YZ400 Clutch Disengagement

So I did the search, found somethings that might help, but I still want a little more input.

So about a month ago I was working on my bike, getting it ready to roll, started it up, and rode it around the street. Everything went great, put back in storage, and left it at that. Turns out I never did end up riding. Three weeks later I return, trying to start my bike, takes forever, and runs like crap. Figure its bad gas, I also figure I'll deal with it later.

Finally today, had the afternoon off, decided to go deal with. A buddy and I drained the gas, got new gas in it (with stabil this time might add), and of course, starts up second kick. Gotta love ol' Blue reliability. However, now the clutch will not disengage. (Figured this out actually right before we got it running again, because it would not bump start). Can only start in neutral, and when shifted into first, with clutch pulled in, the bike just stalls out.

Here was my thoughts: my bike is wayyy overdue for an oil change, I know, ridicule me, whatever, I was planning on getting it done this weekend. So is it possible the oil finally gunked up enough to prevent the clutch from disengaging? I know its not the cable, the free play was fine on that. My thought was just change the oil, and let it idle for a couple of minutes, maybe some heat on the plates would free up the action. The local yamaha dealer suggested it might be grooves in my basket, and that's what my search results have suggested as well. However, I find it hard to believe that my clutch would simply STOP all of a sudden, when the last time I rode it I noticed nothing wrong with the clutch operation at all.

My final item of business is to simply crack the case and see whats going on inside, but I ran out of time tonight. What do you guys think? Probably one of those two things? Or is there something else I might be missing? Is there another way of breaking loose the clutch other than just letting the oil warm up for awhile? Like some kind of jerking action?

Sorry if I sound like a tard. I've been riding snowcats and quads my whole life, but this dirtbike thing is relatively new to me. Thanks for the time to read.


I've had to fix this in the past on bikes that sat up for too long. We had to take the clutch cover off and while pulling the clutch at the lever to get some slack, we pried the fiber plates from the steel plates as they were sticking together. I suspect the old oil was the issue.

Another time same issue on different bike was solved by going thru gears with clutch pulled in and holding brake while trying to accelerate in high gears. This broke the bond between the steel and fiber plates and clutch worked well remainder of weekend.

Well I know this is an old thread, and I might get flamed for bringing it up...

But I finally got around to working on my bike this past weekend. Tore open the clutch, basket looked great (no wear at all, just black smudges from where the plates fit amongst the fingers), all the plates looked great, overall I'd say the clutch was in excellent condition considering how old it is. The plates were definately gummed up with BLACK oil though, and took some effort prying them apart.

So I put it all back together, I changed the oil and filter, and let it idle (before it could boil over) and the friggin clutch still wouldn't disengage. The cable is brand new, the clutch is bomb.com, everything should be dialed!

So I went inside cursing. Came back outside 30 minutes later, started it up and let it idle for another couple of minutes... and then I rode off! Works great now! Biggest lesson learned: change the oil more often than I buy my wife flowers! After a new seat install and some brake fluid, I'm ready for spring riding!

Oh and I checked my springs too and they met the tolerances perfectly too. I suspect they might be aftermarket. But I did some research through this whole thing and saw that Tusk makes some heavy duty clutch plates that are supposed to get an increased flyweight effect... anybody have experience with this?

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