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900SS CARB WITH SOME VEE TWO CAMS

This report is one put together from a job we did quite a few (more than a few, actually) years ago. I’d been working at Moto Italiano, as we were then, for about a year. Back before I had a good (well, any) idea of what worked on these bikes, this probably put me in a similar place to that which many owners find themselves in when trying to decide what mods to make to their own bikes. It was the first bike I had to check and reset cam timing on too, so represented quite a big learning episode for me. Looking back, it just annoys me a little that we didn’t do all the things then that I would now. Which is the benefit of hindsight and experience. At least we’ve learnt something in the intervening years.

So, this ’95 900SS came in for some mufflers, in this case the local Omrae, and some Vee Two cams. Dynobike did the tuning after completion, back when they were in the little shop in Huntingdale. We did start out with some before runs, which is always good.

The Vee Two cams fitted were p.n. V2-03-210, the ones referred to as "torque" cams from memory. The same grind is also available from Ducati Performance, under the p.n. 964034AAA, or the old 06090. The table below compares them to std cams.

As you can see, the Vee Two cams have a much earlier closing of the inlet and exhaust valves, less overall duration and quite a bit more valve lift. The inlet centreline is also advanced 8 degrees. In the long manifold, carb model engines, they work rather well. There are a couple of dramas with fitting these cams however. The main one is that Vee Two stipulate the valve cutouts in the pistons need to be machined a little larger and a little deeper. This unfortunately means disassembly – removing the heads, a somewhat involved job on an SS (it’s easier to pull the engine out and do it on the bench) - is required. I have checked valve lift versus available piston – valve clearance for these engines, and this machining is required. I was hoping it could be avoided, but unfortunately not.

The other is that either the inlet valves need to be extended, or larger than std opening shims are needed. This was also spoken about in the 600M cam swap report, and is due once again to the smaller base circle required for the cam to accommodate the increased maximum lift. Given the heads are off for the piston work anyway, removing the valves and having them extended by welding is a pretty easy job for an experience head shop. The other option is the bigger shims, which can be sourced from Vee Two.

The graphs below show the results. The first graph is power, the second torque.

The green line is all std. As you can see, there is a big dip between 4,000 and 6,000 RPM. The torque curve really shows this up, and is due to the std mufflers. I have alluded to this in the 851 reports, as all the 851 models came with the same mufflers std, but the effect is much more pronounced on the 900 2V engines.

The blue line is with the Omrae mufflers fitted. Pretty much the std result, wouldn’t matter if they were Termignoni or Silomotor or Staintune, really. No surprises there.

The red line is with the Vee Two cams fitted. I believe the jetting was changed to make it a little richer, but really cannot remember. I can remember, however, that the increase in torque was up to 20% over std, and that the owner was very happy. Given he lived up in the hills, it was just what he was after. You can see that once the torque curve does start to fall, it drops away quicker than with the std cams, and is all over by 8,000 RPM. Given the nature of these long manifold engines, however, this is just about spot on.

Now, given I didn’t tune this engine, and that I wouldn’t have known what I was doing back then anyway, I’m not sure of what jetting changes were made. I know it had the std airbox lid. These days, I would run it with a Factory Pro jet kit and open airbox, which would help the curve all over and probably slow the torque drop off at the top end. This would really finish off the package, maximising what ( in my opinion, not that I’m biased, of course ) is a really great road bike engine. It was pretty cool to ride anyway, if my somewhat dodgy memory serves me correctly.

The final graph below includes another 900SS ( green ), this time a ‘97 model with Termis, std jetting and the std cams dialed. The red and blue lines are the same as the previous graphs. So, dialing the std cams has much less effect on the dyno power output than the Vee Two cams. This bike was pretty quick and responsive in its own right, with a very happy owner.