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tranny oil in air box....?

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Hello...got a quick question that has me wondering. Today I took the 04 kx250 out for a few hot laps on my track. I noticed that the overflow hose was dripping tranny fluid. Then I noticed tranny fluid in the air box...whats up with that???? Is it possible I have a bad seal or is the tranny oil over full? I just bought this bike last fall, and never had a chance to ride it until now.

Thanks in advance.

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You sure thats not oil from the air filter?

I recently bought a 03 KX250 and the inside of the airbox was a mess from the air filter oil. I can not imagine how tranny oil would get into the airbox. Probably the previous owner did not squeeze enough oil out of the filter and possibly not using a real air filter oil, so it dripped out of the filter?

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My girlfriends 04 KX250 is doing the same thing. We race enduros, she rides in the B250 class and is hard on her clutch. After this weekends enduro, which had alot of very tight trail, we noticed about half the tranny fluid gone. Not a crank seal but the bottom end was super hot from all of the 1st gear tight stuff. We are using ATF Type F. The bottom end got so hot that the oil started foaming and pushed it out of the overflow. I believe that the type F was not made to withstand such extreme heat. She's a very aggresive rider and won her class, so she wasnt just putting around in 1st. We are going to try something else this weekend, Bel Ray or Silkolene.

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Dont know if its the same principal but this happened to me on my KDX220 after i had done a cluth change i filled up with oil as you do but i over filled it and it took a couple of rideouts for it to burn off and sort itself out but my air filter and air box was caked in oil from the overspill never the less i cleaned out the box and filter with a bit of petrol and once the oil level had sorted itself out and wasent spewing into the box everything is know fine again. So it may well have been over filled by the previous owner and as you havent had a chance to ride it untill now you may not have noticed i hope this is helps.

Normski

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I do a lot of tight single track woods riding. I use Shell Rotella T 5W40 synthetic and have never had any issues using that oil in the tranny. It available at Wal-eworld for something like $7-8/qt.

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There is no possible way for trans fluid to enter the air box unless the crankcase vent line is plumbed into the air box instead of the atmosphere. The oil in the bottom of the air box is probably from applying too much to the filter and gravity has pulled it down and off the filter. Or you left the gas on while the bike sat and gravity again pulled fuel into the bowl filling the bottom end of the motor and made the bike run like a dog until it cleared out.

The Type F is not a problem with the bike running too hot. Your girlfriends bike ran hot because she was running it in 1st gear and it will get hot at high RPM's in any gear but the motor is so wound up in 1st she should learn to do the same in 2nd gear. I'm suprised her bike has not locked up the motor ripping it in 1st like that.

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The sections were that tight, thats why she was in 1st alot. After btalking to alot of the riders after the enduro, alot of them mentioned the back to back 1st and 2nd gear tight sections. Im an A rider and I would be in 1st also. We would fry the clutch if trying to ride it in 2nd. Some people run there trans vent lines into the airbox. Especially if there is alot of deep water crossings.

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The sections were that tight, thats why she was in 1st alot. After btalking to alot of the riders after the enduro, alot of them mentioned the back to back 1st and 2nd gear tight sections. Im an A rider and I would be in 1st also. We would fry the clutch if trying to ride it in 2nd. Some people run there trans vent lines into the airbox. Especially if there is alot of deep water crossings.

Sounds like a need for a FWW and 2 more teeth on the rear sprocket then the clutch wouldn't fry. Makes sense on plumbing the vent line to the airbox for water crossings. If that's the case then the trans is being over filled if it's spewing oil into the airbox.

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The bike has an 11oz Steahly and 13/51 gearing. The woods are that tight. Southern NJ is known for its ignorant tight woods. Very dense, tightly packed pines. Bar banging tight.

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I never said that the type F was making the bike run hot, the constant clutching is what does it. The type F does not seem to hold up as well as some other motorcycle specific oils under such extreme conditions. Its very thin and breaks down under severe duty. If your riding on a MX track or more open terrain, it wont be as much of an issue. Ive used it for years with no serious problems, but I have noticed an increase in oil loss during very tough, tight enduros. I believe it expands and foams at a lower temp. than the m/c specific oils. Im also not saying that this is what the original poster is experiencing, its just a suggestion and something that has happened to our bikes.

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Hey thanks fellas, I will drain the crank case oil and refill it with a different oil. I dont know what the heck was or is going on with it, but I dont want to damage the motor. I was wondering if it was possibly over filled by the previous owner...? I do have to say that the bike runs great, tons of power and actually hard to hang onto at times...lol I'm just not used to the two stroke hit......!

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I never said that the type F was making the bike run hot, the constant clutching is what does it. The type F does not seem to hold up as well as some other motorcycle specific oils under such extreme conditions. Its very thin and breaks down under severe duty. If your riding on a MX track or more open terrain, it wont be as much of an issue. Ive used it for years with no serious problems, but I have noticed an increase in oil loss during very tough, tight enduros. I believe it expands and foams at a lower temp. than the m/c specific oils. Im also not saying that this is what the original poster is experiencing, its just a suggestion and something that has happened to our bikes.

Ride on brother! I'm used to wide open spaces and MX tracks.

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It also possible that you had some water in the transmission case ? Water would boil over fairly easy and force fluid from the transmission into the overflow?

I suggest changing the tranny fluid. Please note that the manual says to use regular engine oil 10W40 with API ratings SE,SF,SG, SH or SJ with JASO MA. Higher letters ( like SJ ) mean a better oil. It takes 850ml(0.90qt). The Shell Rotella T has a SM rating with is 3 steps better. It comes in 5W40 which also covers the entire 10W40 range, plus means its a little thinner when the engine oil is cold so the oil can circulate better. Any good synthetic 10W40 will work, I just like the specs on Shell Rotella T Synthetic better :)

I believe(need to research this) that engine oil has lower surface tension(means less likely to foam) and less thermal expansion than ATF.

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