Coolant loss, white smoke on start up

7 replies to this topic
  • Brett1981

Posted November 15, 2008 - 02:27 PM


Hello, I would appreciate anyone's past experience with this problem to make sure I am looking for the right thing.
I just bought a YZ426 '02, it runs awesome but coolant was low. I filled it up then when I started it blew white smoke but only on start up, white oil drips out of the breather hose. The dipstick oil is fine though, does this tell me it must only be the head gasket and nothing more? I hope thats all it is!

  • yamaha542

Posted November 15, 2008 - 05:20 PM


blow head gasket

  • redlineblues

Posted November 15, 2008 - 05:59 PM


How long did the bike sit before you bought it? If anything over about 6 months then there can be condensation in the motor. Change the oil.

  • Brett1981

Posted November 15, 2008 - 07:44 PM


I changed the oil and oil filter, the oil and coolant wasn't in good shape and the coolant was very rough so I suppose it won't hurt to change the head gasket anyway, hope they are not expensive. I love working on bikes I just hope this gets it up and running so I can ride it :-)

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  • grayracer513

Posted November 15, 2008 - 09:21 PM


First, differentiate between smoke and steam. Smoke doesn't vanish into the air like steam does. If it was steam, it can really only be a head gasket, or a crack in the head or cylinder (cracks aren't very likely). Oil smoke on startup that does not continue afterward is usually valve guide seals.

I just did the head gasket and a set of rings in one of my 450's for $65 US (TT OEM Parts), so it's not costly at all, really.

  • desert-rat660

Posted November 15, 2008 - 09:30 PM


if u are doing the headgasket only it should take less than 2 hours to do it.

  • usmcpaul

Posted November 16, 2008 - 04:46 PM


FYI, burning coolant will have a very distinct "sweet" smell to it.

  • Brett1981

Posted November 16, 2008 - 08:01 PM


Thanks a lot, I like this forum type thing it helps a lot with the thinking process. I pulled off the head and cylinder, water definitely got in but only in the top end was a good thing to find the problem. One bad thing though, the cylinder has a small crack in the bit that joins the inner cylinder to the outer barrel where the coolant passes on either side up around the barrel and it looks like this is where the gasket started to go bust. Its only a very small volume of metal though (about 1/2 inch x 3/8 inch) so I am hoping its not going to mean I need a new cylinder. I will give the new head gasket a go and I now know what to look for in the head gasket goes again and will know I need a new cylinder if that happens.

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