Attention! Determine the position of each removed part. Lay out the parts according to their belonging (for example, intake or exhaust) so that they can be assembled in their original position.
Camshaft
Both shafts should be checked for journal runout and also for cam and journal wear if abnormal noise or vibration or lack of power is noted during engine operation. All of these can be caused by cam wear or profile changes beyond what is acceptable.
(1) Exhaust camshaft; (2) Intake camshaft
Automatic decompressor
Check the decompressor weight for mobility manually. If there is any jamming, replace it with a new one.
Warning! Do not attempt to disassemble the camshaft and decompressor. These components cannot be repaired.
Cam wear
Cam wear is often the cause of valve timing shifts, which results in reduced engine power.
Measure the cam lobe height with a micrometer. If the cam lobe is worn beyond the acceptable limit, replace the camshaft with a new one.
09900-20202: Micrometer (25-50 mm).
Cam height limit (N):
- Intake valve: 35.02 mm
- Exhaust valve: 34.92 mm
Camshaft cam wear
With the camshafts installed, measure the clearance using plastic gauges.
09900-22301: Plastic gauge
09900-22302: Plastic gauge
Clearance in camshaft bearings (inlet and outlet) permissible gap: 0.150 mm
Tighten the cover bolts evenly and crosswise to the specified torque.
Bolt tightening torque: 10 Nm (1.0 kgf·m).
Note: Do not rotate the camshaft with the plastic gauge installed. Remove the caps and determine the width of the compressed plastic gauge on the scale. Measure at the widest part of the compressed plastic gauge. If the clearance exceeds the permissible limit, measure the inside diameter of the cap and the outside diameter of the journal. Replace the camshaft or cylinder head, depending on which is causing the increased clearance.
09900-20602: Dial indicator (1/1000 mm)
09900-22403: Bore gauge for measuring small diameters
Inner diameter of the lid (INLET and OUTLET). Standard: 22.012–22.025 mm
09900-20205: Micrometer (0–25 mm)
Neck diameter (INLET and OUTLET). Standard: 21.959–21.980 mm
Neck beating
Mount the shaft on the prisms and measure the runout using a dial indicator. If the runout exceeds the permissible limit, replace the camshaft with a new one.
09900-20607: Dial indicator (1/100 mm)
09900-20701: Magnetic stand
09900-21304: Prisms (100 mm)
Neck runout: Maximum permissible runout: 0.10 mm
Timing chain tensioner
The timing chain tension is maintained by an automatically adjustable regulator. Insert a flat-blade screwdriver into the regulator slot and turn it clockwise to loosen the tension, remove the screwdriver to check for progressive movement of the tensioner rod. If the rod sticks or the spring mechanism does not work, replace the regulator assembly with a new one.
Timing chain guide and chain tensioner
Check the timing chain guide and tensioner for wear and damage. If damaged, replace them with new ones.
Cylinder head inspection
Remove pusher 1 and washers 2 manually or with a magnetic device.
Using a special tool, compress the valve springs.
Remove the crackers (3) from the valve stem.
09916-14510: Valve Puller
09916-14521: Puller Accessory(spring compression bushing)
09916-84511: Tweezers
Remove the valve washers (4) and springs (5).
Remove the valve from the other side.
Oil seals (6) with needle-nose pliers.
Remove the spring seat (7).
Cylinder head deformation
Clean the combustion chamber from carbon deposits.
Check the mating surface of the head for flatness using a straightedge and feeler gauge. Take measurements in several places. If the gap in any place exceeds the permissible value, replace the head with a new one.
09900-20803: Probe
Tolerance limit for flatness: 0.05 mm
Permissible runout: 0.05 mm
Valve chamfer wear
Visually inspect the valve bevels for wear and damage. If defects are found, replace the valve with a new one. Determine the belt width (T). If it is less than the permissible value, replace the valve with a new one.
Belt width (T).
Tolerance limit: 0.5mm
Permissible runout: 0.05 mm
Valve stem runout
Place the valve on the prisms and measure the runout using the indicator as shown in the figure. If the runout value exceeds the permissible value, replace the valve with a new one.
09900-20701: Magnetic stand
09900-20607: Dial indicator (1/100 mm)
09900-21304: Prisms (100 mm)
09900-20701: Magnetic stand
Permissible runout: 0.05 mm
Radial runout of valve head
Place the valve on the prisms and measure the radial runout of the head using an indicator, as shown in the figure. If the runout value exceeds the permissible value, replace the valve with a new one.
09900-20607: Dial indicator (1/100 mm)
09900-20701: Magnetic stand
09900-21304: Prism (100 mm)
Head radial runout tolerance: 0.03 mm
Valve stem play
Raise the valve approximately 10 mm above the seat. Measure the play along the stem in two mutually perpendicular directions "X" and "Y". Position the indicator as shown in the figure. If the play exceeds the permissible value, determine what should be replaced - the valve or the guide bushing.
09900-20607: Indicator (1/100 mm)
09900-20701: Magnetic stand
Maximum allowable clearance: 0.35 mm
Valve stem wear
Measure the valve stem diameter with a micrometer. If the diameter exceeds the permissible limits, replace the valve with a new one. If the stem diameter is within the tolerance, and the clearance exceeds the permissible limits, replace the guide bushing. After replacement, check the clearance.
09900-20205: Micrometer (0-25 mm)
Rod diameter tolerance:
- Inlet valve: 4.475–4.490 mm
- Exhaust valve: 4, 455–4, 470 mm
Valve sleeve inspection
Press out the bushing using a special tool.
09916-43210: Bushing Removal/Installation Tool
Note.
- Do not reuse removed bushings.
- As a replacement, use only bushings with repair dimensions on the outside diameter.
- Ream the hole in the cylinder head for the bushing using a special reamer with a handle.
09916-34580: Special reamer (10.8 mm)
09916-34542: Reamer Handle
Lubricate the bushing with oil and press it into the head using a puller.
09916-43210: Guide Bushing Puller
09916-43220: Guide Bushing Puller Part
Caution: Failure to lubricate the guide bushing before pressing it in may result in damage to the head or bushing.
After installing the guide bushings, ream their holes with special reamers. After reaming, clean the holes.
09916-33210: Bushing Reamer (4.5mm)
09916-34542: Reamer Handle
Valve seat width
Cover the valve seat evenly with Berlin glaze. Install the valve in place. Press the valve to the seat with a special device and turn it so that a clear imprint remains on the chamfer at the contact point.
09916-10911: Valve lapping tool
The annular imprint on the valve chamfer must not have any breaks. In addition, its width must comply with the standard.
Landing belt width (W). Standard: 0.9–1.1 mm
If there are any deviations in size, grind the chamfer.
Valve seat maintenance
The inlet and outlet valve seats are machined at three different angles. The contact surfaces are machined at an angle of 45°.
| Inlet | Release | |
| 45° | N-122 | N-122 |
| 15° | — | N-121 |
| 30° | N-126 | — |
| 60° | N-111 | — |
For the USA:
- Seat cutters: N-111, N-121, N-122 and N-126
- Mandrel: N-100-4.5
For other countries:
- 09916-21111: Set of cutters (including N-111, N-121 and N-122)
- 09916-20630: Roller burr for N-126 saddle
- 09916-20640: Mandrel N-100 - 4.5
Note: Use the N-100-4.5 mandrel with the N-111, N-121, N-122, and N-126 cutter set.
Attention! The contact surface of the seats must be checked after each treatment.
When installing the mandrel (1), turn it slightly.
Fit the mandrel tightly. Use the 45° burr (2), mandrel (3) and handle (4).
Pre-treatment of the saddle
Clean off any carbon deposits and renew the surface using a 45° burr. Make 1–2 turns.
Measure the saddle width (W) each time.
If the saddle is pitted or burnt, go deeper into the saddle.
Note: Only trim the minimum necessary to prevent replacing the shims used to adjust cam clearance.
Processing to narrow the contact zone of the saddle
If the contact surface on the valve is too high or the band is wider than allowed, use a 30° roller cutter (for intake valve) and 15° (for graduation), to lower or narrow the contact surface
The contact surface is located too high on the valve chamfer or the belt is too wide
Final processing of the saddle
If the contact surface is too low or too narrow, use a 60° cutter (for intake valve), to raise and widen the contact band. If the band is too high or too wide, use a 15° burr (for graduation) and 30° (for intake) valves to lower or narrow the contact belt.
Once the desired width and location of the belt has been achieved, lightly rough the surface with a 45° burr to remove any burrs remaining from the previous processing.
The contact surface is located too high on the valve chamfer or the belt is too wide
Caution! Do not use lapping paste after final finishing. The final finished valve seat should have a velvety surface, but not polished or shiny. This will provide the necessary flexibility for proper valve seating, which will occur during the first seconds of engine operation.
Note: After machining the valve seats, be sure to check the valve clearance after assembling the cylinder head (see 2-5).
Checking the valve seating tightness
With the valves and springs installed, pour some gasoline into the intake or exhaust tract. Make sure that gasoline does not pass through the valves. If leaks are detected, repair the sealing surface.
Warning! Gasoline is highly flammable and explosive. Keep away from sparks, heat and flames.
Valve spring
The spring force holds the valve tightly in place. Weak springs result in reduced engine power and cause a rattling noise from the valve train. Check the valve springs for proper force by measuring their free length and the force required to compress them. If the spring length is less than the specified limit or the spring force is outside the specified limit, replace the inner and outer springs as a set.
 |  |
Tolerance for the length of valve springs in a free state (INLET and OUTLET):
- For inner spring: 38.6 mm
- For outer spring: 40.6 mm.
Spring compression force tolerance (INLET AND OUTLET):
- For inner spring: 48-58 N (4.9-5.9 kgf) at 29.9 mm length
- For outer spring: 133–153 N (13.6–15.6 kgf) at 33.4 mm length
Assembly
Install the spring seats (1).
Apply molybdenum grease to the valve stem seals (2) and press them into place.
Caution: Do not reuse valve stem seals.
Apply molybdenum grease to the valves as shown in the figure, then insert them into the guide bushings.
Caution: When reinstalling the valves, be careful not to damage the sealing edges.
Install the valve springs with a smaller pitch (A) towards the cylinder head. (B) A larger pitch. (C) Down.
 |  |
Install the valve washer by compressing the springs with a puller. Install the cotters halves and release the springs so that the cotters (1) fit between the washer and the valve stem. Make sure that the rounded projections (2) of the cotters fit tightly into the groove at the end of the valve stem.
09916-14510: Valve Puller
09916-14521: Puller Accessory
09916-84511: Needle nose pliers
 |  |
Caution: Install parts in their original positions.