Had the EX out to the dunes and it was acting a little funny at times. Had some clicking that I believe was coming from the clutch. Another reason I believe it may be the clutch is this is my first change to synthetic oil and I've heard some horror stories about synthetic and clutch slipping. It didn't, however, prevent me from winning 5 out of 7 drag races vs. my friend on his 250R. So what are the symptoms?

 

Had the clutch go out on my 250R dirt bike. If it is going out, there will be no question. It will just start slipping and you will be happy just to make it home.
To see how weak/strong it is, put the tranny in 3rd or 4th, rev the motor up some, & see how easy it is to kill the motor by letting the clutch out. I don't mean to peg the throttle & dump the clutch, just get a 'feel' for how much effort it takes on the lever to keep it slipping. Don't slip it for more than a second or two at a time to prevent overheating something. If it requires noticeable pressure on the lever to keep the engine from dying, the clutch facings will go a while yet. As for the clicking...that could be one of several things. What conditions cause it to make this noise?

 

I have been told not to run synthetic oil because it could damage the clutch. This is what a small engine mechanic had told me?

 

Farmr....It would happen mostly in 1st gear I think. I'm thinking it has something to do with the oil. I'm taking it out again Friday and I'll try as you suggest.

 

What makes you think it is the oil?

What makes you think it is the clutch?

The 400EX's clutch is known for chattering when abused. Maybe this is what you experienced. It has nothing to do with the type of oil.

The myths about synthetic affecting clutches are just that, myths. People making assumptions based on speculation.

If you want to feel what a clutch feels like when it is going bad, just pull your clutch lever a little and ride around....