300ex cam timing

6 replies to this topic
  • Smacaroni

Posted March 09, 2010 - 06:45 AM


I'm replacing the head/piston on a friend's 300ex - valve took a dump and trashed everything.
But I need to know how to set the cam timing? I couldn't find a manual online, did a forum search no luck. Can anyone shed some light on this?
It's a 2001.


  • Red_Dawn

Posted March 09, 2010 - 09:56 AM


Step 1. Take off the caps on the freewheel side. There should be a middle one and one up to the left side of the cover. Take them out.

Step 2. Take your valve cover off so you can see your cam.

Step 3. Put a socket wrench in the middle screw hole you took out in step 1. There should be a bolt in there and when you turn it, it turns your engine.

Step 4. Turn the wrench and look though the screw hole on the upper left corner. Keep turning it till you see three marks on the freewheel. On the threads of the hole you�re looking though there is a slit in the threads. You want to line the middle mark of the the line that is on the thread of the screw hole you are looking though. It will be tricky to keep it there so get someone to help you hold the socket wrench. When you get the marks there that is Top Dead Center.

Step 5. Look at your cam sprocket. Look at the side that faces on the inside. There should be two marks on the opposite sides of each other. You know that the timing is correct when those two marks are even on the top of your engine (where the valve cover sits on). If those two marks are not even with the top of the engine head that means your timing is off.

Step 6. If your timing is off you will need to loosen your timing chain tensinor (sp) so that you can move the timing chain off the cam sprocket and move the cam so those two marks at even with the engine head. Put the chain back on it. Now look to see if those marks as in step 4 are lined up. If they are tighten your tensior for the cam chain. Check you chain to make sure that it isnt going to come off your cam sprocket or skip teeth.

Step 7. Put your valve cover back on and put the screws back in the the cover. Put your quad back together and and start her up.


  • Smacaroni

Posted March 09, 2010 - 10:05 AM


Step five was the step I needed, thanks so much! I was using the screw driver in the spark plug hole to determine TDC, but #4 will make that easier.

From memory, there's three marks on the outside of the cam sprocket, should the mark with nothing on the opposite side be up? Or doesn't that matter?

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  • Red_Dawn

Posted March 09, 2010 - 10:13 AM


not real sure about that mark

  • Smacaroni

Posted March 09, 2010 - 11:24 AM


well, absolute worst thing that happens when I follow your instructions with only the two marks as my guide is I'm off by 180 degrees, which I can check before I put everything but the rocker cover back on again.
Thanks, you've been a huge help.

  • Red_Dawn

Posted March 09, 2010 - 03:21 PM


here is the link to the website i got the instructions from

  • Smacaroni

Posted March 10, 2010 - 04:32 AM


Pefect, lobes facing down with the lines level with the head.


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