DIY Renesis Engine Rebuild Resource

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Inspection

Inspection can be divided into four parts: rotors, housings, side irons (or side housings) and eccentric shaft. Before inspection, you’ll need to unbolt and remove the front and rear stationary gears.

Rotors:

Each rotor consists of the following:

  • 3 apex seals and 6 apex seal springs
  • 6 side seals and side seal springs
  • 4 circular oil seals with springs and o-rings
  • 2 circular compression cut-off seals with springs
  • 1 rotor bearing
  • 6 corner seals, with plugs and springs

As a note, you’ll want to store everything you remove in such a way that you can identify it’s exact position on it’s rotor while on the bench. Start by removing the apex, corner and side seals and their respective springs. Then carefully remove the circular oil and compression seals with a pair of small flat-bladed screwdrivers. Again, you’ll need to know which rotor/side/face these parts came from when measuring. Additionally, label each rotor (front/rear) because they may be balanced differently. Finally remove the rotor bearings with a shop press.

Clean the rotors and seals before measurement. If you don’t have a parts washer (links to parts washers on the Links page), you can remove the carbon and grease with a combination of parts solvent, brake parts cleaner, picks and screwdrivers. Be careful not to damage the rotor while cleaning. You’ll want to clean the grooves for all of the seals and gently clean the rotor faces and sides.

bearing scoring

There are four rotor areas to inspect to ensure the rotor is ready for additional service. If the rotor fails any of these inspections, replace the rotor. First, use a micrometer to measure the clearance between the rotor and side housing. This is done by measuring the width of the rotor housing, and subtracting the width of the rotor (as measured from the inside with the micrometer against the rotor round). The difference between side housing width and rotor width must be between .0020”-.0074”.

Then measure the protrusion of the rotor round by placing a machinist’s straight-edge on the side of the rotor in alignment with one of the three rotor apexes. Use a feeler gauge to measure the gap between the rotor face and the straight-edge. This should be between .0048”-.007”. Do this for each of the three apexes, on each of the four rotor faces.

Then, measure the width of the corner seal grooves using an inside micrometer. If the width is >= .43488”, replace the rotor. If the width is between .43381”-.43488” use a .03mm oversized corner seal. Otherwise the corner seal groove is ok and the rotor is ok. Repeat this for all 12 corner seal grooves.

Finally, measure the apex seal side groove width by using a feeler gauge to measure the gap between the side of a clean apex seal and the rotor. If the clearance exceeds .0017”-.0039” replace the apex seal. If clearance exceeds those specifications with a new apex seal, replace the rotor. You can also inspect oil seals, side seals and apex seals for reuse, but I would generally recommend replacing these (and their springs) while you’ve got the engine apart.

rotor housing scoring rotor housing width measurements

Rotor Housings:

Rotor housings receive a visual inspection to check for scoring, flaking or discoloration (above top). If any of these are observed, it’s recommended to replace the housing. Use a micrometer to measure the difference in width of the housings in four places (above bottom). If the difference between A and any other locations is > .0024”, replace the housing.

Side Housings:

Side housings should be measured for flatness in several areas using a machinist’s straight-edge. If any measurement is out of specification, the corresponding housing should be replaced. Some rebuilders have been successful with having these machined, but removing more than .0025” will require the housing to be re-nitrided. First, measure each of the four side housing faces for > .0016” of distortion along the four planes demonstrated. Then use a dial gauge to check the following areas for wear.

  • Vertical Wear: >.0039"
  • Convex Oval Oil Seal Paths (A > .0004", B > .0039")
  • Oil Seal Stepped Path Wear > .0008"
side housing perimeter measurement side housing measurement side housing measurement side housing measurement

Eccentric Shaft

The eccentric shaft should be placed on v blocks and main journal runout should be measured with a dial indicator. If runout exceeds .0024” replace the eccentric shaft. Additionally, inspect the eccentric shaft oil shaft for clogging and clean with compressed air if necessary.

Before reassembly, you’ll want to press new bearings into the front and rear stationary gears, and rotors. There are links to service tools for pressing these bearings in/out of rotors and gears on our links page. You will also want to replace the front and rear oil seals after replacing the bearings, and ensuring proper eccentric shaft oil clearance.

To measure eccentric shaft oil clerance, you’ll need to measure the difference in eccentric shaft journal outside diameter and bearing inside diameter to calculate bearing oil clearance. If the clearance is > .0039”, replace the rotor bearing. If the clearance is too great, even with larger bearings, replace the eccentric shaft. Perform the same procedure with main bearings, replacing if clearance is > .0039”

Finally, replace the pilot bearing in the rear of the eccentric shaft. You can return your pilot bearing to service with new lubrication if the needle rollers spin freely and smoothly, but it’s best if this is simply replaced while it’s convenient.