[Willwall4204]

Hi, i recently bought a 300ex, In ok condition all it needed was a rebulid. After the rebuild the motor was making a loud rattle noise but still ran fine and was pretty powerful, we were told to adjust the valves. When i went back in and adjusted the valves they were very tight so i set them to .0004 on both sides and put it all back together. Now the rattle is still there but a little worse, and there is a loss in power any ideas on whats wrong??? PLEASE HELP

 

[retro]

You may have adjusted the valves at the top of the exhaust stroke rather than the top of the compression stroke. Take the spark plug out. Watch the valve movements as you rotate the crank (in the normal direction of rotation) to line up the "T" mark. When the intake valve closes you are less than a half turn of the crank from your target, so slow down... and stop turning the crank when the "T" mark lines up. Don't ever turn the crankshaft backwards if you go past the mark. Continue on for two revolutions and try to stop with the T in the window again. Then adjust both valves. Recheck each of them after tightening the locknuts. You can find a copy of the service manual at the top of the manuals section for your bike to use for reference.

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