Noisy motor - HELP!

My 2000 WR400 has a noisy motor. It knocks and hammers and it seems to have a lot of internal noise compared to my buddies bikes. The bike performs fine but the engine really has me nervous. I can hear the motor knocking quite clearly over the exhaust pipe (stock pipe). I change the oil religiously after every ride and I checked to see that oil is going to the top of the motor. What could be wrong with this bike. One note, when it was only few weeks old, it really knocked and hammered (louder than this), I took it to my dealer to find out a oil line got plugged with something and wasnt letting oil to the top of the motor. They had to replace the piston, cylinder, crank, rod, bearings etc.. under warranty. I hope I am not having a similar problem because the warranty has long expired. Please help!!

Soulds like there is an oil starvantion problem..

Since it was done under warranty before hand then if there is any other damage ruslting from it you shouldn't have any probs..

Did they do the cams at the same time? also what about mains and counter balancer bearings/drive etc?



**Ride it like you Stole it!**

Matt Porritt

99 YZ400F

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Stick your ear real close to all those hot parts and see if you can't localize the source (like head, bottom end, left side, right side).

My counterbalancer gear was loose on my 426. It didn't hammer but you might say it knocked. Whatever it was it was noisy. It was easy for me to determine that the noise was coming from right case side when I stuck my ear right by the header, but sitting on the bike it just sounded like more valvetrain clatter. Not.

If you have a bad rod bearing (now THAT would make a knock) I would hope you'd have some recourse since on the initial rebuild these were installed/replaced.

Maybe if you scream and wave your arms a lot the shop will see if their old error is causing your new noises. Or maybe being real nice is a better approach. My approach w/ mechanics is not to (if someone is gonna f*** up my bike its gonna be me).

Hope its nothin' serious...

Rode my ol' XR twofiddy with an engine know for almost a year before I sold it. I Couldn't find any problem and I ride the pee pee out it before I sold it would any problems. Hope things turn out fine for you.

A trick we used in the navy to check on leaking steam traps is to place a sold metal pipe against the hot surface. Place your ear up to the other end. The sound will be transmitted through the tube to your ear. It worked great for clanking steam traps, I am not so sure about a clanking engine. But if you are real bored, give it a shot.

Heres something else. I changed the oil today, and the knocking went away for a short time and then it started again. Fresh oil quiet motor, even like a half hour later, starts knocking again. What do yo guys use for oil? Could that be it? I'm lost - what gives!? Its going back to the dealer Tuesday morning.

I would guess that most use Yamalube 4R for their 400/426s. But I would guess that any automotive oil would protect the engine just as well. It may fry the clutch but IMO would not result in any mech. problems w/ motor.

Perhaps earlier oil blockage has lead to pump failure. Nice thick oil is pumped at good pressure, warm thin oil is not and knocking occurs.

Just a guess. I've got my fingers crossed for you & let us know what the problem is (or was).

When does it do it? At idle? Under a load? If it's just an idle knock... a lot of streetbikes will make a light knocking noise at idle that disappears when you pull in the clutch. If it goes away when the clutch is pulled in then you know it's clutch or trans related, if it doesn't change it's something engine related.


MotoGreg - The voice of a new millennium

'99 WR400 - 'cause thumpers rule!

'92 GSXR 7/11 (But I wanna trade it for a dope 916)

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Hmmm, now I am lost! It knocks definitely the most at idle and under load. When you get the rpms up it goes away. I was doing some road running on the weekend with it, and it quiets down when you pull in the clutch. What could be the cause then? Plates, I dont know. It wouldnt surprise me if the plates were worn because of the type of riding I have been doing this season has been a lot of really tight single track, but I still dont understand how this could be my problem. How could it be the clutch if it is knocking even if it is neutral?


Try starting by removing your valve cover and inspecting for loose stuff. If it is just a cam issue you don't want to wait until you lose a chain. Even if it is a rod bearing, it's better to find it before it goes.

I heard that the earlier 400F's (98 like mine) have had problems with the cam drive gear on the crank shaft. Has anyone heard of this problem?

Good Luck


You said " It knocks definitely the most at idle and under load" that doesn't make sense, there is no load when it's sitting idling.

You also said " How could it be the clutch if it is knocking even if it is neutral?" When you are in neutral the power is still going through the clutch assembly, the trans is in neutral, not the clutch. If you are just sitting there idling, no throttle, and you hear the knock then I'd look at the clutch, make sure the big nut for the basket is tight and that there is no play in the basket (no play between the main part of the basket and the big gear riveted to the back of it).

There are so many things that can cause noise and if you aren't familiar with what goes on in there it'll be really hard for you to pin-point it. You may have to wait and see what happens, if it gets worse it'll be easier to find.

I can relate to how people have a hard time with noises because of my customers. I work at a Honda car dealer. The engines made in Japan don't have as strict of tolerances as the ones made in USA, Canada, and Mexico (don't ask me why?) and so most of the time the cars that have a VIN number starting with J will have piston slap, a clatter noise under a light load. Everyone complains about "valve noise" and if they'd just think about how valve noise is all the time and not just under load then they'd understand... but they don't want to think about it, they just want to blame the only thing they know about... Anyway, kinda got off topic there but I just wanted to say that it is really hard to help in this situation without having the bike here in person. Also, you have to get the facts nailed down, is it at idle, under hard acceleration or both or what? I don't want to see you spending money changing everything under the sun trying to track it down...


MotoGreg - The voice of a new millennium

'99 WR400 - 'cause thumpers rule!

'92 GSXR 7/11 (But I wanna trade it for a dope 916)

You can visit my photo album for $1 - ENTER AT YOUR OWN RISK

Sportbike fans, join us at

What I mean is that yes, at idle in knocks. It also knocks at trail speeds when cruising through the trails but not when you are really on it with the rpms up high. When lugging the motor it has a definite knock. I use premuium fuel so it isnt a fuel related knock. I'll have a better idea later today when I take it back to my dealer. Thanks for the advice anyhow.

your little end will knock at tickover & quarter throttle. then it clears at half throttle. just another thought.

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