BMW:

Removing and checking piston (BMW F650GS)

Main
BMW
F-series
F 650 GS
Engine and systems
Engine repair
Removing and checking piston

Contents: Removing piston ↓ Disassembling piston ↓ Determining clearance of piston in…↓ Determining piston ring gaps ↓ Determining piston pin clearance ↓ Assembling pistons ↓

Removing piston

Remove piston pin circlips.

Press out piston pin with drift, BMWNo. 116581.

Note: Mark exhaust-valve side on piston crown.

Disassembling piston

Remove piston rings with piston ring pliers.

Carefully clean piston.

Check piston for signs of damage.

Determining clearance of piston in cylinder

Measure cylinder bore at 55...65 mm (2.17...2.56 in) from the upper edge with an internal micrometer at three points (1, 2, 3).

Make a note of the largest value as dimension "A".

Measure piston diameter "B" at distance H=16 mm (0.63 in) from the lower edge at a right angle to the piston pin axis.

Note: Determine piston clearance: Dimension "A" minus dimension "B" = piston clearance.

Piston clearance:

When new: 0.024...0.040 mm (0.0009...0.0016 in)
Wear limit : max. 0.100 mm (0.0039 in)

Determining piston ring gaps

Slip piston ring 60 mm (2.36 in) into cylinder from top and use a feeler gauge to measure ring gap.

Wear dimension:

Ring gap (all piston rings): 1.0 mm (0.04 in)

Determining piston pin clearance

Measure diameter of piston pin bores in piston stroke direction using an internal micrometer.

Measure both ends of piston pin with micrometer.

Wear limits:

Bore dia. in piston, vertical: max. 22.030 mm (0.8673 in)
Piston pin dia: min. 21.980 mm (0.8654 in)
Radial clearance in piston: max. 0.050 mm (0.0019 in)