increased the torque of this engine from a standard 12.99ft lbs @ 7005 rpm to 15.58 ft lbs @ 8039 rpm. Power has also increased from a standard 16 bhp @ 7474 rpm to 23.9 bhp @ 8237 rpm with a nice spread of power. 

On the road

Damp roads and near-freezing temperatures aren’t the perfect time to be trusted with a brand new scooter that’s just had a fair few quid spent on it and that the owner hasn’t even ridden yet but not to worry. 

Press the button and the scooter bursts into life, breathing angrily through the PM exhaust, give it some revs and unsurprisingly it sounds like it’s willing enough. With cold new tyres, I’m not taking too many chances once I’m out on the road but it’s still not long until I feel the ASR – Anti Slip Regulation cutting in. It was quite kind of Piaggio to fit the system ready for tuners to make the best use of the tech. In fact the GTS is so eager to be let off the leash that any harsh acceleration on the damp roads will have the engine management cutting power to the rear wheel, feeling like the scooter is trying to over fuel or die on me. Luckily you can also switch the ASR off. 

On straight line acceleration, this thing is good fun, it’s off like a rocket in comparison to a standard Vespa GTS 300. I find that kind of acceleration quite addictive. One thing that did surprise me is that the PM exhaust didn’t pop on the overrun like a GTS PM exhaust usually does. I asked Paul why, “We’ve used the PM fuel module and what we tend to do is set them up quite rich at the bottom end, which improves the torque curve and stops the downpipe from getting as hot. The popping is just unburnt fuel igniting prematurely in the downpipe which pops as you come off the throttle.” 

Limiting factors

Wind this thing up and it flies, ok it’s not actually much faster at the top end than a standard GTS but for fun away from the lights, or around your favourite local roads it’s excellent. One good thing is that thanks to the gear kit you aren’t constantly hitting the limiter, in fact even flat out I didn’t hit the limiter. Given a longer motorway journey I’m sure you can have it bouncing off the limit but in normal use, it makes the scooter nicer to ride than the previous V4 kitted GTS’ I’ve ridden. This scooter has also had Bitubo suspension fitted at both ends and PM Saw wavy discs, it certainly felt well planted and stopped well. 

New products always in development…