Head gasket or total rebuild? PLEASE HELP!


6 replies to this topic
  • Speedz909

Posted October 08, 2013 - 08:57 PM

#1

Background: So i have been riding the last 3 weekends hard at the track. My 07 yz450f was running fine for the last 3 weekends and this past weekend, i recently took the carb out and cleaned it really good because it wouldnt idle for anything. put it back in and it ran like a champ . So this weekend it started smoking white smoke out of the valve cover vent tube. My dad was behind me on his YZ250 and he told me that my bike was smoking like a diesel so i  put it up and ended my weekend early. i have been reading a lot of threads about possible coolant burning from bad head gasket. but today i went to talk to some mechanics from my local moto shop and they told to drain the oil and check if it was milky. i asked them if i should start it and warm it up first or just drop it and look at it, they told me to just drop it and see if it was contaminated. so when i got home just dropped it in a fresh oil pan, i could see some sort of seperation of liquids in the oil not terribly bad but still could see the difference.so i put some new oil in and started it to remove the rest of the oil out of it so it would be ready to replace the head gasket. Well i had it running not even 2 minutes into warming it up if just dies as if someone pushed the kill switch. now it wont start for anything i checked the fluids and the oil just looked the same  with a slight discoloration  of contamination and the coolant which was green-yellow is now blueish in my radiator. so my 2 questions are is it just a bad head gasket and thats why its smoking out of the valve cover vent tube, and did it seize up cause i can still kick it over with ease it just wont start. 

 

 

Please help me i just wanna get back on the track before the snow starts flying!!!!!!!



  • grayracer513

Posted October 09, 2013 - 06:55 AM

#2

You're going to have to tear it down either way.  Pay attention to the torque on the head bolts as you go; one may seem looser than the others, which would be a giveaway. 

 

The smoke your dad saw is a clue.  If it disappeared into the air before it drifted away, and had a kind of odd peppery smell to it, it was steam from the radiator.  That would indicate a head gasket.  If it did not simply vanish into the air as it drifted, and smelled of burned oil, then it was smoke, and you have some kind of problem with the rings and/or valve guide seals. 

 

The only Gen2 450 I've seen with a bad head gasket was severely overheated in order to get that way.  The head dome in between the exhuast valves actually just reached the melt point, and both exhaust seats were distorted.  If you've had heating problems, the gasket is probably involved.



  • Speedz909

Posted October 09, 2013 - 09:16 AM

#3

Hey thank you so much for helping me with this. yes i have been smelling overheating latley but didnt think thay much of it cause i would let it cool before riding again and it had coolant in the radiator. It does have a athena big bore kit on it does that have anything to do with overheating? Is the head messed up and how do i know if it is damaged? so if the head gasket is bad its that why my coolant is blueish now and not yellowish, because oil is getting in the cooling system?

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  • Speedz909

Posted October 10, 2013 - 11:14 AM

#4

You're going to have to tear it down either way. Pay attention to the torque on the head bolts as you go; one may seem looser than the others, which would be a giveaway.

The smoke your dad saw is a clue. If it disappeared into the air before it drifted away, and had a kind of odd peppery smell to it, it was steam from the radiator. That would indicate a head gasket. If it did not simply vanish into the air as it drifted, and smelled of burned oil, then it was smoke, and you have some kind of problem with the rings and/or valve guide seals.

The only Gen2 450 I've seen with a bad head gasket was severely overheated in order to get that way. The head dome in between the exhuast valves actually just reached the melt point, and both exhaust seats were distorted. If you've had heating problems, the gasket is probably involved.

So will i need to get a new head or can mine be repaired?

  • grayracer513

Posted October 10, 2013 - 11:21 AM

#5

That depends on what you find.  The head I mentioned is back on the bike and running fine.  Had to go a little extra deep on refinishing the exhaust seats, but nothing crazy.



  • Speedz909

Posted October 11, 2013 - 03:48 PM

#6

That depends on what you find. The head I mentioned is back on the bike and running fine. Had to go a little extra deep on refinishing the exhaust seats, but nothing crazy.

What am i looking for once i open it up? do i have to break the cam chain in order to get the head off? should i just take everything on the head apart and should i check the valves before i take the head off, will there be a different gap on the valves after taking the the them out of the head?

  • 3d0

Posted October 12, 2013 - 01:19 AM

#7

No, you dont need to break the cam chain, just tie it up with a wire or zip-tie to the frame, don't let it drop in your crankcase.

You can check your valve clearance and write it down somewhere, keep your shims and buckets (valve lifters) organized and the gap will be the same.

I would check for valve leakage first, then check your valve seats and valve faces for any signs of pitting or damage, also check if the valves are bent.

 

Edit: Hope this helps

 

http://www.youtube.c...h?v=c_-n20Op1j0


Edited by 3d0, October 12, 2013 - 01:34 AM.






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