New owner of a 07 KLX250S with 4k miles. During a ride around the hood earlier tonight I noticed a noise that sounded a bit odd. It's a kind of rattle or light knock when the bike is under hard acceleration. I've experienced ping/detonation on several bikes but this doesn't sound the same. The engine almost sounds like a diesel when the noise occurs.

Bike is mostly stock. It has a K&N air filter, stock carb & exhaust. As far as I know a jet kit wasn't installed.

What could the noise be if not ping?

 

Cam chain maybe, valves need adjusting? Hard to diagnose a noise from a typed description

 

I'll try to grab a video to capture the audio. I can't reproduce it while its sitting on a stand.

 

Could it be the chain hitting the upper roller?
If you weigh enough and the chain is loose enough, you can engage the chain roller easily.

 

Mine makes a knocking or rattling noise under low RPM load, turns out my rear wheel mud deflector (not sure what it's called) was vibrating and rattling on the swingarm under engine load.

 

Perhaps Chain slap. Does it do it when you are going slow and try to accelerate?

 

Yes, though I can reproduce it in pretty much any gear when rolling on the throttle at a lower RPM. The engine sounds tight at idle. There is a little valve tappet noise but that is separate from the diesel-sounding noise I'm hearing.

 

When my cam chain really started to clatter, I likened it to rocks shaken in a metal coffee tin.

 

Here's the noise.. hopefully it came through clearly on the gopro

 

Nothing has changed on the bike since the sound started?
Did you just install/reinstall a skid plate?
Sounds like my skid plate without and double sided foam tape stuck between the frame and plate.