Removing and Installing Chain Tensioner

Tightening Specifications:

NOTE:
The hydraulic chain tensioner is supplied with pressurized oil through an oil duct (4) in the front of the crankcase and in the cylinder head (arrows).





The contact pressure of the thrust pin (10) on the tensioning rail is maintained at a constant pressure by the non-return valves (4 and 5) and the pressure limiting valves (6 and 8) together with the compression spring, irrespective of engine oil pressure.

Ventilation is performed once the oil pressure has built up in the engine oil circuit and the chain tensioner is filled with oil.





1 Closing nut
2 A 25 x 30 aluminium seal
3 Spherical seat ring
4 5 mm dia.ball
5 Ball cage
6 Valve disc
7 O-ring
8 5mm dia.ball
9 Compression spring
10 Thrust pin
11 Compression spring
12 Housing
13 B16 snap ring

Since June 1980 a chain tensioner with a reinforced flange (17 mm before 12 mm) has been installed. Fit on chain tensioner with 17 mm thick flange with M 8 x 30 bolts (previously M 8 x 25).





The dimensions of the chain tensioner housing and of the closing nut have been modified. Production break- point October 1981. These measures were taken to counter fractured, leaking closing nuts.

Chain tensioner housing: Size 1.2-02 was 1.5 mm.
Closing nut: size 15.5 + 02 was 14.5 mm.





1 Closing nut
2 Aluminium seal
3 Spherical seat ring
4 5mm dia. ball
5 Compression spring
6 Ball cage
7 Filler piece
8 Valve disc
9 O-ring
10 5 mm dia. ball
11 Compression spring
12 Thrust pin
13 Compression spring
14 Housing
15 Circlip

An additional filler piece (7) in the compression spring reduces the pressure chamber volume and limits the return travel of the thrust pin (12) so that the chain tensioner responds more rapidly.

Moreover, the pressure is built up more rapidly by an additional compression spring (5) in the pilot valve.

Chain tensioners with this technical further development (see images below for series production breakpoint) should be used to deal with complaints of noise and when repairing the chain drive, also on engines manufactured prior to this date.

Production Breakpoint: October-December 1987 (filler piece and compression spring)




Series Production Breakpoint: February 1989 (filler piece and compression spring)





Removing and Installing:
1 Unscrew the securing bolts and take off chain tensioner.
2 Install chain tensioner with new gasket and tighten bolts evenly.
The thrust pin of the chain tensioner must be resting on the lug of the tensioning rail.

NOTE: For repair purposes, the chain tensioner should be replaced complete.