Ducati ST4

Hopped-up engines in standard chassis have always been a recipe for fun. More power equals more thrills, especially if the outward appearance gives no hint of the combustion fury burning within. Hot-rodders have known this for years, along with Renault and their crowd-pleasing F1-engined Espace. You’ll believe an MPV can fly after witnessing that particular corporate calling card.

But Ducati are making just such a Q-vehicle widely available, and it’s called the ST4. While outwardly identical to the ST2, which used the two-valve air-cooled engine from the old 907ie, the ST4 benefits from the four-valve water-cooled 916 unit. Cue instant 26bhp power gain and a grin wider than the Cheshire Cat’s.

But the swap wasn’t as straightforward as just shoehorning the sporting motor into the ST2’s sports touring frame. The 916’s cylinder heads needed to be completely redesigned in order to get the engine to fit and the slimmed-down unit was eventually 10mm narrower front to rear, as well as slightly shorter. The modifications were necessary to stop the front cylinder hitting the front wheel under braking, and also to make room for a decently sized airbox.

The newly sized engine could also be placed in the appropriate spot in the frame, keeping the 49/51% weight distribution. The only giveaways to the bike’s new character are a small ST4 sticker on the tail unit, while some grovelling on the ground and peering up the fairing reveals a water-jacketed cylinder poking between the radiator and the oil cooler. On the move the ST’s a complete street-sleeper.

The suspension is a carry-over from the ST2 (despite the additional plumbing the ST4 is only 1kg heavier than the earlier model) so a leap from 80bhp to 106bhp can unsettle it a bit. No matter, with a conservative 24°-head angle the ST can still be chucked over onto its footrests rapidly enough, and once cranked over it remains stable. Keep the engine between 6500 and 9000rpm and the sporting side takes over, but conversely the reprogrammed fuel injection allows the engine to lug away from as low as 2500rpm even two-up.

The second year of production saw an increase in the rear rim width for even sportier rubberwear, while the notoriously self-destructive sidestand of previous Ducatis was finally replaced by one that didn’t dump the whole plot on its fairing side at the earliest opportunity.

The engine swap endows the ST4 with wheelie-pulling stomp and a real turn of speed in the mid-range, but ride it sedately and everyone will think it’s the sensible ST2 tourer. Open the taps and surprise them…

Alternatives: Honda VFR800Fi; Aprilia SLV1000 Falco; Triumph Sprint ST

ENGINE AND CLUTCH

THE ST4 is proving itself by racking up huge mileages. But there are problems to be aware of though, thankfully, the list isn’t too long or varied. The biggest culprit, according to owners and trade members, is the clutch.

It has a habit of shedding its entire assembly since the retaining nut that holds the basket to the drive shaft can un-do.

The only cure is to make sure it’s done up really tight in the first place, and secured with Loctite, or similar. In fact, several Ducati dealers suggest that the torque setting should be " FTM " , which stands for " F***ing Tight Mate " !

Like the clutch, the generator can come loose if the bike has been ridden hard. This will show itself as a deep rumbling noise when the bike is on tickover. In most cases all that is required is a quick tighten-up.

SERVICE HISTORY

Make sure the bike has a full service history with a recognised Ducati dealer.

As a part of the servicing, the cam belts should be replaced every 16,000 miles. Be aware of this when looking and ask the owner the last time it was done. You may catch him out – it’s surprising how easy it is to do if you know the correct service intervals for all major parts. For instance, if he says the bike has done 10,000 miles but he also says the belts have been changed the odometer may well have been fiddled, or replaced with one with a lower reading. However, also accept that the belts should be changed at 36 months even if 16,000 miles haven’t been accumulated.

BRAKES AND SUSPENSION

Good from new, the brakes tend to lose their bite as the miles on the speedo increase. A new set of braided lines will help to bring the performance back to its former glory but check the pistons aren’t overly corroded or sticking. Rear suspension problems crop up from time to time. Straight from the crate, the ST4 is arguably a little under-sprung and under-damped, and that’s especially true if pillions are carried for any length of time.

After a few thousand miles have been racked up the damping and spring lose a little more of their ability to cope so check the shock before you buy by asking the owner to set the damping to its maximum then push down on the rear seat. Notice how quickly the seat returns to its normal position. Now repeat the procedure with the damping settings on their lowest settings. There should be a marked difference between the two. If not a new shock may be in order.

ACCESSORIES AND LUGGAGE

Though rare, there have been examples of the nylon fuel filter breaking down, allowing strands to get caught in the line causing fuel starvation. The ST4 is built to tour and cover long distances, so expect chains and sprockets to be nearing the end of their life. If they’re not, it’s a bonus. Also expect some bikes to sport aftermarket accessories. Ducati’s own luggage system is a popular addition and robust. But check it locks and closes properly.