YZ426 (2000/2001) model leaking oil like sieve

Hello Everyone. I'm a trail bike riding bloke from Australia and have a yz426f. I've noticed my ride losing lots of oil lately. I found motor oil dripping from the breather tube on the left hand side of the bike, but on closer inspection, there is oil everywhere around this area. Has anyone seen this and what is the likely cause? I've had to top up my oil a couple of times in the past two weeks now - this is making me nervous, as my mates tell me to keep the oil up on these rigs and make sure you don't run out! :D

I did take the magneto cover off recently, but I'm fairly meticulous when it comes to working on this kind of stuff - I've read that these bikes run a "wet magneto" - I'm going to check it out after work to make sure the cover's on properly. Any other suggestions would be greatly appreciated. Thanks.


If you rev it a lot then some oil will come out of the tube and it will pretty much cover everthing within range; but it's not a large volume of oil. You may see a couple spatters on your boot and a drop or two on the ground, but not a significant amount. If it's really dumpig out then review the way you check your oil level. Remember if the bike has been sitting more than a couple of minutes the you have to start it and run it for a couple of minutes BEFORE checking the oil. Otherwise it will look empty when it's actually full. I hope this helps.

As a test, I would loosen the main carriage bolt near the top of the cylinder while the bike is running to see if you are getting the proper oil flow to the motor.

There could be an obstruction with the filter or something else that is pushing it back out the breather.

Simple test, should only take a minute....

I am having the smae problem but the only time I notice it is when I get home from a long ride and in the bed of my truch there is oil from where it has came out of the breather tube. It does not leak at all when sitting in the garage just after a long ride.

Also did not get to ride last weekend and was messing around with thebike and I check the oil (without running it) and it was not even on the dipstick. So I filled it and filled it until it was at the proper level. Well needless to say I way overfilled it. Is there a way to get some of that out or should I just drain it all and start all over again? Thanks

I would just drain it all and start fresh.

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