Jump to content
Sign in to follow this  

piston is hitting valve

Recommended Posts

Hi,

 

I installed a new timing chain on my 2006 YZ250F. I lined up everything correctly, installed the cams so the marks are inline with the head face as the manual explains. Turned the engine by hand and it stopped, as if a valve is contacting the piston.

 

Upon assembly, I noticed that with the | mark on the rotor pointing straight up, the piston was not at TDC. Why is this? Can the rotor be installed more than one way?

I know I have cocked something up somehow but I can't think of what I have done.

 

The rotor looks like it is installed properly, the pickup on the stator lines up with the magnet on the rotor and everything looks good there.

Thank you

 

Share this post


Link to post
Share on other sites

Your timing is 180 degrees off. The timing marks will line up when the piston is at TDC and at the bottom of the stroke. take the timing chain off and turn the motor over until you piston is at TDC. Then you can use the timing marks to set the cam chain

Share this post


Link to post
Share on other sites

Remove the spark plug and drop a long dowl or screwdriver down into the cylinder.

Rotate the engine with the timing chain removed and locate TDC.

Verify that TDC lines correctly with the flywheel mark at that point.  If the flywheel is off, then the Woodruff key slot should be pointing straight up.

While the chain is off, check it for kinks by the drop and pick up method.  You know what to do with it if it kinks up.

BTW, check the crank small sprocket for sharp pointed teeth.  if they are, then its a waste of your time as the crank is worn out.

 

Assuming the crank and chain are good, then just line up the cams again AND set the cam chain tensioner this time as that's why it jumped time when you rotated it.

Good luck.

Edited by ronbuell

Share this post


Link to post
Share on other sites

Fixed it guys thanks for your help. I had installed the rotor incorrectly. I didn't think it was possible but it is. Amazing that it even went on, it did manage to put a small dent on the inside of the rotor though.

Share this post


Link to post
Share on other sites

Your solution is typically what it is. The key does not stay in the keyway and then the flywheel is no longer aligned. Key gets stuck to a magnet.

Good of you to of turned the engine over by hand and were carful to be aware something was amiss. I have seen countless cases where the guy just 'forced it through' and ended up with a bent valve or much worse.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...