How to Service a Small Engine

In the video above, we service a plate compactor fitted with a Honda GX160. Throughout this guide we use the GX160 as our worked example. Wherever you see a blue callout like the one below, that’s the specific detail for our engine, look up the equivalent spec for yours.

In this video (Honda GX160): Blue callouts like this show the GX160-specific details. Look up the equivalent for your engine model.

⚠️ Safety first: Always work on a cold engine. Disconnect the spark plug lead before doing anything inside the engine. Work in a well-ventilated area when using carby cleaner.

Step 1: Check Your Engine Model and Get the Right Parts

This step is non-negotiable. Spark plug gaps, air filter types, oil capacities, and belt sizes all vary between engine models, and fitting the wrong part is how a quick service turns into an expensive problem.

Find the model and specification number on your engine. It’s stamped or on a label on the engine block, usually on the side facing you when the machine is upright. Take a photo before you head to the parts counter. Most dealers can pull up the exact parts in seconds with that info.

In this video (Honda GX160): The label is on the side of the engine block, formatted something like ‘GX160 UT2’. This tells your dealer exactly which variant you have. Honda parts are widely available.

Parts you’ll need for a standard service:

• Spark plug, correct heat range for your engine (check the manual or the old plug number)
• Engine oil, correct type and quantity per manufacturer spec (see Step 4)
• Air filter, paper, foam, or dual-element depending on your engine
• Carburettor cleaner, aerosol spray
• Replacement drive belt, if your equipment uses one; inspect it while you’re in there

In this video (Honda GX160): Spark plug: NGK BPR6ES or Denso W20EPR-U, gap 0.70–0.80 mm. Air filter: dual-element (outer foam pre-cleaner + inner paper element). Oil capacity: approximately 0.6 litres.

Step 2: Remove the Air Filter Cover and Air Filter

The air filter stops dust, grit, and debris from getting into the cylinder. On equipment like plate compactors that throw up fine particles all day, these filters work hard. A clogged filter starves the engine of air, causes it to run rich, and kills performance.

Remove the cover (usually a wing nut or a couple of bolts) and pull out the filter. Hold a paper element up to the light, if you can’t see through it clearly, it’s due for replacement. Wipe out the filter housing before fitting the new element.

Foam pre-cleaners can often be washed in warm soapy water, dried fully, and lightly re-oiled with clean engine oil before reuse. If they’re torn or crumbling, replace them.

In this video (Honda GX160): The GX160 uses a dual-element filter, outer foam pre-cleaner and inner paper element. Single wing nut on the cover. Remove both elements and inspect each. The foam pre-cleaner is worth washing and re-oiling if it’s in good shape.

Step 3: Remove and Replace the Spark Plug

A worn or fouled plug is behind more hard-starting and rough-running complaints than almost anything else. Replacing it at every service is one of the cheapest things you can do for an engine.

Use the correct spark plug socket and remove the old plug. Read what it’s telling you before you bin it: light tan or grey is healthy; heavy black soot suggests a rich mixture or oil burning; white or blistered points to running hot or lean.

Thread the new plug in by hand first to avoid cross-threading, then tighten firm, but don’t go full gorilla on it. Leave the plug lead disconnected until all other work is done.

In this video (Honda GX160): 5/8″ (16mm) plug socket. Replacement plug: NGK BPR6ES or Denso W20EPR-U. Gap: 0.70–0.80 mm. The plug boot sits on the front of the engine, pull it straight off before using the socket.

Step 4: Drain the Old Oil and Refill with Fresh Oil

Oil degrades under heat and load, picks up contaminants, and loses its protective properties over time. On hard-working equipment, fresh oil is the single most effective thing you can do to extend engine life.

To drain:

1. Place a drain pan under the engine.
2. Remove the drain plug (location varies, check your manual if it’s not obvious).
3. Let it drain fully, give it a few minutes.
4. Refit the drain plug before adding new oil. Sounds obvious. Catches people every time.
5. Alternatively use an oil sucker to remove the old oil (we used this in the video)

Which oil should you use?

Always check your engine manual for the manufacturer’s recommended grade and API rating. As a general guide for most small, air-cooled engines in Australian conditions:

• SAE 10W-30, the most versatile all-rounder; handles temperature variation well
• SAE 30, suitable for consistently warm to hot conditions
• SAE 5W-30, better for cold starts in cooler climates

Fill to the upper mark on the dipstick, not over. Run the engine briefly, shut it off, wait 30 seconds, then recheck and top up if needed.

In this video (Honda GX160): Honda recommends 10W-30 for most conditions. Capacity is approximately 0.6 litres. The GX160 has no oil filter, just drain, refill, and check the dipstick. Drain bolt is on the underside of the engine; 17mm socket. On some compactor frames you may need to tilt the machine slightly for access.

Step 5: Disassemble and Clean the Carburettor

Gummed-up carburettors are behind more small engine problems than almost anything else. Stale fuel, particularly ethanol-blend petrol left sitting in the bowl, leaves a varnish residue that blocks jets and kills idle quality. If your machine has been sitting unused for a month or more, the carby is the first place to look.

Carby clean process (applies to most small engines):

1. Close the fuel tap and disconnect the fuel line from the carby. Have a rag ready.
2. Remove the carby from the engine (usually 2 bolts). Take a photo of the throttle and governor linkages before you unhook them, you’ll thank yourself later.
3. Remove the bowl nut and float bowl. Clean out any fuel residue or varnish from the bowl.
4. Remove the main jet and spray carby cleaner through it until it runs clear. Do not use wire to clear the jet, you’ll enlarge the orifice and the engine will run rich.
5. Spray carby cleaner through all ports and passages until the cleaner runs freely out the other side.
6. Check the float, it should not rattle (fuel inside means replace it) and should sit level when held flat.
7. Reassemble once all passages are clear and the cleaner has evaporated.

If cleaning doesn’t sort it, a full rebuild kit (needle, seat, gaskets) is cheap for most common engines. When it’s well past saving, replacement carbies are surprisingly affordable for popular models. Alternatively, replace the carby entirely. 

In this video (Honda GX160): The GX160 uses a simple slide-type carby, 2 bolts to the engine, one fuel line. Straightforward to work on. Full replacement carbies for the GX160 are readily available and inexpensive if a clean isn’t enough.

Step 6: Refit the Carburettor and Air Filter

Reinstall the carburettor, reconnect the fuel line, and reattach the throttle and choke linkages using your photo as a reference. Getting the governor linkage wrong is easy and results in an engine that won’t throttle properly, the photo step is worth it.

Refit the air filter and cover, making sure the filter seats properly against the housing. Any gap means unfiltered air going straight into the engine, and over time, accelerated wear.

Reconnect the spark plug lead.

Step 7: Check and Replace the Drive Belt (If Applicable)

Not all small engine equipment uses a belt drive, but many do, plate compactors, ride-on mowers, tillers, and others. If yours does, now’s the time to inspect it. Belts that are about to fail tend to do so at the worst possible moment.

Remove the belt cover and inspect for cracking on the inner surface, glazing (shiny, hardened surface), fraying at the edges, or visible slack. Any of those signs means replacement. Fit the new belt per the routing shown on the cover or in the manual, check tension, and refit the cover.

In this video (Honda GX160 plate compactor): The compactor drives its eccentric weight via a V-belt. Belt cover is held by 4–6 bolts on the side of the deck. Check for cracking and glazing, both are signs it’s on the way out. Most compactors use a fixed tensioner, so correct belt length matters. A snapped belt on site means a very expensive doorstop.

Step 8: Wash It Down and Test

A clean machine is easier to inspect, easier to spot leaks on, and a better reflection on how you run your gear. Wipe down the engine, blow out the cooling fins with compressed air if you have it, and give the chassis a wash.

Start it up and run through a quick check:

• Starts without excessive choke or effort
• Idles smoothly, no hunting or stalling
• No smoke from the exhaust (a little on first start as residual cleaner burns off is fine)
• No fuel leaks around the carby or bowl
• Oil level stable after a short run

If everything checks out, you’re done. If it’s still running rough after a full service, check fuel freshness, compression, or get a second set of eyes on it.

Any Questions?

If you’re servicing a different engine and you’re not sure about parts, oil grades, or settings, feel free to reach out to the team at Taman, we’re happy to help point you in the right direction.

Watch the full video above to follow along with each step on the Honda GX160 plate compactor and subscribe for more practical trade guides.

Taman Diamond Tool Solutions – we don’t just supply equipment; we help you understand, care for, and get the most from it.