This article is one of a series which describes how to disassemble, work on, and reassemble the Road Star engine. This particular article shows how to install pistons, and cylinders. See the Complete Engine Tear Down, Orientation article in this website for details of other aspects of engine details.

Be sure you refer to the service manual through all phases of this project.

Some pistons are now made with very sophisticated coatings and finishes on them which can be delicate until cured during service. Therefore, unless you’re sure it’s OK, don’t use solvents to clean them. Wash the pistons with warm, soapy water. Rinse thoroughly, and blow dry.

Clean the wrist pins with solvent, and dry.

New piston rings must have their gaps measured and gapped so as to be sure they have room to expand under heat--within limits. To measure, adjust, and install them, start by oiling one piston, and one cylinder wall.

Rub the rings for that piston with oil. Be careful; they are somewhat delicate--especially the expander (squiggly one).

Turn the cylinder on its side, or upside down. Then carefully slide the piston--top-first--into the bottom of the cylinder.

Lift the cylinder and piston upright, and position them with your hand under the bottom of the cylinder and supporting the piston.

Side Note: I must say, as I sat on my folding chair in my garage with my hand stuck up the bottom of the cylinder, I felt like a ventriloquist with my hand inside a dummy.

Now push one of the thin piston rings into the top of the cylinder, down about 3 or 4 inches. Raise the piston up to the ring, and push the piston and ring against each other so that the ring lies squarely in the cylinder, at a height about 1 to 2 inches below the cylinder top.

The photo below demonstrates the result, but do not start with the expander (squiggly) ring.

Push the piston down a bit, without disturbing the ring. Then set the cylinder on a bench--right side up.

Measure the gap with a feeler gauge, and adjust as needed, per instructions from the manufacturer or the service manual. Widen the gap of each ring with a small, flat file or a Dremel cut-off wheel, as needed.

Important Warning: DO NOT file too much off, or you MUST get a new ring set and start over.

Remove the ring, set it aside, and repeat the process for the other rings to be used with that piston in that cylinder.

The expander ring (squiggly one) may not have enough spring tension to hold itself free within the cylinder. It doesn't matter, since its gap has such a large tolerance anyway.

I found it easiest to shorten the expander ring by clipping it with a pair of end nippers.

Note: All of my Nemesis rings were within specs, so none of them needed filing--except for the expander. Yours may differ. See photo below.

Once you have gapped all the rings for one piston, remove it from the cylinder, and install the rings onto the piston in the following order:

• The oil expander ring (the squiggly one) goes in the bottom groove. Both thinnest rings go in the bottom groove, too, with the expander (squiggly one) between them.
• If you're using Omega Pistons, the thick, black ring goes in the middle groove. If you've got pistons from other manufacturers, follow their instructions or the service manual.
• If you're using Omega Pistons, the light tan/gold ring goes in the top groove. If you've got pistons from other manufacturers, follow their instructions or the service manual.

Next, rotate the rings to distribute the ring gaps around the piston perimeter, per the service manual. This will ensure better engine compression, and less gas/oil contamination, for years to come.

Be sure to orient each piston properly, as you prepare to install each one onto a connecting rod. Carefully examine the piston-top. If your pistons are flat-topped, refer to the service manual for directions in orientation. Also, if you are reinstalling your stock (or other) pistons, be sure you get each piston back in the same cylinder it came from.

If you are installing high compression pistons, you will see that the dome is not centered. It is somewhat shifted to one side. The piston side with the most dome should be oriented away from the engine-center--at least it did in the case of my Nemesis pistons. Check with your supplier to get the orientation correct for your pistons, but is probably the same as the Nemesis. See photo below.

Install the right-side wrist-pin retainer into the piston.

Tip: There is a notch in the piston to help you get a small tool in to insert the retainer. Rotate the retainer so that one of the ends is near this notch; it may be easier to get the retainer in.

Safety Warning: It will take significant force to insert the retainer. Sometimes they flip out with great force. Protect your eyes.

Tip: I recommend you always replace the retainers with new ones. It is very cheap insurance against a warped or weakened retainer. The Parts and Tools article in this series has the part numbers.

If you haven’t done this already, place some rags into the crankcase cylinder holes and against the cylinder studs. This precaution is to prevent loosing the other wrist-pin retainer into the crankcase, and to protect the piston. See photo below.

Lube the wrist-pin, the connecting rod bearing, and the wrist-pin bearings of the piston with assembly lube. Then position the piston over the connecting rod. The wrist-pin retainer should be facing to the bike's right-side.

Now slide the wrist-pin through the piston and connecting rod.

Next, install the left-side wrist-pin retainer. Be careful not to scratch the piston skirt. See photo below.

Tip: There is a notch in the piston to help you get a small tool in to insert the retainer. Rotate the retainer so that one of the ends is near this notch; it may be easier to get the retainer in.

Safety Warning: It will take significant force to insert the retainer. Sometimes they flip out with great force. Protect your eyes.

Tip: I recommend you always replace the retainers with new ones. It is very cheap insurance against a warped or weakened retainer. The Parts and Tools article in this series has the part numbers.

Next, remove the rags from around connecting rod for the cylinder you’re going to install.

Insert alignment dowels into the dowel holes in the crankcases, at the base of the cylinder studs. Only do this for the cylinder you're working on.

Tip: Be very careful not to drop a dowel into the engine!

Install a cylinder base gasket. Make certain it is oriented so that all the holes line up.

Tip: Insert wooden blocks under the piston, across the cylinder base to support the piston. I used two, 7 inch lengths of 1"x2" scraps, placed cross-wise. This helped keep the piston from sinking as I worked the cylinder onto it.

Check the chamfer along bottom edge of cylinder sleeve. If it's even a little bit rough, oil-sand it to smooth the inner edge of the sleeve bottom. Finish this process with 400 grit paper.

Clean and re-oil the sleeve bottom after sanding, as needed. Next, check that the piston rings are still distributed properly, then slide the cylinder down over the studs and let it rest squarely on the piston's top ring.

Take picts.

Wiggle the cylinder slightly and carefully over the top ring. Do this at a point furthest from the ring’s gap.

Now, use your fingers or a plastic tool (see the Tip below to see what I made) to compress the ring while gently wriggling the cylinder over the ring. This takes a lot of finger pressure, but you must be careful not to damage any ring. It should not take a lot of downward pressure on the cylinder.

Take your time--even an hour for each ring, if you need to. Just don't scratch, or otherwise damage, a ring. If you do, you'll need to get replacements, and start all over--which is still better than installing damaged rings that may quickly ruin your cylinder and piston.

Tip: I found a couple of plastic, plumbing, faucet wing-nuts in my tool box. I filed a flat onto one of the wings of each nut. I used them sort of like sewing thimbles. They worked pretty well in allowing me to save my fingers, and put more pressure into the ring, as I worked it in, around the cylinder sleeve. See photo below.

Repeat for the other rings. Proceed carefully--especially the thin ones and the oil expander ring (squiggly one).

Important Warning: If a ring gets bent at all or scratched, you must get new rings and start over.

Once all the rings are inside the cylinder, remove the wooden blocks from under the piston. Then push the cylinder all the way down, and over the alignment dowels.

Repeat this entire process for the other piston, rings, and cylinder.

Also see the How to install Hi-Compression pistons in a Roadstar article in this website for more information on installing pistons.

To access related articles, refer back to the Complete Engine Tear Down, Orientation article in this series to see which additional articles best address your situation.

Questions should be asked in our forum (Use discuss link below). The forum is very active and you stand a good chance of getting your questions answered there. If you would like to leave feedback for the author, or have additional information you think will benefit others, please use the comment section at the bottom of this page.

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DISCLAIMER: This information and procedure is provided as a courtesy and is for informational purposes only.  Neither the publishers nor the authors accept any responsibility for the accuracy, applicability, or suitability of this procedure.  You assume all risks associated with the use of this information.  NEITHER THE PUBLISHERs NOR THE AUTHORs SHALL IN ANY EVENT BE LIABLE FOR ANY DIRECT, INDIRECT, PUNITIVE, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, OF ANY NATURE ARISING OUT OF OR IN ANY WAY CONNECTED WITH THE USE OR MISUSE OF THIS INFORMATION OR LACK OF INFORMATION.  Any type of modification or service work on your motorcycle should always be performed by a professional mechanic. If performed incorrectly, this procedure may endanger the safety of you and others on your motorcycle and possibly invalidate your manufacturer’s warranty.

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