2003 Yamaha YZ450 weird noise - chain slap?

I have a 2003 YZF450 and need help. I was riding over the weekend and my 450 was running fine until I landed from a jump and it made a horrible clanking sound. I pulled in the clutch and came to a stop and the noise went away. The bike runs fine and goes through the gears but when slowing for a corner or shutting off the gas it makes alot of noise. It sounds like it is coming from the front sprocket or transmission. It sounds worse than chain slap but I am not sure. Has anyone else had this problem?


1) Did it make the noise before you landed that jump?

2) Does it make the same noise in all gears, or only one?

3) If the noise changes in frequency or otherwise, does it change with bike speed, or with engine speed? In other words, does it sound louder or faster as you go faster, regardless of what gear you're in, or does it sound louder or faster in 1st than in 2nd?

Check 3rd gear I have seen a few go like this....I hope that is not the case. Is the chain real loose or normal?

you are missing teeth on a gear prob. 3rd

How worn is your chain? Is it striking the sub-frame? You can look at the inner side of the sub-frame near the chain and see if it's been rubbing on it. I find if my chain is just slightly loose I'll get the clacking sound of the chain trying to grind my sub-frame to nothing. A little chain adjustment and lube and it's gone, no more noise. I would suggest checking this first and seeing if an adjustment fixes the problem before tearing into the cases.

I have a similar or maybe the same problem. I started to hear a noise about a week ago but thought I was hearing things since these bikes make all kinds of noises anyway. However, today I went riding and the noise got noticeably worse, especially in third gear. Under acceleration in third gear, it almost sounds like a hammer is floating around on the right side of the bike. The other gears dont sound anything like third. So, am I correct to assume third gear is missing teeth as said in the thread or something else? thanks

Oh, by the way, same bike, 2003 yz450.

I bet it is your chain slapping. All my YZ's have had this problem and you usually don't notice it right away. Anyone have another solution besides just tightening the chain?

I do here the chain but that has always been there. This sound is getting worse and coming from the right side. The thing that bothers me is that it is very bad in third gear and almost non-existent in all other gears at all rpm's. It became so noticeable yesterday I got scared so i shut it off. This type of thing is beyond me mechanically so I am going to take it in to a dealer, but didn't want to go in blind.

I was actually the one that started this thread. My friend posted the original for me, since I was not a member back then. I have split my cases and found out that 3rd gear was missing a tooth. Waiting on the parts to put it back together as I write this.

The way I finally diagnosed it, was to go down the driveway in 3rd and let off the gas. It would slightly clunk and make a chain slap type of noise. I tried the same thing in the other gears and they were smooth and quiet. I knew something was wrong in the beginning, but it was hard to narrow down when I was on a motocross track. It would always accelerate smoothly and shift fine, it was only when the throttle was chopped in 3rd that it would make these noises.

Hope this helps.

P.S. Make sure you replace the matching pinion gear also.

I hear the same noise in low second. But I'm pretty sure the chain is just slapping for me because I'm really low in rpm. I should probably split the cases and see just to make sure.

Thanks for the input. I took it to a dealer that I trust (I think) and he told me that's a common problem in that transmission (especially third since thats what most people ride a majority of the time, I do since I ride a track). He rode it and when he went by in third he was nodding his head (I couldnt believe how loud it was without helmet as a bystander). But here's the thing, he said it would be at least 10 hours labor to tear apart and put back together, plus parts. At $80/hour, are kiddin me?? Well, I loaded it back on my truck and now realized I need to become mechanically inclined in a hurry!

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