BMW R 1100 GS + Adventure, Repair Manual

Page: 114 / 464

11.64
Replacing valve guides
•
Heat cylinder head slowly and uniformly to
200
°
C in a suitable oven.
e
Caution:
Wear protective gloves when handling heated parts.
•
Drive out valve guides with 6/5 mm
(0.236/0.197 in) dia. extractor pin,
BMW No. 11 5 672/674 , from the combustion
chamber side.
•
Allow cylinder head to cool down to room tem-
perature (app. 20
°
C).
•
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).
L
Note:
Valve guides are installed in the cylinder head with
an interference fit of 0.015...0.044 mm
(0.00059...0.00173 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) (0.5...0.50071 in) reamer.
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)
(0.00059...0.00173 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 in a suitable
oven.
•
Immerse valve guide in liquid grinding paste.
•
Freeze valve guide with dry ice..
e
Caution:
Immediately before pressing in, the temperature
must be –40 °C.
•
Place heated cylinder head flat on workbench or
a similar surface.
•
Attach chilled valve guide to 6/5 mm
(0.236/0.197 in) dia. pressing-in arbor
BMW No. 11 5 671/673 .
•
Insert valve guides into cylinder head with no de-
lay.
•
Allow cylinder head to cool down to room tem-
perature, app. 20
°
C.
•
Inspect bore in valve guide.
L
Note:
Valve guides for repair purposes have an internal di-
ameter of 6.01 H7 mm (5.01 H7 mm/R 850).
In most cases, the bore after pressing in the valve
guide is in the 6.00 H7 mm (5.00 H7 mm/R 850) tol-
erance range.
If the bore is too narrow, it should be opened out.