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Transmission Servicing

The Suzuki RL250 Owner's Manual recommends changing the transmission oil every three months using a 30W motor oil. You can certainly use the 30W motor oil as Suzuki recommended 40 years ago or you can use a modern motorcycle transmission oil. The new oils are available at your local motorcycle shop. They are designed to be use with wet clutches and are excellent lubricants. I use the Bel-Ray 80W Transmission Oil which is about equivalent to a 30W motor oil and change it once a season. This is not the thick hypoid oil or grease that is used in a final gear drive system.

To change the oil, first start and warm the engine. Support the bike on a stand ensuring that it is as level as possible. Remove the black rubber oil filler plug just above the kick crank. Remove the drain plug from beneath the engine with a 21mm wrench or socket. Allow the oil to drain into a suitable container. Dispose of the used oil properly.

There are actually two plugs on the bottom of the engine with the same size hex head. The bash plate was designed to allow access only to the drain plug. The plug that is not the oil drain plug contains a spring and plunger that is part of the shifter mechanism. Removing this plug should be avoided. It is, however, easy to tell them apart. The drain plug hex head is parallel to the ground and the plunger plug head is at angle to the ground. Again, with the original bash plate hole there should not be a problem but, if the bash plate has been 'modified', you might have access to both plugs.

After the oil has drained, replace the drain plug and tighten. About here the technical writer will say something like, "Reinstall the drain plug using a new gasket". In the real world we don't always use a new gasket, though. Fortunately, the gasket on the drain plug (and the plunger plug) are of an aluminum crush design and will last through a few oil changes. Do yourself a favor and look it over before reinstalling. If it is cracked, it will leak.

While you are inspecting the gasket for condition you might wonder why it looks so much like a spark plug gasket. That's because it is a spark plug gasket. So, you might plan ahead and save a couple of the gaskets from your old spark plugs to use when the drain plug gasket needs to be replaced.

With the drain plug in and tightened you are ready to fill with new oil.

The 1974 RL250 Owner's Manual gave 700cc (1.5 US pint) as the transmission oil quantity. The 1975 manual gave 850cc (1.8 US pint) as the correct quantity. This is an interesting issue as the volume within the engine that contains the oil did not change from year to year.

The recommended quantity of oil to service the transmission is cast into the clutch cover just above the kick starter crank. A true 1974 RL250L clutch cover will have 700cc cast in to it. The 1975 RL250M will have 850cc. Both versions of the clutch cover will fit the 1972-75 TS250 and the 1973 TM250 (later TM cases were black) in addition to the 1974/75 RL250. Since the 850cc version is a direct replacement, it is up to the owner to decide what to do.

A tip to use in the field, or one that can work all the time, is to remove the 6mm hex head bolt just forward of the kick crank before filling the transmission with oil. Add oil until it runs out of the hole, reinstall the bolt, and you are good to go with the correct quantity. Oh yeah...."Reinstall the bolt using a new gasket". Interestingly, the location of this bolt appears to be in the same location of both the 700cc and the 850cc covers.

Check out the Magnetic Drain Plug in the Products section.

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Copyright 2014 Matrix Motor Sport
Last modified: 05/26/14