Minimoto Garage - Piston Ring Replacement

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Tech Tips from Racers for Racers
Step by Step
Piston Ring Replacement
(Note: The pictures shown below are of a Polini 6.2hp water-cooled engine, but the basic steps are the same on all minimoto engines.)
Step 1.
You will need to drain your coolant and remove your engine before doing the following steps. Please visit the following tips to learn how:
Step by Step: Radiator Draining
Step by Step: Engine Removal

You might also want to remove the spark plug for this tip.

Step 2.
Remove the head bolts, you'll need a 10mm socket or wrench.

Step 3.
Remove the head.

Step 4.
Remove the cylinder.

Step 5.
This is what the engine looks like with the head and cylinder removed.

Step 6.
Here is a picture of the piston ring. This is what will replace the current one.

Step 7.
Remove the current piston ring.

Step 8.
Install the new piston ring.

Step 9.
Squeeze the piston ring with your fingers and ease the piston into the cylinder as shown. Make sure the piston is as straight as possible. You also want to pay close attention to where the two ring ends meet. There is a little notch on the back of the piston and shows where they should meet.

Step 10.
Replace the cylinder.

Step 11.
Replace the head.

Step 12.
After you have put the cylinder and head back on, finger tighten the head bolts then grandually and evenly torque them to 0.8kgm (5.78ft/lbs or 69.36in/lbs).

Now you're all done and ready to put the engine back into the chassis.
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