Ducati 600 MONSTER WITH SOME DIFFERENT CAMS

Next up for the hunnybunny mobile was some 900 cams. We have had some second handies sitting on a shelf for years that I’ve been looking for a bike to put them into, so this was a great opportunity. Fitting them is not a totally straightforward job though, as the extra lift of the 900 cams dictates they have a smaller base circle diameter on the opening lobes. This is due to the physical constraints of the head casting and the available room inside for movement. Not that accommodating this is a real issue, we just need to run some much larger than std opening shims. The best way to do it is to fit some longer valves, but pulling the heads is not something I do for fun ( I don’t have the time, and an ever greater lack of motivation for stuff like that ). So the bigger opening shims is a dead easy solution.

In the past I’ve sourced these from VEE TWO, but, in this case, I used std ones. Surprisingly, I got by with shims under 5.00mm, which is the largest available from Ducati. VEE TWO carry a complete range, in 0.05 increments, from the factory maximum of 5.00mm up to 7.50mm ( they also have the smaller ones too ). Which means I didn’t have to wait a day to finish the job, not that there was any real rush.

The 900 cams turned out to be not quite what I was expecting. The specs have always been given as 20/60 for the inlet timing, but I have found out since ( after I first did this cam swap and report ) that they are 24/70. This also means the std centreline is retarded 3 degrees from what I thought. I had suspected the specs I had were wrong, from my measurements when setting the timing on this bike, and from a cam doctor graph comparing the 600 and 900 cams that Doug Lofgren sent me. The table in the previous report has been updated to the correct specs now, and is also shown below. The 900 cams have more duration and more lift than the 600/750. Interestingly, Doug’s graph showed that both cams open the exhaust and shut the inlet over the same duration, with the 900 opening the inlet earlier and closing the exhaust later in a comparative sense, giving more overlap.

The 900 cam does have a bit more lift @ TDC which effects the cam settings I chose, but that’s the way it is. The lift @ TDC for the 900 cam fitted at what I thought was the std spec of 110 degree inlet centreline was the maximum I could have used anyway, and is the same as that from the previous cam dialing exercise. It gives an inlet closing figure ( the most important of all the four cam events ) 2 degrees retarded as compared to this bike when it was std. Originally, both cams in this bike were advanced 5 degrees from the std spec, at 114 degree centreline. Why, I have no idea, but that’s how it was. Usually, the cams in both 2V and 4V models come on the retarded side.

Below I have included the cam comparison table from the previous 600M report, for current reference.

The graphs below show the result. The first is for std mufflers. All std is green, 900 cams fitted and dialed is red, std cams dialed is blue.

The second graph is with Megacycle mufflers fitted. Std cams is green, 900 cams fitted and dialed in is red, std cams dialed is blue.

As is plainly obvious, a total waste of time. Adding insult to injury is the fact that I now have to refit the std cams, a mind numbingly tedious job at best. Think it’s tanty time ( not that anyone’s going to listen ). I was going to try a jet kit, but I’m all 600M’d out for the moment. Which means hunnybunny will be getting Minnie ( so named after the Minnie Mouse key ring used for identifying the key ) back as a cam dialed stocky.

So, after this extensive foray into the 600 engine, I am left with some insurmountable facts.

1. Any slip on mufflers will help performance in every way
2. Playing with the std cam timing will help, but it’s not a night and day change by any stretch of the imagination
3. Fitting the 900 cams is a waste of time
4. You can spend your money on big bore kits or longer cranks or big valves if you really need to make your 600 faster, or
5. Perhaps swap in a 750 or preferably 900 engine
6. But whichever way it’s a lot of money to spend on a 600, and modified bikes never resell well or for more
7. It is only a 600 after all
8. It’s quite good fun to ride the way it is, really

Time to go play with something else. Where’s that 888....

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