YZ 400 coolant leakage


5 replies to this topic
  • caseyinnv

Posted June 23, 2009 - 07:22 PM

#1

Hello all new to the YZ just got it a day ago, no more CR in the garage :worthy: I have coolant coming out of the rad overflow tube shortly after warm-up, rad cap? Also is it normal for it to pop alot on deceleration, it has a white Bros pipe. THX

  • yamaha racing 230

Posted June 24, 2009 - 11:41 AM

#2

if u made sure the rad cap is on tight , do u notice any oil in the coolent ? if not it could be just a worn rad cap thats not holding pressure

  • grayracer513

Posted June 24, 2009 - 01:11 PM

#3

Have the cap tested for holding the correct pressure.

How long, exactly, is "shortly after warm-up"? Your bike will not normally idle for more than a minute at operating temps without blowing coolant out of the overflow, assuming a 50/50 mix of ethylene glycol coolant and water in good condition.

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  • 642MX

Posted June 24, 2009 - 01:20 PM

#4

Hello all new to the YZ just got it a day ago, no more CR in the garage :lol: I have coolant coming out of the rad overflow tube shortly after warm-up, rad cap? Also is it normal for it to pop alot on deceleration, it has a white Bros pipe. THX


YZF's don't like to sit around and idle. Without constant air flow they over heat in just minutes. Also, most riders make the mistake of over filling the radiator. You only need enough coolant to just barely cover the core. If you put in too much, it will spit it back out.

A properly tuned YZF will pop some on decel. If its doing it excessively, you might want to turn the fuel screw out 1/4-1/2 turn. Exhaust leaks also cause a decel pop, so be sure to check the header flange and the slip on clamp.

And welcome to TT. :worthy:

  • caseyinnv

Posted June 24, 2009 - 01:49 PM

#5

Thanks, checking header pipe for leaks, I filled the radiator to the top and let it idle for a while, I was just happy to hear it run after kicking it over for about a half an hour!

  • 642MX

Posted June 24, 2009 - 02:14 PM

#6

Thanks, checking header pipe for leaks, I filled the radiator to the top and let it idle for a while, I was just happy to hear it run after kicking it over for about a half an hour!


Yep, thats too much coolant. Also, if it hasn't had the auto decompression cam installed, you might want to do that. It will make your bike start like a 2 stroke. Look in this thread for 450 DCM: http://www.thumperta...ad.php?t=447989

Keep in mind the just because its a 4 stroke, doesn't mean it won't foul plugs. YZF like to be completely warmed up and rode before shuting them off. I learned this the hard way when I got mine. Starting it up for 30 seconds to let you buddies hear it run will foul them fast.





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