View Full Version : I put in 900cc of gearbox oil: can I do a few kilometers with that?

05-06-2004, 05:29 AM
Stupid me. Yesterday I had the plastic removed from my '98 RS50 (with '03 AM6 engine), so I decided that I could do a gearbox oil change as well. I had no Internet access to find out how much I had to put in, so I called someone who should know.

That guy told me to put in 900cc of 10W40 motorcycle oil after draining the old oil. And so I did: I removed the oil drainplug, let the oil drain, and in the meantime I went to a nearby gas station to get some oil (Castrol GPZ 10W40 semi-synthetic motorcycle oil), and when returned I put in 900cc.

Now I am reading here that what I *should* have done was to remove the other screw, level the bike, and fill until the oil comes out of the hole.

Now, I have no time today and tomorrow to correct the amount of oil (and the type: I needed 75W oil I read) in the gearbox, but I do need the bike for about 90km of travel (~55 miles)

Is the overfill too critical to do the extra 90km? The bike runs smooth and fine.

05-06-2004, 05:44 AM
Over filling can cause pressure on the crank case seals causing them to blow, for how long it takes i would just check that its no over that limit, as if the seals go it will be even more of a pain in the arse.

Also you want an oil thats not 10w40, more like a 75w light gear box oil.

05-06-2004, 06:27 AM
What exactly causes the extra pressure on the crankcase seals?

Micah / AF1 Racing
05-06-2004, 12:07 PM
We use 700ml/cc in our AM6 motors. The reason pressure can easily rise is the small tranny breather hole cannot overflow fast enough to cope with the rapidly expanding oil as it gets hot.

mike gp-1
05-06-2004, 02:24 PM
Hey Micah, I filled mine till it ran out and then put the level screw back in then I added another 100cc of oil. Does this sound right??

05-07-2004, 03:14 AM
Well, you guys scared the shit out of me, so yesterday I lifted the bike (so it is levelled automatically) and removed the level screw (and fill cap). Although I did put in 900ml initially, not much came out: less than 50ml. And I left the screw open until no more oil flowed out of the hole.

So that would be about 850ml of oil in the gearbox. Isn't that a bit much?

I left the half-synthetic 10W40 motorcycle oil in; the store did not stock 75W90 oil. The viscosities of 75W90 gearbox oil and 10W40 engine oil are not that far apart, and it's still quite cold here in The Netherlands. Also, the bottle said 'super duper blabla protection for wet clutch and gearbox', so I guess it's alright until I visit a better store.

And while I was at it and my girlfriend already angry as hell that I had no time, I also changed the front brake oil and front brake pads. Man, what a difference; I had my rear wheel lifting several times during this mornings home-work trip.

You don't notice the slow drop in braking performance until you renew the parts.

05-07-2004, 07:54 AM
*about to change my gearbox oil
ive got some 75w for mine, i presume theres gonna be 10w40 in there as standard?
if so do i need to flush that out in any way, or just drain and fill? cheers