01 yz 426 leeks oil out the crank case breather hose???

2 replies to this topic
  • ATOWN426

Posted September 27, 2008 - 06:42 PM


I just bought a 01 yz 426 that is super clean and well taken care of. However it spit and popped alot with the choke off. So i took the carb off and cleaned the whole thing jets, needle, floats. So I started it up and seems to be a little bit better but now when its idleing its dumping alot of antifreeze and the crank case vent hose coming out of the head is dumping oil also. Is this normal overheating? I've heard that they overheat fast, but the oil seems to worry me. Any feed back would be greatly apprecaited.

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  • grayracer513

Posted September 28, 2008 - 08:06 AM



First, the coolant:

> You cannot run the engine at idle longer than a full minute without running the risk of boil over. If it happens sooner than that, you may have a problem.

> If you fill the radiator to the top, you WILL push some out as it warms up, because it expands with temperature, and there's nowhere else for it to go.

> The coolant could also be "worn out", the radiator caked with lime, or the head gasket leaking, but it's less likely.

Oil in the breather tube is normal up to a point. It will usually drop some on the ground after a hard run, but if it is drooling just after startup, you may have overfilled the oil system. This is a common newbie error with the YZF's. The bike has a dry sump oiling system (read: http://www.thumperta...131#post5345131 )

When the bike sits, oil migrates down from the tank (frame tube) into the crankcases, making the oil level appear low. If you then add oil to make the dip stick look right before you start the engine, there will not be room for the oil being returned to the tank when the bike starts, and the excess will be dumped back into the top of the head near the breather. To check the oil correctly, start the engine and run for about a minute, shut down, wait 30 seconds, and check the stick.

Also, spend some time looking at the Common Threads sticky in the index. There's a manual download link at the bottom under Miscellaneous, too.

  • ATOWN426

Posted September 28, 2008 - 09:50 AM


Thanks, it does take about 2-3 min. before it starts doing dumping so i suppose its just getting to hot and the oil must have been a little high. Thanks again. I've had two 426 before this and neither one did this so, I was just making sure before something bad happened.

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