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I have a '90 kdx 200 always spewed oil from vent when jumped. This was 1 of the reasons why I rebuilt the motor and sadly still continues after a rebuild with all seals and gasket replaced and case halfs put together fine. After rebuild I rode around yard and woods with no prob but took it somewhere with some jumps and prob just as bad as before. The oil level is not the problem. I can fill to 1/2 of sight glass it will continue to empty after jumping until I can no longer see oil in sight glass. I have seen other threads where riders had the same prob but no solutions. After I noticed it happened after the rebuild I put a huge gas filter on it backwards hoping it would catch the oil and let the air past then oil flow back to case afterwards but it spews oil threw the air box just as bad. My '00 kx 250 trans case vent looks the same but has a hole at the bottom where it sits inside the case instead of being straight thru like kdx. Could the '00ish kx 250 vent solve prob? Kx spews no oil/atf. Anybody got any other ideas? The only prob with this is it coats the air filter with trans oil. My next move is to run the vent tube thru the air box then back out so it can spew on the ground but hopefully not on the rear tire when climbing a rock. I'd rather figure out how to get the kdx vent to work as it should.

Are you measuring the amount of oil that you are putting in? What type of oil are you using?
You can always just vent the crank case to the ground (I used to send mine through the dog bone at the linkage) instead of into the airbox.

I kinda measure by graduations on the quart bottle. I also use the sight glass with the bike balanced. The amount of oil is not an issue. I use alil less than a quart on the kdx and kx which is what they both call for. I'm saying this from memory but I do pay attention to the amount of oil that's stamped on the case and I do have to use google to convert from .l to .oz. I'm pretty sure you can put a whole quart in either and should be fine. Maybe positive.

It is strange that it happens after your rebuild. Did you replace the crank main seals? My guess would have been that the transmission was being pressurized by the crankcase.

When you jump the bike, you are typically revving the bike harder, right? I wonder if there is a link to temperature and lack of cooling.

Yes replaced all seals. Rebuild was done right, ive done many. Also no sign of seal failure either side while rebuilding. Looks like i could of run the $600 bike a long time w/o rebuild but this prob and spooge caused me to go ahead and rebuild. Both prob still existed after rebuild. New pwk a/s took care of spooge prob but oil outta breather still continues. Another thing i noticed was the parts list for '90 kdx 200 has 2 case breather inserts listed 92005-1210 and 14069(obsolete/pn not listed). Not sure if that has anything to do with it. 14069 looks like a plastic part mine is not. i assume mine is 92005-1210. Im not the 1st owner either so no telling.

That is odd that it is doing that with the correct level (correct viscosity??) Which oil are you running? Have you tried switching oils just for scientific purposes? If you have done a few bottom ends, then you have a tried and trued oil, but just throwing out options.

I looked at the diagram. The part number is for 1990 - 1991 as shown in the little box. The reason the other one won't show up is because it is a 1989 - 1994 picture. If you look on another year.... let's go do that right now..... you will see that the other parts ARE still available and are for the 1989 model.


On a side note, THANK YOU, THANK YOU, THANK YOU!!

I am ever so slowly trying to rebuild a 1987 KX250. The breather hose is obsolete (don't want to ose aftermarket hose, thanks (I know, way too easy). The breather fitting that is for 1989 KDX200 is also for the '87 KX250, which means... that the 1989 KDX200 hose would work on the 1987 KDX200!! Again,THANK YOU!!

(and it is 1.05 meters long, so triple the length of the 1990 KDX hose for less than twice the price) Wrong ID for the 1990+ KDX's, so don't make a run on 'em.

Valvoline MC 4stroke 10w-40 from advanced