Really loud THUNK

[pdrides]

My bike is a '99 wr400 and has been running great. The last couple rides I've been hearing and feeling a really loud thunk. It sounds just like a large rock hitting my skid plate. As a matter of fact thats what I thought it was. What clued me in was that it only seems to happen on a hard landing or harsh bump. It's very random and has only happened a couple times but I want to catch the problem before it gets worse. On quick inspection the only thing I'm seeing is a slightly loose chain but not excessivly so. Anyone have any thoughts? Thanks

[FORMA MOTO]

My bike is a '99 wr400 and has been running great. The last couple rides I've been hearing and feeling a really loud thunk. It sounds just like a large rock hitting my skid plate. As a matter of fact thats what I thought it was. What clued me in was that it only seems to happen on a hard landing or harsh bump. It's very random and has only happened a couple times but I want to catch the problem before it gets worse. On quick inspection the only thing I'm seeing is a slightly loose chain but not excessivly so. Anyone have any thoughts? Thanks

We are going to need more info to help, I think.

Put the bike up on a stand and inspect the steering head, forks, front and rear caliper retainers, swingarm and linkage, and the top bushing for the shock.

Maybe you have loose motor mounts?

[Asgeir]

Could it be that the front forks are bottoming out on a compression stroke ?

Are they or have they been leaking ?

[pdrides]

I'll get it up on a stand and check everything suggested. I tend to think it's not coming from up front, I replaced the fork seals and steering head bearings at the begining of the season and everything seems to be operating fine on that end. I can actually feel the"thunk" telegraph through my feet when it does happen...linkage does sound like a likely suspect. I'll get back. thx

[Grizzalo]

Sounds like something is loose somewhere.