Strange grinding noise

So I was riding with my buddy the other day and all was going good until a few hours in. I was coming to a stop, and when I clicked into 1st gear, the bike started making a weird grinding/growling noise.

Obviously, that tells me something is wrong. I don't think it is the rings or anything, since the bike still runs like a champ. If I shut it off, and then restarted it, the grinding was gone. I rode for another hour or so before it came back, and it was right after hitting a pretty hard bump.

That being said, I think it is probably a bearing somewhere in the bike. It still made the growling/grinding noise after I was at a complete stop with the clutch pulled and in first gear. That makes me think I should probably be able to rule out any bearings in the transmission, since the transmission should have been stationary at that point. Long story short, I am wondering if anyone has had this problem before, and what it turned out being if you have. I would be surprised if it is the bearing on the piston, since it only has maybe 8 hours on it. Does anyone else have any ideas which bearing(s) is the most likely one(s) to be shot, or am I just going to be stuck pulling the whole thing apart and just better off replacing them all when I can afford it?

Edit: Forgot to mention, it is a 1995 yz250

Edited by jebova2301

Start with the clutch. They are noisy on yz's from what ive been told (on here) when ive had some strange noises. Thats your cheapest and easiest thing to start with. Pull that and see if theres any issues with the basket or hub. Theres a bearing in there too.

Can you tell which side the noise is on? Did it still shift smooth? Do you clutch when shifting? Is the noise there in neutral with the clutch lever out?

Check the oil, If i go by the check bolt on my 125 it will do this since its to low from factory. change the oil and add the amount stamped on the case and see if it stops.

Yes, the YZ has a noisy clutch because of the straight-cut primary gears.  Sitting in neutral, is there a difference in the noise with the clutch lever puled in vs. out?   That would definitely point toward the clutch but not necessarily an urgent problem unless the noise is REALLY bad.  Several bikes I have show a slight noise difference idling with clutch pulled in or out.  If it's BAD, I'd check the slop/play in the clutch basket.

I probably wont have time to pull the clutch right away, but thank you all for the suggestions.

In order of the replies I got:

I sometimes use the clutch, sometimes don't. In this instance, I had pulled the clutch and was going maybe 10mph as I was coming to a stop when it happened the first time. It happened right when I clicked it down into first. When I shut the bike off and tried starting it up later, it ran fine for a while and i was able to run through all the gears with no problems. I didn't think of letting it run in neutral with the clutch out when it started making the noise. My initial reaction was "ohmanshit" each time and I just mashed the ignition kill button.

Oil was fresh and had just been filled 2 days before I went riding. I think I slipped up and added about 25ml too much oil, but I would really be surprised if that caused an issue.

It wasn't just a noise. You could noticeably feel something grinding. You could feel a vibration that shouldnt be there. I just pulled the clutch apart before riding because it had been sitting a while and the plates were almost stuck together. I pulled them all apart, soaked them in fresh oil, examined the basket and hub for any noticeable wear(there was none that I could see), and then put it all back together including making sure all the plates were installed back in the same exact order they came out.

Again, thank you for all the suggestions. As soon as I have the time to take it apart and look into it further, I will do so. Right now I am really busy with life and finally thought I had got the thing running, but it seems I still have a small issue.

dbart...what part of Illinois are you from?

Edited by jebova2301

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