yz400f decompression lever not working


4 replies to this topic
  • ramcharger

Posted September 10, 2015 - 09:52 AM

#1

Hey would anyone know why my bike is hard to kick over when the spark plug is out and even when i use the decompression lever it doesnt help. The decompression lever is hookep up and does push the valve down but its still just as hard to kick over. The bike has been sitting for a few months too and just was rebuilt. Could the timing be off causing this or what?



  • grayracer513

Posted September 10, 2015 - 01:13 PM

#2

If the plug is out, the decomp lever does nothing simply because there is no compression to release. 

 

If the engine is overall hard to turn at any random point in the rotation, something is binding, and you have to locate the problem and correct it.  If it turns freely until it gets to a certain spot, the cam timing is probably wrong, and causing on set of valves to impact the piston.  If that is the case, you have probably bent both or all three of the affected valves.



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  • ramcharger

Posted September 10, 2015 - 03:00 PM

#3

If the plug is out, the decomp lever does nothing simply because there is no compression to release. 

 

If the engine is overall hard to turn at any random point in the rotation, something is binding, and you have to locate the problem and correct it.  If it turns freely until it gets to a certain spot, the cam timing is probably wrong, and causing on set of valves to impact the piston.  If that is the case, you have probably bent both or all three of the affected valves.

is the only way to check for bent valves is by taking them out or can you take the cams off and see?



  • fishtime9

Posted September 13, 2015 - 07:47 PM

#4

You can check them by doing the liquid test! That's one of the techniques i used on my 4 wheeler.

Take the head off and spray "carburetor cleaner" down the exhaust and intake enter/exits, then turn it upside down and see if any liquid escapes from the valve ends on the opposite side. (Youtube is your friend, "Liquid Valve Test").



  • ramcharger

Posted September 14, 2015 - 10:44 AM

#5

You can check them by doing the liquid test! That's one of the techniques i used on my 4 wheeler.

Take the head off and spray "carburetor cleaner" down the exhaust and intake enter/exits, then turn it upside down and see if any liquid escapes from the valve ends on the opposite side. (Youtube is your friend, "Liquid Valve Test").

ok thanks







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