RM80 has water in transmission oil

On my RM80 the transmission oil is getting mixed with water. Is it safe to assume I need to order a head gasket or are there any other ways for water to get in there?

Are you losing coolant from the rads.

well I got the bike in this condition and I dont really want to run it like this.

I seem to have the same issue: trans oil turns milky Grey color after a short time.

my head gasket seems slightly damaged. and i do mysteriously lose coolant.

This could also be caused by the lack of a bottle of bar's leaks, coolant leaks past seals by design. or that is my understanding.

I have had the same issue in the past as well. But mine was from riding in the feilds and getting the motor hot, then going into shallow water. When the water hits the bottom of the engine, or anywhere the is a seal. It then cools the steel too quick and the water gets sucked in. But that was just me, I do not even know if you are riding in water. Hope this helps. :thumbsup:

what about down around the water pump? If the seals around the waterpump go bad can water get into the trans? Also the coolant passage that is behind the water pump cover...does that have any seals that could go bad and cause a leak into the trans?


If you are riding in extremely wet and muddy conditions, it's normal. If you are riding through deep water it's normal. If it's dry out and water ends up in the tranny, it's probably coolant. If you go through some wet spots here and there and theres water getting in, it's a seal.

I got it in this condition so I dont really know what kind of riding it is from.

It could be from sondesation from the bike sitting... that is possible.

another way is thru a bad water pump seal.

I suggest you put new oil in it, run it for a few minutes, ride it around a little, then drain the oil, if it is already milky again, then you probably have a problem. If it looks okay, out the oil back in and ride it for a day, then check again.

Sometimes if it was condesation, you need to flush the crackcase by chanding the oil, running it, then change it again. Hope that helps a little.

I agree, change the oil and make sure coolant is topped up. If you are losing coolant, I would say the most likely cause is through the back of the water pump impellor. I changed the one on my RM250 and it had a large groove worn into it by the seal. The head gasket shouldn't let coolant into the gearbox like it could on a 4 stroke engine because the gearbox is separate.

Hope this is of some help.

Had this problem in a 99 yz125, changed the tranny oil, after a few rides, back to that milky grey. Did some research (YZ manual) states that you shouls change your water pump seal and replace gasket while your at it. This is because its slowly getting behind the seal into the tranny oil.

havent had time to work on it until today so anyway Im back at it. Do I need to pull the clutch cover to get the impeller out? I figure the impeller prolly has a snap ring or somthing holding it in. If this is the case what all is involved in pulling the clutch cover? Do i just undo the cable, pull the kick starter, pull the bolts and the cover will come off?

Yeah dude, take off the whole rightsidecover. Take off your pipe,cable and kickstarter. Should right off. The you have to take the impeller off the water pump and pop in the new seal and gasket. Do not try to do this w/out taking off your rightside crankcase cover because some will get messed up. I forget what it was though. And oh yeah drain your coolant and tran oil before all of this! Pop the new seal in and you should ready to go !.

I ordered 2 seals, from bikebandit.com there diagram showed 2 both. Both are the same diameter but one is thinner. The old one was completely shot so Im not sure how they go on. Do they both go on the outside of the cover?

yah you have to take off the impeller and stuff and you should see both seals. Pry them out but dont scratch the cover.

so a seal goes on each side of the cover?

You need a manual.....

drain oil and radiator, fix water pump seal, fill back up , continue flushing oil after 15min riding until it comes out good.

isn't grey milky oil caused by aluminum clutch plates wearing (normal) and brown chocolate milkshake looking oil from water?

This happened to me when I used to ride *0's on both my 2001 RM 80 and my 2003 RM85.

In both occurrences the oil would turn milky and the coolant level would decrease.

Both times it was caused by the water pump seal leaking (behind the impeller).

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