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Monster S4


We are use to getting calls from all over the place for our services but it was still quite a shock to get a call from Geneva enquiring if we could service and set up a Monster S4 for mountain pass and city use. The call was from Ben Lark, based in that city.  His Monster S4 was used for the daily commute into the city and just wasn't coming up to snuff.

He had heard of our Full Monty 'make the standard parts work better approach' and fancied that we could make his daily ride a bunch more exciting.

The Monster S4 was unique in the Ducati range when it was launched, a water cooled Desmo Quattro with a Monster look, using an ST2/4/4S chassis and engine the look of the bike was modified into a Monster rather than the more staid look of the tourer.

Subsequent to the launch of this bike the rest of the monster range was updated with the same chassis being used throughout. Obviously these other Monsters use the aircooled engines (620/800/900/1000Due) but the basic chassis is the same. This is good news for us as the factory is issuing these bikes with various different setups; all of which can be modified just as we modified Bens.  Now the 996 S4R version is out we can play with that just as much.

Ben's complaint was that the bike was far from the lithe sports bike that he thought he was buying, the bike needed levering into corners and didn't respond to riding inputs, cornering or throttle

Now given that the chassis is the same as the ST4, on which we have done quite a few miles ourselves it didn't seem too difficult to change the setup on the chassis, and given that the engine is virtually identical that shouldn't be a problem either ...

Now I say virtually identical, the castings are the same, the crank, pistons and rods are the same, but the cams and gearbox are different.  The gearbox is the closer ratio '748' style box, my favourite in the range (have a look at the 748R/RS article if you want a bit more info on this). The box makes the bike more snappy, with smaller jumps between the top three ratios, just what you want when hooning around.

The cams are different too, well the inlet is any way, with 10 degrees less duration than the historic 916/996 Bip style and a reduced diameter down pipe (40mm, like the old 851/888 rather than the 45mm of the 916 and ST4).

The fuel injection system was one of the first applications that used the new 5.9 computer, used to save space (all electronics have to go under the fuel tank) it doesn't have the easily replaceable Eprom that features on the older bikes with the 1.6 and P8 computers. 

Now you might think that all these mods would really make life difficult; would we need new pipes and cams? Well no we didn't need to 'cos Ben didn't want to wake up the locals on the way to work so the standard mufflers were to stay on and he wanted a healthy midrange as well as some more throttle response. The problem was that bigger pipes and hotter cams would lose midrange and response.

We decided that we could do a lot with the standard engine internals by giving the bike a Full Monty, using our special chassis jig to set up the chassis and playing with the standard computer and airbox to get the best torque curve we could.

Options did include using the new FIM replacement computer for the 5.9 Marelli; cost ruled it out this time but there is certainly more performance to come from that area and will be fitted at the bikes next service (yes, its coming back from Geneva for its next service too!!).

You can see the change in fueling on the bottom line of the dyno graphs below; we used the idle mixture adjuster inside the computer (using FIM's Ultimap software) to richen up what should in theory be the idle mixture but as you can see the effect is felt right through the range.  There is something clearly different in the way this software works as this really shouldn't happen.

To explain; the typical fuel pulse at tickover on a single injector engine, say a 916 is around 2.3 m/sec at 1000 rpm and 1.1 degrees of throttle. The manual trimmer on a P8 or 1.6 computer will extend that pulse time plus or minus 0.24m/secso the variation is over 10%; by the time you get to the 11 m/sec pulses up at 10,000 rpm the variation is just over 2%.  Looking at the effect the trimmer in the 5.9 there seems to be a greater change further up the system. Possibly as much as 5 or 6 %.

So if the 5.9 computer will allow this much change why do we like the FIM replacement version so much? The main problem is that the trimmer variations are the inverse of the engines actual requirements, and are a 'one shot' change, and on this bike remember we kept the original 'quiet' mufflers so there wasn't much of a change required.

The latest Ducati engines also have some fairly restrictive rev limits, especially this S4, with the rev limiter coming in at 9500 rpm, that's pretty low when you consider that the virtually identical ST4 touring engine and 916 Biposto is redlined at 10400 RPM. These are not gratuitous racing redlines, they are perfectly normal, all the parts that keep the motor together even have the same part numbers! This makes our ability to set the FIM Ultimap computers redline wherever we want an even bigger benefit.

Our philosophy has always been to get the best out of accurately arranging the standard components, and then fitting a fuel map to suit. We cannot change the one inside a standard 5.9 computer, but we do value the ability to fit a map that has the correct secondary 'correction' map (have a look at the Weber Fuel injection article for a more detailed report on this).  The ability to set the secondary map correctly and to then also tailor the main fuel map, rev limiter and ignition curve will give advantages a clear leap above the trimmer mod. We regularly change one small area of a map to suit a particular rider or engine setting. 

For this bike the budget stopped at the trimmer mod but Ben has already decided that next year will see the FIM Ultimap computer on the bike.

So, to summarize, what did we do?

We did a Full Monty service (ie a replacement for a 6000 mile or 12000 mile service, plus a semi Blueprint of the engine) including lapping the valves to their seats to improve their sealing; setting the valve clearances to the original settings; re setting the piston to cylinder head clearance to those used on our race engines and, then setting the cams to the most accurate settings we can get (on this engine the numbers we wanted were the ones the engine was supposed to come with, we can do other settings for different shape power bands if wanted, (like our Grunter settings for 748SPS and 996Bips).

We also adjusted the fueling for the airbox mods; the original mufflers remained on the bike though. We then set the chassis for a much quicker turning bike with a raised centre of gravity. On this particular bike we fitted an Ohlins shock but you can reset the chassis just as well with the standard one, you don't get the plush Ohlins ride then though.

Finally we fitted a new top triple clamp and some really cool Gold anodised Renthal Superbike bars.

Have a look at the dyno charts, just revel in the big chunk of midrange torque (and feel free to compare it to the ST4 and 996 Biposto charts else where on this site, this bike may not have the last few top end horsepower but the combination of a good build, short duration cams and the small header pipes really gets things moving in the midrange.

With a close ratio box, reduced overall gearing and a significantly quicker turning chassis this thing rocks.

This is what Ben said after he had had the bike for a couple of months

"When I bought the S4, I was expecting a cross between a super motard and a serious sportsbike wrapped in a coating of Italian V twin magic. What better than the famous Monster, bred together with a 916 engine tuned for midrange? Although the bike was certainly not a complete disappointment, there was something about it that was somehow lacking. It handled okay and went okay, but you expect more than that from a Ducati maybe I had made a mistake ... Enter Neil Spalding ...

I took the bike to Neil and we discussed what I was looking for. The bike tended to understeer, taking quite a bit of effort to hold down in corners, added to that, the rear tended to feel vague coming out of corners that were anything but completely smooth. Low down power and midrange tracatability were also disappointing given the fact that this was a legendary motor that had been retuned for naked, fairly upright riding where top speed was not the issue.  To cap it all, the forged handlebars dictated an uncomfortable and un-natural riding position and did not suit that classic Monster look. Given that all my riding is either in the city or mountains, which is why I opted for this particular bike, I was a mite disappointed!

I don't know what he did, but handling is now razor sharp, it turns quickly, tracks beautifully and at the same time is rock solid. The engine pulls like the flying scotsman in all gears and pick up off the line is impressive. The riding position has been vastly improved with the addition of an S4R steering head and yoke, combined with a set of Renthal superbike bars. At the same time the standard pipes have been retained, but some of that Ducati growl has been liberated by airbox mods that at the same time liberate more power.

As Neil said when I picked it up ... you are going to have to relearn how to ride it ... how right he was! I live in the French Alps and the 9 hour ride home from Kent gave me a taste of what is waiting to be discovered ... autoroute, nationale and mountain road were all despatched in a memorable ride that flew by ... roll on the daily race, I mean commute to work!"

If I get any more eulogies like that we are going to have to fit bigger doors to the workshop !

Neil Spalding 2003

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