Content .. 5 6 7 8 ..

BMW AG Motorcycle (R 850 C, R 1200 C). Manual - part 7

11.22

Removing valve gear holder

•

Remove camshaft sprocket cover.

•

Unscrew/press off camshaft sprocket.

Note:

If the camshaft sprocket (1) is not removed after
loosening, it must be held firmly and prevented from
falling into the engine block (e.g. with a cable strap).

•

Remove valve gear holder.

•

Secure rockers with a rubber band (2).

Note:

If no work is carried out on the valve gear holder, re-
move it together with the cylinder head.

RS110070

M6 x 60

M6 x 30

RS110051

11.23

Dismantling/reassembling valve gear
holder

•

Remove bearing cap.

•

Insert a suitable drift into the bore (arrow) of the
rocker shaft, and pull the shaft out of the mount
by twisting it in both directions.

•

Remove pushrods.

Caution:

Do not accidentally confuse rocker shafts and push-
rods.

RS110080

M8 x

11.24

•

Remove camshaft bearing cap (1).

•

Remove camshaft and bearings (2).

•

Remove bucket-type tappets.

Caution:

Do not accidentally confuse the bucket-type tap-
pets.

•

Reassemble in the reverse order of work.

Caution:

Note direction of installation (3) for camshaft bearing
cap. The cutout on the rocker shafts must be
aligned with the retaining holes.

Note:

Locate pushrods in ball cups on rockers and hold
the rockers together with a rubber band to secure
the pushrods in position.

Tightening torque:

M 8 screw, rocker shaft bearing cap ............ 15 Nm
M 8 screw for camshaft bearing cap ........... 15 Nm

•

Reposition the bearings until minimum endplay is
obtained.

End float of rocker:
min............................................ 0.05 mm (0.002 in)
max. ......................................... 0.40 mm (0.016 in)

RS110090

M8 x

RS110100

11.25

Removing cylinder head

RS110110

M6 x 30

M10 x 70

11.26

Dismantling, checking, repairing and
re-assembling cylinder head

Removing and installing valves

Caution:

Do not scratch sealing face on cylinder head. Place
the head on a clean, scratch-free surface.

•

Attach valve spring tensioner,
BMW No. 11 5 690, to cylinder head.

•

Clamp the valve springs.

•

Separate valve collet from spring plate by striking
the valve head gently.

•

Remove valve collet sections.

•

Relieve tension on valve springs.

•

Remove top/bottom spring plates, valve springs
and valves.

Removing valve stem seals

•

Pull off valve stem seal with pliers,
BMW No. 11 1 250.

Note:

If a valve is removed, the valve stem seal must be re-
newed.

RS110130

11 5 690

11 1 250

11.27

Checking valves for wear

•

Clean combustion residue from valves.

•

Check valve dimensions.

............................................See Technical data

Remachining valve seat

Caution:

Width (B) and diameter (D) must always be main-
tained when remachining the valve seat.

............................................See Technical data

Checking and repairing cylinder head

•

Remove combustion residues from combusion
chamber.

•

Check sealing face for damage/distortion, and
skim flat if necessary.

Skimming sealing
face: ........... max. 0.2 mm (0.008 in) metal removal

Checking valve guide for wear

•

Check valve guide bore.

............................................See Technical data

RS110890

11.28

Replacing valve guides

•

Heat cylinder head slowly and uniformly to
200 °C (392 °F) in a suitable oven.

Caution:

Wear protective gloves when handling heated parts.

•

Drive out valve guides with 5 mm (0.20 in) dia. ex-
tractor pin, BMW No. 11 5 674, from the com-
bustion chamber side.

•

Allow cylinder head to cool down to room tem-
perature (app. 20 °C/68 °F).

•

Examine valve guide bore for:

–

wear,

–

widening taper and

–

correct dimensions in H7 tolerance range
(12.500...12.518 mm/0.4921...0.4928 in).

Note:

Valve guides are installed in the cylinder head with
an interference fit of 0.015...0.044 mm
(0.0006...0.0017 in).

If valve guide bore is undamaged and dimen-
sions are within correct 12.5 H7 tolerance range:

•

Use original 12.5 U6 (12.533...12.544 mm/
0.4934...0.4939 in) valve guide.

•

Measure valve guides with micrometer.

If valve guide bore is undamaged but slightly
larger than the 12.5 H7 tolerance range:

•

Use replacement valve guide
12.550...12.561 mm (0.4941...0.4945 in).

If valve guide bore is damaged or not to correct
dimensions in 12.5 H7 tolerance range:

•

Use an oversize 12.7U6 (12.733...12.744 mm/
0.5013...0.5017 in) valve guide.

Repair method 1 – ream out the bore (if bore is
damaged or not to correct dimensions)

•

Determine actual diameter of valve guide using
micrometer.

•

Open out bore with Ø12.7 H7 mm
(12.700...12.718 mm/0.5000...0.5007 in) ream-
er.

Repair method 2 – lathe-turn the valve guide (bore
must not be damaged)

•

Determine actual diameter of bore with internal
measuring tool.

•

Calculate the nominal diameter of the valve
guide:

Nominal diameter of valve guide = bore dia. + inter-
ference-fit value (0.015...0.044 mm/
0.0006...0.0017 in).

•

Use an oversize 12.7 U6 (12.733...12.744 mm/
0.5013...0.5017 in) valve guide.

•

Turn down oversize valve guide to nominal di-
mension.

•

Slowly heat cylinder head to 200 °C (392 °F) in a
suitable oven.

•

Immerse valve guide in liquid grinding paste.

•

Freeze valve guide with dry ice.

Caution:

Immediately before pressing in, the temperature
must be –40 °C (–40 °F).

•

Place heated cylinder head flat on workbench or
a similar surface.

•

After cooling, place the valve guide on driving-in
pin, driving-in pin, Ø 5mm (0.20 in),
BMW No. 11 5 673.

•

Insert valve guides into cylinder head with no de-
lay.

•

Allow cylinder head to cool down to room tem-
perature, app. 20 °C (68 °F).

•

Inspect bore in valve guide.

Note:

Valve guides for repair purposes are produced with
an internal diameter of 5.01 mm (0.1972 in) H7.
In most cases, the bore is within the 5.00 mm
(0.1969 in) H7 tolerance range after pressing in.
If the bore is too narrow, ream it out to size.

11.29

Installing valve and valve stem seal

Note:

If a valve was removed, the valve stem seal must be
renewed.

•

Oil the stem when installing the valve.

•

Shrink a short length of tube (arrow) on to the end
of the valve stem.

•

Install the valve stem seal with a 5 mm (0.20 in)
dia. drift, BMW No. 11 5 602.

Caution:

Remove the shrunk-on tube.

•

Fit lower spring plate, valve spring and upper
spring plate.

•

Compress the valve springs with the valve spring
clamp, BMW No. 11 5 690.

Note:

Insert the taper valve collets using grease (to simpli-
fy assembly).

Caution:

Ensure that valve collets are correctly seated in the
valve stem grooves.

•

Relieve tension on valve springs.

•

Check valves for leakage (blow-by).

11 5 690

RS110160

11 5 602

Content .. 5 6 7 8 ..