Loud ticking that goes away once warm

[bluegizmo83]

Hi everyone. I have a 2000 400ex that I recently bought. It had a loud ticking since I bought it, so I tore into it the other day and adjusted all the valves (which were all out of spec by at least double the .004 and .005 spec). After adjusting the valves, it runs and sounds fantastic once it fully warmed up, not even the slightest bit of ticking once it's warm. However, while it's cold, there is a very loud ticking that sounds like it's coming from the right front side of the engine (that is, the right front if your sitting on the quad). As the engine warms up, the tick comes and goes away, untill it's fully warm then it never ticks again. I don't think it's an oil weight issue cause I'm running fresh 10w30 ATV oil and I live in a warm climate (New Mexico). The only thing I can think of is maybe the decompression mechanism is sticking when it's cold or something... Any help would be appreciated.

VIDEO OF TICKING: https://youtu.be/9yktmVVrKLA
Ticking starts to go away and come back around the 1:00 mark in video. It's gone completely by the end of the video.

[bluegizmo83]

Updated original post to add a video link of the ticking.

[OZ-T]

Timing chain guides might be worn or shot.

[bluegizmo83]

Timing chain guides might be worn or shot.

Thanks for the reply. I know a worn or shot timing chain guide could result in chain slap that sounds like ticking, but could that ticking actually go away completely once then engine fully warms up?? I would think a worn out guide would make the noise constantly no matter engine temperature or runtime...

[WwsivicwW]

You're on the right track.. I guarantee that the decompression is the culprit. Once the oil gets hot it will lubricate the decompression mechanism much better and will start working properly. The decompression design on the 400ex is a common issue. Timing chain noise will not go away once the motor is warmed up. A worn out guide will not make any noise.