Transmission Oil for 2009 RS 125? | GTAMotorcycle.com

Transmission Oil for 2009 RS 125?

unL33T

Well-known member
Anyone have any idea what oil I should be using in the transmission of my 2009 Aprilia RS 125?

I found some manuals online (bike didn't come with one) and they all recommend 75W90 gear oil. But as far as I'm aware I have a wet clutch so I'd need to make sure whatever 75W90 I find says it's ok for wet clutches. Even the motorcycle-specific 75W90 I can find doesn't say anything about wet clutches. It appears to be for shaft drive bikes for the most part.

Then I found some stuff on forums saying 10W40 motor oil was fine for track use (and they change it every race) but something lighter would be better for street use. The partial bottle the previous owner left me is "Motul TRANSOIL SAE10W30 2 stroke gearbox oil".

Another confusing thing is the manual says to use an oil that meets or exceeds API GL-4 while some forums say anything that says API GL-4 is bad for wet clutches. I think there's just a lot of bad info out there.

The change interval from the manual appears to be once at 1000 km and then every 12000km after that, unless I misread something. So I guess it needs to last awhile.

Thanks for the help.
 
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bitzz

Well-known member
Maybe this will make sense....
We used to run regular 30 non detergent motor oil in our 2T trans (you still can it will be fine) Nothing in the oil but oil. No friction modifiers, no viscosity modifiers. Just pump it out of the ground, strain it through a sock and pour it in the motor.
Then we got SAE GL (GL = Gear lube and is a different engineered oil than a motor oil)
The auto indutry is always experimenting to get better fuel mileage and they came up with a gear lube, low in friction modifiers high in viscosity modifiers, that offered low flow resistance but was VERY viscous (meaning it would pour like water but stick to anything, and stay stuck). So a modern 75/90 gear lube pours like a 10/30 motor oil but sticks to the spinning gears better. Your "Motul TRANSOIL SAE10W30 2 stroke gearbox oil" is SAE 80 gear lube.
SAE GL 1, 2, 3 ratings are mostly obsolete and GL-5 is not recommended for transmissions with yellow metal parts ( your RS125 trans has yellow metal parts) so if you want a SAE rated oil you're using GL-4. GL-4 is recommended for limited slip, read clutched, differentials.
I've run either Klotz or Motul 2T gear lube for years without issue in my Yamahas. Found in the dirt bike section. If you get 12,000km before you need to rebuild your RS125 crank I'll buy you a cake.
 

unL33T

Well-known member
So anything that says it's good for limited slip differentials should be fine? Or any 10W30 motorcycle oil?
 

skip

Well-known member
^ as above I don't have anything else useful to add
 

bitzz

Well-known member
API and SAE GL ratings are automotive... as in cars. The last car with a wet clutch was the original VW Beetle. API and SAE stopped worrying about wet clutches a long time ago.
I suggest you're over thinking this. If you walk into any motorcycle store and buy some 2 stroke dirt bike gear oil you will be fine. If you want to spend more money, buy the expensive stuff. If you have a favourite brand, buy that. If you want to cheap out go to crappy tire and you'll find regular, non-detergent 30 weight oil in the lawn mower section.
I suggest you DO NOT run a modern multigrade automotive motor oil in your transmission, only because it doesn't have enough anti-foam agent and it will spew out the vent. Lubrication wise it would work.
 

spaceboy

Well-known member
My Aprilia also calls for 75w90 but I use Maxima MTLR 80w instead. It's a popular alternative that provides good protection and smooth shifts. It's also cheap at around $11/L.
I'm not one to waste oil but 12000kms seems like a lengthy interval. Maybe read up on what other owners are doing.
 

unL33T

Well-known member
If you get 12,000km before you need to rebuild your RS125 crank I'll buy you a cake.
Well they don't mention THAT in the scheduled maintenance. Piston and rings are to be replaced at 16000 km, though. Although it says to check them at 8k.
 

unL33T

Well-known member
Another user recommended the Honda 80w dirt bike gear oil.

Seems like I might be over thinking it. I just wanted to use something similar to what was recommended but I wasn't sure how to pick a 75w90 that was safe for the wet clutch. Since the interval is so long it's not like I can't just order the recommended one anyway.

I just noticed some trouble finding neutral when I'm stuck in heavy hot traffic for a long time so I thought I'd look into what the PO put in it and if that was correct.

I noticed the AF1 racing site also recommends Motul Gear 300 75W90 so I presume it's safe for wet clutches.
http://www.motul.com/lv/en/products/oils-lubricants/gear-300-75w90
http://www.af1racing.com/store/Scripts/prodView.asp?idProduct=1087

Amsoil responded to an email I sent them and said all their 75W90 oils are wet clutch compatible. They recommended their MTGQT for API GL-4 applications or SVGQT for API GL-5 applications.

Royal Purple recommended their High Performance Marine Gear Lube 80W90 because it does not contain friction modifiers that their Max Gear 75W90 has.
http://www.royalpurpleconsumer.com/products/hpm-high-performance-marine-gear-lube/

Or the Max Cycle Synthetic.
http://www.royalpurpleconsumer.com/products/max-cycle-motorcycle-engine-oil/
 
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unL33T

Well-known member
Ordered some Motul Gear 300 75W90 from Two Wheel in Guelph. Although if they had told me they keep the same stuff but in the 80W90 in stock, I would've just gone with that. I haven't put it in the bike yet as I've discovered I have clutch issues. I made a separate thread about that.
 

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