I have written up detailed instructions that can be downloaded from Higgy's excellent web site here;
or look in the 750 magazine section
Over the last few days I've been checking the cam timing on my 906.
After triple checking my measurements this is what I came up with.Horizontal Cylinder
Inlet: Open 24 deg BTDC
Close 68 deg ABDC
Exhaust: Open 59 deg BBDC
Close 32 deg ATDC
Lobe Center Angle: 112 deg Vertical Cylinder
Inlet: Open 19 deg BTDC
Close 71.5 deg ABDC
Exhaust: Open 58 deg BBDC
Close 33 deg ATDC
Lobe Center Angle: 116 deg
The following is a work in progress,I welcome any input,pm me please.
I’m not a tuning guru by any standard, this is my first experience with cam timing and my knowledge is presently limited to working on my own 906 Paso so I’m going to concentrate on the procedure rather than the technical side. There are plenty of internet articles that cover the effects of advancing or retarding the cam timing. The Ducati factory specification for the 906 recommends a Lobe Centre Angle of 10 degrees. After discussing my findings with Brad at The bikeboy.org he recommended I advance my timing to 106 degrees on both cams. So far, what I have discovered is that by advancing the timing by 4 degrees increases the bottom end and mid-range power/torque but sacrifices some top end. My plan is to try some different settings so that I can get an idea myself what effect they have on performance. As for carrying out the job, it is not very difficult, just time consuming. There is no point in rushing it anyway, because the consequence of getting it wrong can be very costly. It took a couple of days to make up the tools and another day of setting up and taking and double checking measurements. Then there was the three days wait for the keys to arrive and....well you get the point.
Before I could do any measuring I made up some tools i.e.degree wheel, pointer, mount for dial indicator, piston stop, extension for dial.Alternatively you can buy them from parts suppliers.
The first step is to set the degree wheel to zero.
1. Remove both spark plugs.
2. Mount the degree wheel on the alternator end of the crank.
3. Mount the pointer.
4. Rotate the engine forward(anti-clockwise) and bring piston to the start of the compression
stroke.Do this by holding a finger on the plug hole and feeling for the pressure when the
piston starts to come up.
5. Screw in the piston stop and very,very gently
rotate the engine until the piston
rests against the stop.BE VERY,VERY GENTLE WHEN ROTATING THE ENGINE WITH THE
PISTON STOP IN AS YOU DON'T WANT TO PUT THE STOP THROUGH THE TOP OF THE
PISTON.ALSO, DO NOT ROTATE THE CRANK A FULL 360 DEGREES WITH THE STOP IN AS
THERE IS A CHANCE THAT THE VALVES MAY MAKE CONTACT WITH THE STOP
6. Loosen the degree wheel and set it to 0 deg TDC,without moving the crank
7. Unscrew the stop and rotate the crank past TDC just enough to allow the stop to be
screwed back in.(My stop takes up 38 degrees of rotation so I rotate the crank about
50 degrees).Screw the stop back in and rotate the crank very,very gently
reverse(clockwise) until the piston rests against the stop again.
8. Take note of the angle on the degree wheel.As mentioned earlier mine is 38 degrees.
9. Now loosen the degree wheel and set it to half of the angle noted in step 8.eg.If the angle
noted was 38 degrees then you would set the degree wheel to 19 deg,again without
moving the crank.
10. Unscrew the stop again and rotate the crank forward just enough to allow the stop to be
screwed back in, rotate the crank back gently
until the piston touches the stop
again.Repeat until the degree wheel reads the same either side of 0.The wheel is now set
The next step is to set up the dial indicator.
1. Remove the valve cover and screw the dial mount in it's place.
The plunger on the dial should be almost all the way in when the valve is closed.
Ensure the piston is at TDC.
2. Set the indicator to zero.
3. Insert a feeler gauge to take up the valve clearance,mine was .01mm(.004").
Taking the measurements.
All measurements should be taken while rotating the engine forward only. If you happen to go past your mark and rotate the engine back you will get an incorrect reading due to gear lash. I found a difference of around 2 degrees when I measured mine. Also, it is a good idea to measure everything at least 3-4 times to make sure you get the same result, plus it makes for good practice.
1. Rotate the crank until the indicator reads 1mm.Take note of the angle on the degree
wheel,mine was 19 degrees BTDC.
2. Continue to rotate the crank until the indicator reads 1mm before the valve closes.Take note
of the angle on the degree wheel,mine was 71.5 degrees ABDC.
Now for some maths.The formula for working out the lobe center angle is thus:
1. Inlet opening (IO) + inlet closing (IC) + 180 = duration
2. Duration / 2 = half duration
3. Half duration – IO = Lobe Center Angle
So in my case for the vertical inlet:
1. 19 + 71.5 + 180 = 270.5
2. 270.5 / 2 = 135
3. 135 - 19 = 116
I went through the process of measuring all the lobes just for my own reference but because the inlet and exhaust lobes are part of the same cam on a 2 valve motor it is only necessary to measure the inlet lobes to check if the timing needs to be adjusted.