Rotary Engine Overhaul Criteria

and

Criteria for Replacement of Parts.

based on a 1978 publication from Mazda.

designed for 1024 * 768

Measurement Method of Compression Pressure:

1. Check the battery is completely charged

2. Warm up the engine.

3. Remove the Trailing plug of the front rotor.

4. Disconnect the primary coil wire on both trailing and leading coils.

5. Install the compression tester hose to the spark plug hole.

6. Have the throttle fully open and crank the engine for 5 - 10 seconds to get the readings.

7. Install the Trailing spark plug on the front Rotor and take the measurement of the rear rotor in the same manner as the front Rotor.

8. Make judgement on the compression pressure.

Judgement criteria for inadequate compression pressure:

Depending apon the battery condition, starter and engine accessories, the cranking speed changes and so does the compression pressure. The graph below shows the relationship between the cranking speed and compression pressure. This is why you can turn your Rotary engine over so easily by hand, often by just turning the alternator pulley.

Criteria For Replacement of Rotary Engine Parts:

1. Rotor Housing:

1.A. Difference in width:

1. Measuring tool required:   Micrometer (50-75 mm) or (75-100mm)

2. Measure the difference in width between A, and the smallest of B, C, or D.

Replace if the difference is more than 0.06 mm (0.0024 in).

1.B. Damages on the trochoid surface:

1.B.a Vertical Scratches on trochoid surface.

1. Inspection - Visual and Sensual Inspecion.

2. Vertical scratches on trochoid surface.

Replace if the depth of scratches is more than 0.02 mm )0.0008 in). As for the vertical scratches of the Rotor Housing edge, the Rotor Housing is re-useable even if the steel base under the chromium plating is exposed, if this has occurred no more than 2mm (0.08 in) from the edge.

1.B.b Chipping of chromium plated surface.

1. Measuring tool required: Vernier calipers or Ruler.

2. Width of chips.

Replace if chipping extends inward more than 2mm (0.08 in).

1.B.c Trochoid surface.

1. Inspection - Visual Inspection.

2. Trochoid surface.

Re-use the housing if there is no other damage than that shown above.

1.C. Corroded wear on the cooling jacket of rotor housing:

1. Measurement tool required - Vernier Calipers.

2. Width of Cooling Jacket at E.

Replace if width E is less than 0.5mm (0.020 in).

Note: Check the Boss area around the spark plug hole and the inside wall of housing, because in rare cases there will be deep corrosion in that area.

Note: When overhauling the engine, install the protector (Part No. 0866 23 0250) to the outside of the inner sealing rubber as shown in image. This will improve the durability of the sealing rubber.

2. Side Housing (Front, Intermediate, Rear):

Note: Even if the side housings are out of the following criteria (2A, 2B, 2C) they can be re-used by regrinding them, unless they have extreme damage due to overheating, engine seizing, or cracking. However the following required finish must be maintained if the housings are reground:

Grinding Precision:

*Less than 0.10 mm (0.004 in) in case with 80 C sprayed layer

2.A Side Housing Distortion.

1. Measuring tools required:  Straight Edge (60cm), Feeler Guage (0.04mm).

2. Area of distortion 1,2,3 & 4.

Limit of distortion - 0.04 mm (0.0016 in).

2.B Side Housing Wear.

2.B.a Stepped wear by Side Seal (Vertical Wear).

1. Measuring tools required:  Dial Indicator (Sharpen tip of guage by grinding), Magnetic Stand.

2. Stepped wear by Side Seal.

Limitation of wear - 0.10 mm (0.0039 in)

2.B.b Stepped wear by Side Seal.

1. Measuring tools required:  Dial Indicator, Magnetic Stand.

2. Stepped wear by Side Seal.

Limitation of Wear:

Inside of Oil Seal tracing mark a - 0.010 (0.0004 in)

Outside of oil seal tracing mark b - 0.10 (0.0039 in)

2.B.c Stepped wear by Oil Seal.

1. Measuring tools required:  Dial Indicator, Magnetic Stand.

2. Stepped wear by Oil Seal.

Limitation of wear - 0.02 mm (0.0008 in).

2.C Scratches on the sliding surface.

1. Measuring tools required:  Dial Indicator, Magnetic Stand.

2. Scratch Area A, B, and C.

Depth limit of scratches:

A - 0.01 mm (0.0004 in)

B - 0.1 mm (0.0039 in)

C - 0.1 mm (0.0039 in)

2.D Fretting and Corrosion.

2.D.a Fretting.

1. Measuring tools required:  Dial Indicator, Magnetic Stand.

2. Fretting Area F.

Limit of Fretting - 0.07 mm (0.0028 in)

2.D.b Corrosion.

1. Measuring tools required:  Dial Indicator, Magnetic Stand.

2. Corrosion Area C.

Depth limit of corrosion - 0.020 mm ( 0.0079 in).

2.D.c Corrosion (Inner Sealing Rubber Contact Area).

1. Measuring tools required:  Dial Indicator, Magnetic Stand.

2. Corrosion Area D.

Depth limit of corrosion - 0.07 mm (0.0028 in)

2.E. Chips around Eccentric Shaft Bore.

Replace if chips are beyond oil seal tracing mark.

3. Rotor:

3.A Clearance related to Rotor (delta-R) .

1. Measuring tools required:  Micrometer (50 - 75 mm) or (75 - 100 mm).

2. Measurement of delta-R. delta-R = Rotor Housing width (A) on A point - Maximum Rotor width (R).

delta-R should be more than 0.1 mm (0.004 in). If delta-R is less than 0.1 mm, hold the rotor by hand or place it on a table with rubber pad, and strike the internal gear lightly with a plastic hammer, being careful not to damage the gear. This is to ensure the gear is seated correctly on its dowels.

3.B Wear on the land of Rotor (delta-H).

1. Measuring tools required:  a. Straight Edge (30cm)         b. Feeler Guage (0.08 mm)

2. Measurement of delta-H.

delta H should be more than 0.08 mm (0.003 in). If delta H is less than 0.08 mm, Replace the Rotor. 

3.C Gap between Apex Seal and Apex Seal groove (delta-G).

1. Measuring tools required:  Feeler Gauge (0.10 mm, 0.15 mm)

2. Measurement of delta-G.

Rarely upper portion of Apex Seal groove is abnormally widened around the Corner Seal groove. In this case, measure the clearance by feeler gauge upon removing corner seal and installing new apex seal as shown below:

If more than 0.2 mm (0.008 in), Replace the Rotor.  **Note: Check the Air Cleaner Element because there is the possibility that a great amount of dust has been entering the Engine.

4. Carbon Apex Seal:

4.A Measurement.

4.A.a Height of Apex Seal (Y).

1. Measuring tools required:  Micrometer (0 - 25 mm).

2. Measurement of Y1, Y2.

Replace if Y1 or Y2 is less than 8 mm (0.31 in).

Apex Seals are individually replaceable.

4.A.b Clearance between Apex Seal and Rotor Housing (delta S) .

1. Measuring tools required:  Micrometer (50 - 75 mm) or (75 - 100 mm).

2. Measurement of delta S. delta S = Rotor Housing width A on (A) point - Apex Seal Length (L).

Note: In previous information, such as the criteria book and workshop manual up to 1975 models, the minimum Rotor Housing width (B, C, or D) has been used as the Rotor Housing width for this measurement (delta S, delta R).

The measuring point has been changed as shown in this manual (A point) from September 1975.

This change is also applicable for all Mazda Rotary Engine including previous models.

The Specification, however, has not been changed by this change in measuring location.

3. Adjusting delta-S

Adjust the delta-S by grinding the Apex Seal end if delta-S is less than the lower limit of the standard delta-S in the criteria.

4.B Apex Seal Inspection.

4.B.a Top of Apex Seal chipped or damaged.

Replace if D is more than 1.0 mm (0.040 in).

4.B.b End of Apex Seal chipped or damaged.

Replace if A is more than 1.0 mm (0.040 in).

4.B.c Vertical grooves on top of Apex Seal.

Re-use unless the height of the Apex Seal is less than 8.0 mm (0.31 in).

5. Metal Apex Seal.

Note: When replacing the two piece type apex seal, replace them as a set (main piece and side piece).

5.A Dimension.

5.A.a Height of Apex Seal (Y).

1. Measuring tools required:  Micrometer (0 - 25 mm).

2. Measurement of Y.

Replace if Y is less than 7.0 mm (0.28 in).

Note: Apex Seals are individually Replaceable.

5.A.b Protrusion of Apex Seal End.

1. Measuring tools required:  a. Visual Inspection      b. Feeler Gauge (0.03 mm).

2. Measurement of Protrusion.

1. Visual Inspection:

2. Measurement by using Feeler Gauge.

Incline Apex Seal slightly to measure it, because protrusion is more evident on the side rather than the top.

When the Rotor Housing is Re-used, reuse the Apex Seal if the clearance is less than 0.03 mm.

When the Rotor Housing is replaced, replace the Apex Seal if any protrusion is found.

5.A.c Apex Seal Distortion (delta-D).

1. Measuring tools required:  Feeler Gauge (0.06 mm).

2. Measurement of delta-D.

Measure the gap between top surfaces of two Apex Seals picked from three seals on one Rotor.

Replace all three Apex Seals on a Rotor if delta-D is more than 0.06 mm (0.0024 in).

5.B Apex Seal Inspection.

5.B.a Top of Apex Seal chipped or damaged.

Replace if D is more than 1.0 mm (0.040 in).

5.B.b End of Apex Seal chipped or damaged.

Replace if A is more than 1.0 mm (0.040 in).

5.B.c Vertical grooves on top of Apex Seal.

Reuse if vertical groove area is less than 1/3 L.

6. Corner Seal.

Note: When replacing the two piece type apex seal, replace them as a set (main piece and side piece).

6.A Corner Seal groove on Rotor.

The corner seal groove of the Rotor shall be checked by the bar limit gauge (Go - No Go gauge) and classified into three conditions.

1. Measuring tools required: Bar limit gauge (TKK special tool No. 49 0839 165, MMA No. 4908 39 1650)

.

2. Classification

3. Measuring Method.

a. Do not force the gauge into the groove.

b. Gauge should be put vertically into the groove.

**Note:   An oversize Corner Seal for the expansion type corner seal is not available. However, the standard size corner seal of the expansion type can also be used for class- "b" (go-end of the gauge can only go into the groove). If both ends of the gauge go into the groove (class - "c"), replce the Rotor.

7. Side Seal.

7.A Gap between Side Seal and Corner Seal (delta-E).

1. Measuring tools required:  Feeler Gauge (0.05 and 0.4 mm).

2. Measurement of delta-E.

8. Oil Seal.

8.A Width of Oil Seal surface contacting Side Housing.

1. Measuring tools required: a. Magnifying glass      b. Vernier Calipers (0 - 150 mm).

2. Measurement of A.

Replace if A is more than 0.5 mm (0.020 in).

8.B Chipping of Chromium edge.

Replace if A is more than 2.5 mm (0.1 in) or the number of surface chips exceeds 10.

Note: When installing the inner Oil Seal, utilize an old Oil Seal as shown in the figure to fully seat the Oil Seal:

9. Seal Spring.

9.A Stroke of Seal Spring.

1. Measuring tools required: Vernier Calipers (0 - 150 mm).

2. Measurement of stroke A, B, C and height D.

9.B Thickness of Seal Spring.

1. Inspection: Visual Inspection.

A, B, C, D    -   Replace spring if less than half of new one.

10. Eccentric Shaft.

10.A Eccentric Shaft runout.

1. Measuring tools required: a: "V" Blocks      b: Dial Indicator and stand      c: Flat Surface

2. Runout of point A.

Replace if Runout is more than 0.06 mm (0.0024 in).

10.B Bearing clearances.

10.B.a Rotor Bearing clearances.

1. Measuring tools required: a: Micrometer (50 - 75 mm)      b: Inside Micrometer (50 - 75 mm)

2. Measurement of point a, b, and c.

    Rotor Bearing Clearance = (c - a) or (c - b)

If the Rotor Bearing clearance is more than 0.1 mm (0.0039 in), replace the eccentric shaft or the Rotor Bearing.

10.B.b Main Bearing clearance.

1. Measuring tools required: a: Micrometer (25 - 50 mm)      b: Inside Micrometer (25 - 50 mm)

2. Measurement of a, b, and c.

    Main Bearing Clearance = (c - a) or (c - b)

If the main bearing clearance is more than 0.10 mm (0.0039 in), replace the eccentric shaft or Main Bearing.

10.B.c Journal Surface of Eccentric Shaft.

    Eccentric shaft shall be reused except in the case of Rotor Bearing Seized or heavy scratches, if the measurement is within limits. Refine the journal surface of the Eccentric Shaft carefully by using emery paper ( # 1000) with engine oil, if the Journal Surface is slightly seized or scratched.

11. Oil Pump drive Chain.

11.A Protrusion of chain adjuster.

1. Measuring tools required: Vernier Calipers or Ruler.

2. Measurement of Protrusion.

Note: Check the protrusion during disassembly to avoid wasting time when assembling the engine.

12. Spacer.

12.A Eccentric Shaft end play.

1. Measuring tools required: a. Dial Indicator and magnetic stand     b. Micrometer (0- 25 mm)

2. Measurement of End Play.

                Note:    (1)  If the end play is small, spacer is small.

                               If the end play is big, spacer is big.

                          (2) The Spacers are available in the following thickness.

                         (3) Check the end play before Engine Overhaul and take note of the reading, to make it easier when assembling the engine.

Technical Data:

*1: Outside of Oil Seal Tracing Mark.

*2: Inside of Oil Seal Tracing Mark.

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