Crank, Pistons and Rods, Measurement
Special Tools:
- Counterhold tool No. 999 2413, or equivalent
- Drift tool No. 999 5309, or equivalent
- Magnetic Stand tool No. 999 9696, or equivalent
- Dial Gauge tool No. 999 9684, or equivalent
- Micrometer tool No. 999 9701, or equivalent
- Micrometer tool No. 999 9702, or equivalent
- Micrometer tool No. 999 9703, or equivalent
- Micrometer tool No. 999 9704, or equivalent
Universal Tools:
- tool No. 998 5424, or equivalent
NOTE:
- For additional information on special tools and equipment used in this procedure, refer to "Tools For Engine Reconditioning". Tools and Equipment
- Crank mechanism, measurement: Steps 1 through 12
- Connecting Rods bushings, replacement: Steps 13 through 16
- Connecting Rods, replacement: Step 17
Procedure
1. Measure crankshaft:
- Use micrometer tool No. 999 9703.
- Measure out-of-round and ovality of bearing journals.
- Take readings at several points around circumference and along length.
2. Crank pins:
- Diameter:
Standard: 50.000 mm +0 or -0.016
Undersize: 49.750 mm
- Bearing Seat Width: 26.000 mm ± 0.1
- Max. Out-of-round: 0.004 mm
- Max. Taper: 0.004 mm
Main bearing journals:
- Diameter:
Standard: 65.000 mm +0.003 or -0.016
Undersize: 49.750 mm
- Bearing Seat Width: 26.000 mm +0 or -0.04
- Max. Out-of-round: 0.004 mm
- Max. Taper: 0.004 mm
3. Check straightness of crankshaft:
- Use dial gauge tool No. 999 9684 and magnetic stand tool No. 999 9696, or equivalent.
- Put crankshaft with the outermost main bearing journals in the V-blocks.
- Turn crankshaft and measure radial throw of other main bearing journals.
- Max. Radial Throw (All): 0.032 mm
4. Remove piston rings:
- Use piston ring pliers tool No. 998 5424, or equivalent.
- Remove carbon deposits.
Clean piston ring grooves by scraping with a broken off ground section of piston ring.
- Check for:
Damage.
Wear.
Cracking.
5. Check piston ring axial clearance:
- Use new rings.
- Upper compression ring: 0.05-0.085 mm
- Lower compression ring: 0.03-0.065 mm
- Oil scraper ring: 0.02-0.055 mm
Dimensions, version 1
- Upper compression ring: 1.5 mm
- Lower compression ring: 1.75 mm
- Oil ring: 3.0 mm
Dimensions, version 2
- Upper compression ring: 1.2 mm
- Lower compression ring: 1.75 mm
- Oil scraper ring: 3.0 mm
6. Measure piston diameters:
- Use micrometer tool No. 999 9704, or equivalent and sliding calipers.
- A = Overall piston height.
- B = Height from wrist pin center to crown.
- C = Piston diameter must be measured at right-angles to wrist pin hole and at distance C from edge of skirt.
- D = Diameter.
- Dimensions A, B and C, see table.
Piston diameter: (D)
- Standard
Piston marked C: 82.98-82.99 mm
Piston marked D: 82.99-83.00 mm
Piston marked E: 83.00-83.01 mm
Piston marked G: 83.017-83.032 mm
- Oversize
OS1: 83.177-83.192 mm
OS2: 83.377-83.392 mm
NOTE: Max. difference in weight between pistons in same engine: 10 g
7. Calculate piston clearance:
- Measured:
Cylinder diameter minus Piston diameter = Piston clearance.
Permissible piston clearance: 0.01-0.03 mm
NOTE: Measurement of cylinder bore as per steps 1 through 3 of "Cylinder Block, Measurement".
8. Separate connecting rods and pistons:
- Check that each piston and connecting rod is marked before separating.
NOTE:
- Piston markings: Scrape wrist pin clean.
- Mark with felt-tip pen cylinder no. and an arrow towards the front end of the engine if marking is unclear.
- Connecting Rods markings: as per step 4 of Crank, Pistons and Rods Dismantling at Dismantling, Cleaning, Inspection.
- Pry circlip out carefully with a screwdriver. Push wrist pin out by hand. Clean and inspect connecting rods, bearing caps and bolts for damage, wear and cracking. Check length of connecting rod bearing cap bolts using sliding calipers.
- Max. length: 55 mm
9. Check Wrist pin fit in pistons:
- Wrist pins must not have any play, but should slide through hole without play when pressed by hand.
- Replace piston if there is any play.
10. Check wrist pin fit in connecting rods:
- Wrist pin should slide through hole easily under thumb pressure. If excessive play, check wrist pin dimensions and change little end bushing if necessary.
- Use micrometer tool No. 999 9701, or equivalent.
Wrist pin diameter:
B 5202-5254: 23.0 mm +0 or -0.004
11. Check Conrod (big end) bearing seats:
- Check bearing shells visually.
- If any doubt, measure out-of-round.
- Use dial gauge 999 9639, or equivalent.
Bearing seat diameter:
B 5202-5254: 53.0+0.013 mm
Max. Out-of-round: 0.006 mm
12. Check Conrad in alignment gauge
- Check for straightness and twisting.
Important:
- Check that clamping surface of fork is round and free of burrs.
- Release and tighten expander at big end between each alignment check.
Connecting Rods Bushings, Replacement
13. Press bushing out:
- Use drift tool No. 999 5309, or equivalent.
- Use drift the right way round, with the short end downwards.
- Use drift tool No. 999 2413, or equivalent as counterhold.
14. Press in new bushing:
- Use drift tool No. 999 5309, or equivalent.
- Use drift the right way round, with long end downwards.
- Push drift right down.
NOTE: Make sure that hole in bushing lines up with lubricating passage in connecting rod.
15. Check wrist pin fit in new bushing:
- Wrist pin should slide through bushing without noticeable play when pressed gently with thumb.
- Adjust bushing as required.
16. Check connecting rod in alignment gauge:
- Check for straightness and twisting.
NOTE:
- Check that clamping surface of fork is round and free of burrs.
- Release and tighten expander at big end between each alignment check.
17. Connecting Rods, replacement:
- Connecting Rods are symmetrical and can be turned over if required.
- Markings: Assemble connecting rod, tighten bolts to 20 Nm (15 ft lb) and check that bearing end is turned the right way.
- Put big end in a vice with copper inserts or similar.
Mark both halves with cylinder number using a number punch or die.