2000 XR4 blowing oil out of the breather

hey guys, i just put my motor back together, i had to tear if apart to fix a broken tranny, before i tore it down i hadnt noticed any oil being blown out if the breather tube, but after i put it back together and went and rode last weekend i noticed oil coming from the upper breather tube and lower tube. im loosing so much that when i started riding had it half way up the dipstick and when i finished the stick was dry. any ideas why its blowing out so bad? thanks for any help

If yo had the top end apart you may have broken a ring. Did you do a compression check?

Are you sure you are using the proper method for checking the oil? Oil coming from the crankcase breather tube could be a sign of an overfull crankcase. If you are not sure of the proper method do a search here and it will turn up lots of results.

You are supposed to hone the cyl when tearing the bike apart. This helps the rings to seal up again. You are loosing oil so fast it might as well be a broken ring. I would throw in a new set just to be sure. (but check everything easy first).

My XR400 didn't blow oil even at WOT. It burned it until the chamber junk lifted the valves off the seats and it wouldn't start from low compression.

Last year, I rebuilt a 83 FT500 (like XL500). It blew oil like crazy with the new Wiseco piston. I believe I had the cam timing off. On old bikes, sometimes you need to slot the cam sprocket and use a degree wheel to set it. So, changes in the cam chain tension really affect the timing.

That all the errors I can think of for such an immediate change. There are lots of opportunities for "learning" with part time mechanics.


If you put more than 2 qts in it, no matter what the dipstick says, you over filled it. In that case, it being blown out the vent line is typical.

As stated, you must check the level a specific way or you'll get a wrong reading.

i agree with Rockjockey and TR42...drain the oil (change the filter) ....put in 2quarts and try again.

thanks a lot for the info guys, ill drain the oil tonight and im going for a ride tomorrow and i will let yall know. thanks matt

It is hard to believe that a guy who could rebuild an entire engine from the tranny up would have trouble with oil level?

But--always do the easy things first. Ya never know.


hey guys thanks for the help, went and rode on sat still had a little blowing out but not as bad as before. guess im gonna pull the cylinder off and put some new rings in it. thanks again! matt

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