Polaris RZR 900XP Engine Rebuild Part 5: Bottom End Rebuild

This is the fifth part of our Polaris RZR 900XP engine rebuild series, in which we highlight the important points of the process of rebuilding the bottom end of the Polaris UTV

Watch our Polaris RZR engine rebuild video above and follow the steps below to rebuild the bottom end of the side-by-side's engine. The steps covered include:

  • Sizing the bearings
  • Replacing connecting rods 
  • Installing pistons
  • Installing the crankshaft
  • Reassembling the crankcase
  • Reinstalling the oil system

Polaris RZR 900 XP bottom end rebuild

In addition to watching the Polaris RZR 900 engine rebuild video a couple of times, we also recommend referencing our Polaris RZR XP exploded parts diagrams, which show how all the various components come apart and fit back together again.

Tools and Parts Needed - Polaris RZR 900XP Bottom End Rebuild

Tools 

  • Ratchet and extensions
  • Socket set
  • Pick tool
  • Dead-blow hammer
  • Torque wrench

Parts

  • Connecting rod
  • Crankshaft
  • Piston kit
  • Sealant
  • Circlip

 

  • Camshaft roller chain
  • Oil pump drive chain
  • Oil pump seal
  • Flange seal
  • Gasket

NOTE: The list of parts will vary depending on what needs to be replaced in your RZR's engine. The full list of parts used for this rebuild can be found here.

Sizing the Bearings - Polaris RZR 900XP

Step 1. To correctly size the bearings for your RZR's motor, you'll need the six-digit crankcase bearing identification number stamped on the end of the crankcase, and the six-letter crankshaft bearing identification code stamped on the end of the crankshaft. 

Polaris RZR bearing sizing diagram

NOTE: Correctly sizing the bearings is a vital step to rebuilding the bottom end of an RZR motor, and we suggest you read the how to size Polaris RZR 900XP crankshaft bearings step-by-step guide.

Watch the clip below to see the bearing sizing segment of our Polaris RZR 900XP engine rebuild video.

Replacing Connecting Rods - Polaris RZR 900XP

Step 2. When replacing a connecting rod, make sure you orient it in the same way as the old one came out of the engine. In other words, the serial number on the connecting rod should face the same direction as the original.

Polaris RZR engine connecting rod

Watch the clip below to see connecting rod replacement segment of our Polaris RZR 900XP engine rebuild video.

Replacing Piston Rings - Polaris RZR 900XP

Step 3. When replacing or reinstalling the piston rings, make sure you orient them in the correct way, with the gaps in the rings rotated to their allotted positions.

Polaris RZR piston ring diagram

Watch the clip below to see the piston ring replacement segment of our Polaris RZR 900XP bottom end rebuild video.

Installing Pistons - Polaris RZR 900XP

Step 4. When installing the pistons into the cylinders, make sure the delta-T mark on each piston is facing the exhaust side of the cylinder block.

Watch the clip below to see the piston replacement segment of our Polaris RZR 900XP engine rebuild video.

Installing the Crankshaft - Polaris RZR 900XP

Step 5. Before installing the crankshaft into the top half of the crankcase, you must reinstall the oil drain diverter into the crankcase and install the output seal, the oil timing chain and the cam timing chain onto the crankshaft. 

Step 6. Once the crankshaft is installed, the four connector rod bolts must be torqued in two stages: first to 13-foot pounds, then tightened at an additional 105-degree turn.

Polaris RZR 900 engine rebuild crankshaft

Step 7. Align the mark on the crankshaft gear with the mark on the counterbalance shaft gear.

Polaris RZR 900 XP crankshaft gear alignment

Watch the clip below to see the crankshaft installation segment of our Polaris RZR 900XP engine rebuild video.

Reassembling the Crankcase - Polaris RZR 900XP

Step 8. Make sure you don't apply sealant to the two oil passages carved into the crankcase mating surfaces.

Polaris 900XP RZR crankcase assembly

Step 9. The eight M10 crankcase bolts should be tightened in the sequence shown below. The bolts must first be torqued to 21-foot pounds, then tightened by an additional 90-degree turn. The two M8 crankcase bolts should be torqued to 26-foot pounds.

Polaris 900XP RZR crankshaft bolts

Step 10. The two 12mm bolts in the upper crankcase should be torqued to 26-foot pounds, and the eleven 8mm bolts in the upper crankcase should be torqued to 89-inch pounds.

Watch the clip below to see the crankcase reassembly segment of our Polaris RZR 900XP engine rebuild video.

Reinstalling the Oil System - Polaris RZR 900XP

Step 11. Install the oil pump. Don't forget to install the two dowels under the oil pump before bolting it into place. The three oil pump bolts should be torqued to 89-inch pounds.

Polaris RZR 900XP oil system install

Step 12. Reattach the oil sump cover. The fifteen 8mm sump cover bolts should be tightened in the sequence shown below. The bolts should be torqued to 106-inch pounds.

Polaris RZR 900 oil sump cover

Watch the clip below to see the oil system reassembly segment of our Polaris RZR 900XP engine rebuild video.

The next stage in this Polaris RZR 900 engine rebuild project will be to rebuild the top end. Watch the Polaris RZR 900 Engine Rebuild: Part 6 video below.

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