Ducati Scrambler User manual

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Scrambler

Valve Measurement and Adjustment User Guide

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Contents

Introduction ..............................................................................................................................3

Operation .................................................................................................................................3

Checking Valve Clearances .................................................................................................4

Remove the Spark Plugs.........................................................................................................4

Opening Shim Clearance Measurement………………………………………………………6

Closing Shim Clearance Measurement………………………………………………...………6

Determine if valves are within specification........................................................................7

Opening Shim Removal, Measurement, Replacement.....................................................7

Measure ................................................................................................................................8

Record...................................................................................................................................8

Closing Shim Removal and Measurement...........................................................................8

Measure ................................................................................................................................9

Reassembly.........................................................................................................................10

Appendix 1 –Ducati Scrambler Valve Measurement Recording Sheet.......................11

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Introduction

The Scrambler engine is an updated version of

Ducati’s classic SOHC V-twin. It is an air-and-oil

cooled two-valve engine displacing 803cc. The

valve service intervals are more frequent with the

air/oil cooled engines; therefore the Scrambler

Valve Adjustment Intervals are 7500 miles.

The shims don’t wear as much as the valve seats

do. 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 from your scrambler.

Operation

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 uses 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.

1. Valve

2. Closing Shim

3. Closing Rocker Arm

4. Retaining Clip

5. Opening Rocker Arm

6. Opening Shim

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Checking Valve Clearances

Before the clearances can be checked there is some disassembly required. Try and

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, 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:

a. Battery

b. Starter Relay

c. Fuse box

6. Remove the cylinder head valve covers (1) ,be careful if not replacing the

gaskets with new ones

Vertical Cylinder Vertical Cylinder Horizontal Cylinder

Remove the Spark Plugs

Remove the spark plug boots (1) and the spark plugs (2) from the horizontal and

vertical cylinders.

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Working from vehicle left-hand side, loosen the two

screws (3) and remove plug (1) from generator

cover (2)

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.

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 of the timing marks will align (useful for

belt changes).

The horizontal cylinder is also in the “rest” position (no tension on the valves). The

“rest” position is the correct position to measure the valve clearances. Verify the rest

position by spinning the opening shim with your finger.

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OPENING SHIM CLEARANCE MEASUREMENT

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 APPENDIX 1.

CLOSING SHIM CLEARANCE MEASUREMENT

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

APPENDIX 1.

The clearances for the horizontal

cylinder have been measured.

Repeat the measurements for the vertical cylinder:

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 APPENDIX 1.

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Determine if valves are within specification.

Determine if the clearances are within specification by comparing the

measurements you recorded to the Factory Specification. Any measurement that

exceeds Factory Specified Clearance will require changing a shim to bring the

clearance back into Factory Specification. The basic sequence is:

1. Look at the values you measured and recorded in (Column A) APPENDIX 1.

Note which measured clearances exceed the Factory Specified Clearance

(Column B).

2. Subtract the lowest Factory Specification (.1 for intake, .0 for exhaust) from

your measurement and record that number in Column C.

3. Measure the existing shim and record this number in Column D.

4. Add Columns C and D in order to determine the size of the new shim to bring

the clearances back into 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 or 400 grit wet/dry sandpaper to adjust the size of the shim.

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).

Refer to Appendix 1.

Opening Shim Removal, Measurement, Replacement

If either the opening

or the closing shims

require replacement

to bring the gap(s)

into specification

follow this procedure.

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.

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).

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Remove the Opening shim (6) from the valve stem.

Measure

NOTE: The Opening Shim has a Flat side and a recessed side. Using light pressure,

close the dial caliper all the way and “zero” the unit: hold the On/Off/Set button

until all Zeros appear in the display.

Open the Caliper 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.

Record

Record the measurements in Appendix 1.

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.

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.

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.

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Use the magnet or magnet end of the screwdriver to extract

both halves of the retaining rings and set aside in a very safe

place (a zip lock bag properly labelled with the valve the

rings belong to).

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.

Measure

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.

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.

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 Appendix 1.

In this example, the closing shim size would be 6.57mm.

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Reassembly

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.

Depress the closing rocker and 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.

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 sit onto the valve stem correctly.

Put Opening shim onto valve stem

Once installed, 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 tool(belts

installed) to get the cams in

position to slide the rocker

over the valve.

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.

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