Zongshen RX3: Oil Lubrication System Maintenance
 

The NC250 engine employs two oil pumps for lubrication. Oil flows throughout the engine as shown in the diagrams below.

http://i442.photobucket.com/albums/q...pstokp60cy.jpg

http://californiascooterco.com/blog/...LubeSystem.jpg

The Zongshen oil system has two oil reservoirs. One 'reservoir' is the oil sump, or crankcase, where all the oil collects after lubricating the crankshaft, piston, and the top end of the engine. The other reservoir is the 'gearbox,' which contains the sight glass, and is located behind the clutch cover.

The following diagram shows the location of the oil drain plugs and oil fill plugs.

http://i442.photobucket.com/albums/q...ps7mxv5ogd.jpg

The photograph below shows the areas drained by the several drain plugs.

http://i442.photobucket.com/albums/q...psbsl2fhtz.jpg

Inside the orange circle is the (gearbox) drain plug for the left oil screen. The location of this plug on the side of the gearbox allows you to drain most of the gearbox oil with the least mess. Inside the green circle is the hole for the magnetic drain plug. This drain plug is located directly beneath the transmission, and is ideally located to collect fine metal contaminants shed by the gears. It is separated by a low, vertical baffle which helps to keep metal contaminants near the magnet. Remove the magnetic plug to drain the remaining oil from the gearbox.

The left oil pump draws oil from the crankcase sump via the oil screen port located inside the blue circle. The oil screen traverses the engine from this port, and the drain plug for this oil screen is located on the right side of the engine. This oil plug drains the crankcase sump of the engine.

The oil filter chamber is located inside the black oval. The oil filter traverses the engine, and the oil filter cap is located on the right side of the engine. Removing the oil filter cap drains the oil from this chamber and the oil journals which lubricate the crankshaft, piston, and cylinder head.

The purple circle shows the oil journal which travels through the crankshaft. The crankshaft is fed oil from an oil journal located inside the right crankcase cover. This oil journal lubricates the contact area between the crankshaft and the connecting rod. The red circle shows oil ports in the upper connecting rod which lubricate the piston pin.

It is important to inspect the oil seal in the right crankcase cover which forms the seal with the end of the crankshaft. If this seal is damaged it must be replaced, since it maintains oil pressure for this important lubrication passage.

http://i442.photobucket.com/albums/q...pszjpw9ocq.jpg

Proper Method of Checking the Engine Oil Level

Because the upper (gearbox) oil reservoir is fed by the left oil pump, the oil level in both reservoirs changes under different operating conditions. Therefore, you must follow a specific procedure to properly determine the actual oil level in the upper (gearbox) reservoir.

Check the oil level when the engine is warm, after it has reached operating temperature. Let the bike idle for a minute or two on the kick stand, in an upright position. Then turn off the engine, and wait a minute or two for the oil to drain. Finally, balance the bike in a vertical position, and observe the engine oil level in the viewport. If the engine has the right amount of oil, the level will be between the upper and lower scribe lines, as shown in the photo below.

http://californiascooterco.com/blog/...1_4721-650.jpg

If you fill the RX3 with the specified, 1.7 quarts of motor oil at each oil change, you will have the proper amount of oil in the crankcase. You can verify the engine is not burning oil, or leaking oil, by checking the oil level in the manner described above.

Oil Pumps

The right oil pump is located behind the right crankcase cover, behind the clutch basket. The right oil pump is driven by two plastic gears which connect to the small gear on the base of the clutch basket. The right oil pump is shown inside the red circle in the photograph below.

http://i442.photobucket.com/albums/q...pslt9izazl.jpg

This oil pump has a pressure relief valve which prevents damage to the pump and the lubrication system.

http://i442.photobucket.com/albums/q...pswvb6gejz.jpg

The left oil pump is located behind the left crankcase cover, behind the flywheel.

http://i442.photobucket.com/albums/q...psbiqhka2s.jpg

The two oil pumps are driven by a single shaft which travels across the transverse axis of the engine.

http://i442.photobucket.com/albums/q...pstlyyeyn9.jpg

http://i442.photobucket.com/albums/q...pswtu7qb3d.jpg

Whenever you remove either the clutch basket or the flywheel, it is important to remove the cover of the oil pump, and inspect all components of the oil pump. If a rotor in either oil pump is worn, replace both rotors in that pump. The rotors wear together as a matched pair, and both rotors should be replaced at the same time.

Oil is the lifeblood of an engine. If either oil pumps fails, engine damage is likely to occur.

Important Lubrication Passages

It is also important to maintain the oil passages in the engine. Damaged oil seals must be replaced, and oil journals must be kept clean and unobstructed.

A vital oil passage connects from the bottom of the right crankcase to the right crankcase cover. When removing the right crankcase cover, it is important to verify this oil passage is free from obstructions. After entering the right crankcase cover, this oil passage connects to the end of the crankshaft, lubricating both the crankshaft and the connecting rod. It is important to inspect the oil seal in the right crankcase cover which forms the seal with the end of the crankshaft. If this seal is damaged it must be replaced, since it maintains oil pressure for this important lubrication passage.

http://i442.photobucket.com/albums/q...pszjpw9ocq.jpg

When servicing the clutch, verify the oil holes in the push rod cap are unobstructed. These holes lubricate the clutch discs.

http://i442.photobucket.com/albums/q...pstneibpnp.jpg

http://i442.photobucket.com/albums/q...ps3zpc4xtm.jpg

Important Lubrication Passages in the Top End of the Engine

When servicing the top end of the engine, it is also vital to keep the oil passages feeding the cylinder head clean from obstructions.

When removing the rocker cover from the cylinder head, it is not necessary to remove the two screws that lock the rocker pins, unless you need to replace either the rockers, or the rocker pins. If you do remove the rocker pins, always verify their correct orientation, or the oil lubrication passages will be in the wrong position. Improper orientation of the rocker pins will starve the cylinder head of oil, and damage the engine.

http://i442.photobucket.com/albums/q...psqpvt8ujn.jpg

http://i442.photobucket.com/albums/q...ps4snduaqd.jpg

When the rocker cover is removed, verify the oil journal on both sides of the cylinder head is unobstructed. The oil journal is inside the red circles in the photographs below.

http://i442.photobucket.com/albums/q...psatcfumly.jpg

http://i442.photobucket.com/albums/q...pskoswn1bo.jpg

When the cylinder head is removed, verify the oil journal on both sides of the cylinder is unobstructed.

http://i442.photobucket.com/albums/q...ps7opblmor.jpg

http://i442.photobucket.com/albums/q...ps3oimndi6.jpg

Also, when removing the cylinder, locate the oil jet which lubricates the bottom of the piston. The jet is located inside the red circle in the photograph below. Verify this jet is unobstructed.

http://i442.photobucket.com/albums/q...pshtiaonwr.jpg

Also make sure the oil passage in the crankcase which feeds the cylinder head is unobstructed. This oil passage is located inside the orange circles shown in both photographs.

http://i442.photobucket.com/albums/q...psmodrrmbk.jpg

Wowzers Spud , What a great post and pictoral tutorial. I'm kinda glad your holed up for the winter and finding time to dig all these RX3 related knowledge tidbits for us. Thanks, rj

You're welcome. Thanks for the kind words, Rob. :)

Yes, I ride all I can during the summer, and do research during the winter. ;)

Wow!, I think I understand how it works, why you need to follow that procedure when you check oil level, and why it is important to drain all four orifices when you change oil.:clap:
CSC is offering a "quick oil change" kit. I'm guessing that it gets installed in place of the magnetic plug; is this right? How much of the 1.7 quarts will drain out the magnetic plug hole if you haven't opened any of the others?
Thanks,
Dan

That's great. :tup: I'm glad I could help. :)

No, I think the oil change kit includes oil, an oil filter, an oil pan, a funnel, and a socket wrench. ;) I wouldn't replace the magnetic drain plug, anyway. ;)

If you open it first, most of the used oil will drain out the magnetic, drain plug opening. I would estimate the quantity at over a quart of oil.

I recommend opening the left, oil screen plug first. You will make less of a mess, since you can open the plug partially, and the draining oil won't hit your hand. ;)

Here is a video which describes how a trochoidal (gear) pump works.

https://www.youtube.com/watch?v=e1lcKe-eD0k

Pretty awesome


:thanks: