SCRAMBLER - VALVE CLEARANCE MEASUREMENT AND ADJUSTMENT
REMOVE THE SPARK PLUGS
Remove the spark plug boots (1) and the spark plugs (2) from the horizontal and vertical cylinders.
With the sparkplugs removed rotate the engine turning tool counter clockwise (from the left side of the engine) until the horizontal cylinder comes to the top if its stroke: Top Dead Center (TDC).
TDC occurs at the top of the compression stroke. You can feel air rushing out of the cylinder as the piston comes up on the compression stroke. The magnet, gently inserted into the cylinder, will give a visual indication when the piston has reached the top of the stroke. (The handle of the engine turning tool will be in line with the horizontal cylinder).
IMPORTANT: With the horizontal cylinder at TDC the engine is in the “HOME” position. The HOME position is the condition where all the timing marks will align (useful for belt changes).
The horizontal cylinder is also in the “rest” position, meaning there is no tension on the opening and closing rockers and shims. The “rest” position is the correct position to measure the valve clearances.
Verify the rest position by spinning the opening shim with your finger: there is no tension on the valves at this time and the measurements will be correct.
Slowly rotate the engine turning tool counter clockwise 270 degrees to bring the vertical cylinder to top dead center. When the vertical cylinder is on the compression stroke the air will rush out of the cylinder; a thumb or finger lightly covering the spark plug hole is a good way to feel the air rushing out. Using the magnet and slight adjustments with the engine turning tool, you will quickly locate the TDC of the vertical cylinder. Repeat the measurements for the opening and closing clearances and record those readings in the table above.
|Opening Shim Clearance|
|Intake||.10 - .15mm|
|Exhaust||.10 - .15mm|
|Closing Shim Clearance|
0 - .05mm
|Exhaust||0 - .05mm|
|Opening Shim Clearance|
|Intake||.10 - .15mm|
|Exhaust||10 - .15mm|
|Closing Shim Clearance|
|Intake||0 - .05mm|
|Exhaust||0 - .05mm|
Determine if the clearances are within specification by comparing the measurements you recorded to the Factory Specification. Any measurement that exceeds Factory Specifications will require a shim change to bring the clearance within Factory Specification.
First, subtract the lowest Factory Specification (.1 for intake, .0 for exhaust) from your measurement and record that number in the difference column. If your measurement is greater than the factory specification, record the difference in the "DIFFERENCE" column. This amount will be added to the shim measurement to determine replacement shim size.
Refer to the following sections for shim removal, measurement, and replacement. Remember to place the cylinder being worked on at TDC for ease of shim removal (no tension on the valve/shims)
OPENING SHIM REMOVAL, MEASUREMENT, REPLACEMENT
Note: be sure to segregate and mark all pieces/parts removed so there is no question on reassembly.
Once the clip is removed the opening rocker (5) will need to be slid out of the way to access the opening shim. This will take some wiggling/working
the cams back and forth to get the opening rocker to slide. If the cam belts are removed, wiggle the cam gear to get the rocker to slide off. If the cam
belts are still in place, use the engine turning tool to wiggle the shaft and release the opening rocker to slide to the side (arrow).
|ADD to||Existing Shim|
Second, measure the existing shim and add the number in the difference column to determine the size of the new shim to bring the clearances back into specification.
Put Opening shim onto valve stem then slide the opening rocker over the opening shim. REMEMBER, you will have to wiggle the cam (belts removed) or the motor using the Engine rotating too l(belts installed) to get the cams in position to slide the rocker over the valve.
Press down on the Closing rocker to expose the retaining rings. Slight engine rotation may be required to get the rocker to move far enough to expose the retaining rings. The retaining rings are in two halves.
Obtain the correct shim(s) and reassemble the valve train. Slide the closing shim onto the valve stem, The wider side slides onto the valve stem first.
Record the difference from Table 1 in the correct column in Table 2. Add this measurement to the existing shim size (that you measured): this will be the size of the new shim required to bring the clearances back into Factory Specification.
Note, it is not always possible to get the exact shim size, a larger shim can be made to the correct size using emery paper to adjust the size of the shim.
With the valve in the “rest” position, slide the feeler gauge between the opening rocker arm and the opening shim. Begin measuring using a thin gauge, ~ .05mm; proceed using thicker/thinner gauges until the gap can be determined. The correct feeling is one of slight resistance, similar to the feeling of inserting the gauge into a large book and moving it between the pages.
Measure the valve clearances for both the intake valve (middle of the “vee, ) and the exhaust side (where the exhaust exits the cylinder head)
Record measurements in the table below.
Once the plug is removed from the generator cover, install the engine turning tool. , making sure the tangs on the tool engage the indents on the crank shaft (4).
Tighten the retaining bolt snug with a 13 mm wrench.
The valve shim measuring tool and the electronic caliper will be used to take the measurement. The tool sets inside of the closing shim and gives a standard 10mm addition to your measurement.
Depress the closing rocker far enough to allow the groove in the valve stem to get exposed. Install the half rings (retaining rings). Do this with your finger or dip the end of the screwdriver in a little oil and use the screwdriver to install the half rings.
Open the micrometer sufficiently to allow the Opening Shim to fit between the jaws of the micrometer. The flat side of the Opening Shim should rest against the stationary jaw of the micrometer. The moveable portion of the micrometer will fit inside the recessed portion of the opening shim.
v Vertical Cylinder Vertical Cylinder Horizontal Cylinder.
The Desmodromic (Desmo) engines use a positive valve control system to open and close the valves at the same time in the combustion cycle regardless of RPM. The Desmo valve system use an opening rocker arm and a closing rocker arm that press on shims attached to the valve stem to open and close the valve in a precisely controlled manner: as the components wear, the gap (clearance) between the rocker and the shim changes. To compensate for these naturally occurring changes, the shims are replaced with thicker/thinner shims to bring the gap back into specification.
Ducati and Scrambler Tool Kits
Using a machinist’s scribe or another pointed tool, pry off the spring clip (4) from the rocker shaft.
WARNING, this clip will fly into your eye or to parts unknown
if it isn’t restrained.
The Scrambler engine is an updated version of Ducati’s classic SOHC V-twin. It is an air-and-oil cooled two-valve engine. The valve service intervals are more frequent with the air/oil cooled engines; therefore the Scrambler Valve Adjustment Intervals are 7500 miles. It is normal for the valve clearances to change over time shim surfaces against the rocker arms and the seating of the valves into the cylinder head. As the engine is run, the face of the valves and seats wear as they bed into each other (opener clearances get smaller and the closer clearances get bigger). The result is opening and closing clearances that change with use. Bringing the valve clearances into factory specifications assures the best possible performance of your scrambler.
Place a clamp on the valve. In addition to having the cylinder at TDC, this is a little extra insurance to keep the valve from dropping into the cylinder
CHECKING VALVE CLEARANCES
Prior to checking the clearances, some disassembly required. It is best to have as little fuel as possible in the gas tank before beginning this procedure. It is easiest to measure all the clearances prior to disassembling the valve train to replace the shims.
1. Place the motorcycle on a swing arm stand (optional), transmission in neutral.
2. Remove the seat.
3. Remove the fuel tank.
4. Remove the blow-by (part of the air box)
5. Remove the following components from the electrical component box:
b. Starter Relay
c. Fuse box
6. Remove the cylinder head valve covers (1) ,be careful if not replacing the gaskets with new ones.
Use the magnet or magnet end of a screwdriver to extract both halves of the (13) retaining rings and set aside in a very safe place (a zip lock bag properly labeled with the valve the rings belong to).
Turn the caliper on. Close the jaws using light pressure. Select the unit of measure: either inch or mm. The shims are designated by Ducati in millimeters and using mm as the unit of measure simplifies new shim size selection. Press ZERO to set the base line for the caliper.
3.Closing Rocker Arm
5.Opening Rocker Arm
With the retaining rings removed, you can now slide the closing shim up and off the valve stem. If the shim gets “stuck” at the top of the valve stem, it is an indication the valve stem has mushroomed a bit. Some emery cloth/sandpaper is needed to remove the wide part at the top of the valve stem to provide clearance for the shim to slide off.
Remove the Opening shim from the valve stem.
CLOSING SHIM REMOVAL AND MEASUREMENT
If the closing shim needs replacement, remove the opening shim as described in the previous section. The valve stem is exposed with the opening rocker slid to the side.
Once the rocker is in place, press the spring clip into place. Some firm pressure will be required.
Once the valve is reassembled, re-check the clearances to verify the valve train is within specification. With the cam belts installed, rotate the engine to verify smooth operation.
Reassemble as required.
Place the Shim Measuring Tool inside the closing shim (narrow end in) and measure the overall length.
REMEMBER- The TOOL adds 10mm to the measurement: subtract 10mm from the measurement and record your number
in table 2 (in the example pictured, 6.57 would be recorded in Table 2).
Use table 2 to determine the new closing shim size: measured shim size +/- the excessive clearance.
Closing Shim Clearance
Once the opening clearances have been measured, measure and record the closing clearances.
Slide a feeler gauge between the closing rocker arm and the closing shim to measure the clearance. Record your measurements in the table.
After the clearances for the horizontal cylinder have been measured proceed to taking measurements for the vertical cylinder.
Working from vehicle left-hand side, loosen the two screws (3) and remove plug (1) from generator cover (2).
While depressing the closing rocker, set a half ring in place on the valve stem. Rotate this ring around to the back side of the valve stem to leave room for the other half ring. Install the other half ring and slowly release the pressure from the closing rocker, making sure the half-rings seat onto the valve stem correctly.
DESMO Tool Rental
Ducati and Scrambler - D.I.Y - simplified
NOTE: The Opening Shim has a Flat side and a recessed side. Using light pressure, close the micrometer all the way and “zero” the unit: hold the On/Off/Set button until all Zeros appear in the display.