Ducati 900 ENGINES : NOT ALL CREATED EQUAL
Something many people do not know is that not all the 900 Ducati engines are the same. There are five different engine specs that I know off, being as follows :
- The best engine came in all 91 to 97 900 SS and SL bikes. These engines were also used in 900 Monster up to engine number 037727 ( late 1996 build ) and the 98/99 900 Monster Special.
- The not so good carb engine came in 900 Monster from engine number 037728 and the Cagiva Elefant series. The differences are camshafts and valves. These lower spec engines have 750 cams and valves. The valves are a couple of mm smaller. The cams are a little wacky, being about the same duration, but lower lift than the good 900 cams, with different timing, much wider lobe separation and less overlap. To my mind, they are an old cam design, borne out by the part number beginning with 0370, indicating something from the early or mid eighties. The inlet timing and lift is almost the same as the 4V Strada cam. Now that I think about it, the exhaust is similar to the 4V exhaust also.
As far as I am concerned, the only thing these cams are good for opening is the bin as you throw them away. Riding 900 Monsters with the detuned engine makes you wonder what the hell they thought they were going to achieve. It does explain, however, why the Elefants always felt slow for a 900.
3 engines in this series ( maybe 4, as the fuel injected Monster engine may have different gearbox ratios to the SS. The cams are the same though. ), with cams being the main difference.
- To get the wacky one out of the way first. The 900 ie Cagiva Elefant of 1990 had a fuel injected version of the 906 engine, but only a 5 speed gear box. At least the only one I have ever ridden did. Not worth worrying about too much. I don't even care what cams are in this one.
- The most powerful 900 2V in standard trim, the new SS / Monster engine has longer duration/higher lift cams than the carb SS engine. Apart from that and the efi, I believe they are basically the same. I could be wrong, but it's not important enough to me to go and make a detailed check. The cams are very similar to the ST2 cams, although the ST2 cams have a little more lobe separation, for a little less overlap.
- Obviously having a go at Cagiva for the past, the engines supplied for use in the Gran Canyons appear to be fuel injected versions of the old Elefant engine, with the crappy cams and small valves. They certainly feel that way. These engines do use the Weber Marelli 1.6M ecu though, as opposed to the 1.5M ecu used in the SS / Monster. On this point, you have to award the win to Cagiva. Digressing a little, I am fitting some 900 SS FI cams to a Gran Canyon in the near future so we will see what the change brings. Should be an absolute hoot, given the way our shop 900 SS FI goes. A dyno test has shown a std Cagiva Gran Canyon makes 65 Hp, about 13 down on the injected 900SS engine it shares everything, but the heads and cams with.
So there you have it. If you have a late model 900 Monster, the first mod to make is getting rid of the standard cams and maybe the valves. This puts you behind the eight ball from the start unfortunately. I have ridden one of these Monsters with a 944 kit and a jet kit and could not believe just how slow it was. It was only when I checked the build date that I realised what was wrong. It felt much the same as a standard early model, maybe even a little slower. Not what I would expect from a 944.
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