[THXTom]

Hi All.
Been lurking since we picked up 2 400ex’s last summer. ‘01 & a ’02.
Been long time Jeepers and know our way around them pretty good. New transfer cases, gear and locker swaps, etc.
This season 1 of the 400’s started ticking, pretty loud when first started up, seems to quiet down after it’s run some. Still runs strong thou.
Just doesn’t sound right and it definitely didn’t have this sound last year.
Made a video hopping someone could get us started on what might we go after to repair. Have factory manuals and Clymer book,
Thanks, T
Video:

 

[Here 2 help]

So many possibilities.............

Have you checked the valve clearance? The 400EX has screw tappet adjusters - I have seen the locknut come loose allowing the screw to back out and cause a tick. It could also be a worn cam chain or a stuck cam chain tensioner or a scored piston or a cracked piston or a worn piston pin or or a worn out cylinder (usually caused by running a K&N air filter or no air filter or not properly and regularly servicing the air filter or not regularly and frequently changing the oil) a bad rod bearing or (especially in the case of a "big bore" engine) a cracked sleeve or a chipped tooth in the transmission or an exhaust leak or something else

 

[THXTom]

So many possibilities.............

Have you checked the valve clearance? The 400EX has screw tappet adjusters - I have seen the locknut come loose allowing the screw to back out and cause a tick. It could also be a worn cam chain or a stuck cam chain tensioner or a scored piston or a chipped tooth in the transmission or an exhaust leak or something else

Yes, on both.
When we first got them we went thru each one and checked over the normal maitenance items, new plugs,steering, brakes, electrical, oil & filter change, etc.

Took top off the jugs and adjusted the valve clearance.
Hmm, maybe start there?