WR426 engine noise..Video inc.

hey guys.

My new 2001 WR 426 is making an engine noise. It isn't a knock. more of a rattle noise.

It has had a rebuild recently (so i was told). So i don't think it could be cam chain or piston slap? Im no mechanic though.

Too me the oil seems really thin. Maybe a little too thin?

It doesn't go away with revs either. If that helps?

How do I tell what the noise is before I pull it down. What should I look for?

If you ignore the first part of the movie, you can hear the noise.


Check your valves!

Could it be valve clearances?

It just doesn't sound like valves. However, I have only ever owned old bikes. These newer bikes are paper thin and may be louder the the oldies.

The bike starts first kick everytime. Could it still be valves?

A valve check never hurt anyone and would rule out most top-end possibilities.

Just sayin'..........

Fair enough. Will do that this week.

I hear there are lots of problems with the valves in these bikes. Does the rattle sound anything like valves?

Well I went to check the valves today. I didn't get that far.

I started to look over it and I noticed the middle bolt on the cam chain adjuster was very loose. Almost fallen out.

Can someone explain what that bolt does?

I tightened it up and the noise went quieter. The noise now sounds a bit muffled and now sounds like the valves are loose.

I have read people leave them loosish so they have play for when they tighten?

Get a manual!!! All questions will be answered and you'll be much happier.

And so will we.......

Quick answer: it's your camchain tensioner bolt. And yes, there is a " looser setting" but there is a proceedure for setting it or you'll break the chain and bend valves. Thatvis also where a manual comes into play.

Nothing abnormal about the valving system needing adjustments on the WR (or ANY HIGH reving 4stroke). They take a lot of abuse when you rev the crap out of them. Keep it under control and you'll all live a happy life.

Pull the clutch cover off and check the primary drive gears on the crank.

My 03 450 has a rattle and after reading a few posts it seems a common problem that the retaining nut comes loose and the gears rattle.So ichecked mine and its tight but the gears are loose on the crank so its obviously been loose at some stage.

My problem now is how much play on the shaft is enough to do damage?

May not be your problem but it's worth checking.

Cheers mate!

Give it a shot.

But my family has a wr250 and a yzf 426 and they are sound the same-ish.

Maybe I'm not use to the noisy yamaha's!

But mine seems a bit louder and faster.

no sound at idle, and then at some aceleration it strts ratling???? my '00 wr400 started that too.... .

if your talking about the bolt inside the cam chain tensioner, benneath the outer one, it is suposer to be loose, and work by the spring itself, although the spring may break ocasionally.... wait, seen the video... sorry, diferent noise, yours is like a knocking, mine is like a ratle/buzz. knocking like that could be a con-rod...

The movie really makes it sound worse. This is like a rattle.

All our yamaha's sound similar. Mines just a bit louder.

1. Clutch basket to clutch gear, rivits working loose OR

2. Buckets loose in the bores in the head. I got a 250 that sounds the same way.

been told that the bike has piston slap. I haven't pulled it down yet because im scared of the price.

If its piston slap. will i have to have the barrel nikasil coated?

Can i just re coat and throw piston and rings in?

am I able to get away without nikasil coating?

Besides for pulling the bike down. What is the best way to know for sure that its slap?

Swifty, Have you pulled the clutch cover off and had a look?

it's not a big job ,You may be surprised.

I just did mine and tightened drive gear nut,took all the rattle out of it.

The noise was worse at idle sounded like it was on the left side but noise was travelling through the crankan reverberating from the flywheel.


Nah haven't pulled it off yet. I kind of wrote that of as it sounds as though it is coming from the top end.

The noise isn't on idle anymore. (since I tightened up the cam chain tensioner)

Now on about mid revs noise rattles pretty bad.

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