Camshaft and Crankshaft Parts for Honda GX Engines

A pressure washer sidelined by a leaking crank seal is losing you money over a part that costs less than lunch. This collection covers the bottom end of the Honda GX engines that power most contractor rigs, from oil seals and main bearings to connecting rods and crankcase covers. Not sure which engine family you have? Call 301-519-9274 and read us the numbers off the recoil shroud.

What Lives in the Bottom End of a GX Engine

Below the piston, a GX engine is simple and tough. The crankshaft rides on two ball bearings, one in the block and one in the removable side cover. The camshaft runs off the crank gear and works the valves. The connecting rod ties the piston to the crank, and on the bigger GX340 and GX390 blocks a balancer weight smooths out the shake. Two oil seals, one at the PTO side and one behind the flywheel, keep the splash-lubricated oil where it belongs. There is no oil pump and no filter. That simplicity is why these engines run for thousands of hours, and it is also why the few parts down there deserve real attention when they wear.

Match Parts to Your Engine Family

Honda shares bottom end parts within engine pairs, and the listings here follow the same pattern. GX160 and GX200 engines, the 5.5 and 6.5 HP class, share bearings and seals. GX240 and GX270 share theirs, and GX340 and GX390, the 11 and 13 HP workhorses on most 4 GPM machines, share theirs. Parts do not cross between families, so a GX200 seal will not fit a GX390 no matter how close it looks. The GX340/390 crank seal, for reference, measures 35mm by 52mm by 8mm. When in doubt, go by the engine series stamped on the crankcase, not by horsepower stickers, because OEM equipment builders relabel these engines constantly.

Why Crank Seals Fail More Than Once

A new seal that leaks again in a month was not the problem. Check three things before you press in another one. First, the breather. A pinched or clogged breather tube builds crankcase pressure that pushes oil past any seal you install. Second, the shaft surface. A groove worn where the old seal rode will cut a new lip quickly, and a shaft sleeve is the fix. Third, the install itself. Drive the seal in flush and square, lube the lip with oil before assembly, and keep the garter spring in place. Cheap unbranded seals also fail early, which is why we sell seals that fit right the first time.

Rod Knock Gives You One Warning

Connecting rods in splash-lubricated engines die from low oil, plain and simple. The GX low oil sensor helps but it is not instant, and a machine bouncing on a trailer can slosh past it. Once you hear the knock, shut it down. A rod that lets go takes the crankcase, and sometimes the crank, with it. If you catch it early, a rod, gasket set, and an honest inspection of the crank journal can put the engine back to work for a fraction of replacement cost.

Bottom End Parts by Engine Family

These are order-in parts, so call ahead and we will confirm availability and lead time before you tear the engine down.

From the Field

If the side cover is coming off, do the whole bottom end while you are in there. The cover gasket, both seals, and both bearings together cost less than an hour of your crew's time, and nobody wants to pull that cover twice. Set the cover down cam side up so the tappets do not fall out of position, and line up the timing marks on the cam and crank gears before you torque anything. One more habit that saves engines: check oil before every job, not every week. A GX holds barely a quart, it burns a little as it ages, and splash lubrication has zero reserve when the level drops.

Related Collections

• All Engine Parts
• Honda Parts
• Cylinder Head Components
• Head Gaskets
• Gasket Kits
• Carburetor Components
• Recoil Start Assemblies
• Engine Air Filters
• Pump and Engine Oils
• Visit our Gaithersburg store

Frequently Asked Questions

Which crankshaft oil seal fits a GX390?

The GX340 and GX390 share a 35mm by 52mm by 8mm crankshaft seal. The same seal fits both the PTO side and the flywheel side on these engines.

Why does my GX engine keep leaking at the crank seal?

Repeat leaks usually mean crankcase pressure from a blocked breather tube, a groove worn into the shaft where the seal rides, or a seal damaged going in. Fix the cause first or the third seal will leak like the first two.

Can I replace the PTO side seal without splitting the engine?

Yes. Pull the pump or clutch off the shaft, pry the old seal out carefully, and tap the new one in flush with the lip oiled. Wrap the shaft keyway with tape first so it does not slice the new lip on the way on.

What kills connecting rods in GX engines?

Low oil. These engines splash lubricate from a small sump, so a low level starves the rod journal within minutes. Check oil before every job and shut down at the first hint of knock.

Do GX240 and GX390 engines use the same parts?

Some parts cross and some do not. They share main bearings and the oil drain plug, but seals, rods, and covers are family specific. Call 301-519-9274 with the engine series stamped on your crankcase and we will match the part.