second newb question - gear oil vs motor oil

StephanieMitchell789
Edited Date/Time 6/9/2013 10:48am
When I rode 80cc bikes years ago, I was told to use gear oil NOT MOTOR OIL in a two-stroke gear box.

Motor oil, I was told, was for the lower end of a four-stroke, which was designed to handle contaminants caused by combustion that would slip by the pistons and rings. Gear oil, on the other hand, was for gears.

And that's what in a two-stroke's gear box, gears.

But I see a lot of people here recommending motor oil for two-stroke gear boxes.

Please set me straight.
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smeg
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smeg 6/9/2013 7:58am
6/9/2013 7:58am
Use gear oil. Gear oil and Motor oil are not the same..... Designed for different purposes.
ATKpilot99
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ATKpilot99 6/9/2013 8:11am
6/9/2013 8:11am
Many owners manuals spec motor oil for 2 stroke gear boxes and its ok to use as long as you're careful not to get the kind that contain friction modifiers. It's better to use gear oil though.
StephanieMitchell789 6/9/2013 8:26am
6/9/2013 8:26am
Yeah I saw that in my manual, it recommends "Honda GN4 4-stroke oil 10W40" which is why I asked.

But just now I noticed that it also lists Honda HP Trans oil there too. I googled and found that it is 80W gear oil.

What problems do friction modifiers cause? Maybe clutch slippage??

Thanks for the info!
xnationalwrench 6/9/2013 8:26am
6/9/2013 8:26am
ATKpilot99 wrote:
Many owners manuals spec motor oil for 2 stroke gear boxes and its ok to use as long as you're careful not to get the kind...
Many owners manuals spec motor oil for 2 stroke gear boxes and its ok to use as long as you're careful not to get the kind that contain friction modifiers. It's better to use gear oil though.
X2 any motor oil with additives runs the chance of the clutch slipping. gear oil might cost a little more but your bike doesn't use that much

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mx317
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mx317 6/9/2013 8:49am
6/9/2013 8:49am
Motorcycle specific motor oil is fine as it won't hurt clutches.
blusmbl
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blusmbl 6/9/2013 10:07am
6/9/2013 10:07am Edited Date/Time 6/9/2013 10:08am
mx317 wrote:
Motorcycle specific motor oil is fine as it won't hurt clutches.
Correct, as most 4 stroke motorcycles share the same oil between the engine side and trans/clutch side so the oil is designed to be compatible with wet clutches. There are exceptions, some of the Hondas separate the engine/trans, and my Harley (as an example) has 3 separate fill holes. 1 for the engine, 1 for trans, and 1 for the primary/clutch. If the oil has the correct rating you can still use it in all 3 locations.

If Honda recommends it for your bike, you're fine.
downard254
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downard254 6/9/2013 10:12am
6/9/2013 10:12am
Use what the manufacturer recommends.
70sSuperstar
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70sSuperstar 6/9/2013 10:48am
6/9/2013 10:48am
used atf in my two stroke machines for about 40 years

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