what oil to use for 1979 RM400?

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Jun 11, 2007
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#1
Im restoring a 1979 Suzuki RM400 and I need to change the transmission oil and the book says 20W40 motor oil. What should I use?.....Bel-Ray Gear Saver?....regular 20w40 motor oil and what brand?
 
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Jun 11, 2007
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#3
Thanks....it says in the Clymer not to use ATF because it could cause premature bearing failure.
 
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#4
Oh well, Im just gonna run some 20W50 Castrol, thats close enough and its so damn hot here in Houston it will be fine.
 
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#5
FYI 20w50 Castrol is not as good as the other products mentioned.
The Spectro and Bel Ray have gear specific polymers and extreme pressure additives as well in their oil to cushion the gear faces and to protect the sliding surfaces of the tranny. They are also clutch friendly, whereas the castrol 20w50 only has to be slippery. The BR and S lubes are roughly comparable in lube weight to 20w40 in their 80w versions and 20w50 in their 85w versions. They are not engine oils. Vintage parts are rare, getting rarer and not any cheaper, so why take chances over a couple of dollars.
OriginalDirt