Something is rattling in my motor?

[Stevo]

I have a 2000 400ex and it is making this like rattling in the motor when its idling? What could this be, the valves, timing chain? If it's timing chain how hard are they to replace?

[Grant2k]

i am not familiar with those motors but you probably just have to adjust the chain tension, not replace it. get a service manual and it'll be in there.

[86atc250r]

It could very likely be your timing chain, especially if your engine has a lot of hours on it.

I have personally been thru one stock chain and one HD chain on my 2000 400EX - but it does have a ton of hours, mostly racing.

When the chain is worn out it will make an irregular slapping noise. You will also hear this noise when holding the engine at a constant RPM (usually lower RPMs).

If you've got a constant ticking noise in time with the engine RPMs and have never adjusted your valves, it's likely your valve adjustment.

The engine is equipped with an automatic chain tensioner, so no adjustment is necessary. However, it can only go so far before the chain needs replacement.

Not a big deal to replace - you will need a sideplate gasket. Expect to spend an afternoon, especially if you've never done it before...

[Castor-426ex]

prob the timing chain...changing it really isnt bad it requires you to remove the clutch cover and part of the top end...get a manual and itll be a sinch

I would also advise you to get a new chain tensioner and gasket

while you got it apart freshen up the top end

[hon265mxer]

without lookin at it my opinion would prolly be piston slap if its a rattle, if it was the cam chain, it would be more of a whir that was always there, if it was the valves it would be more of a tick that speeds up when u rev the engine, the piston knock is mostly at idle if u do decide to do ur cam chain instead take a look at the piston while ur in there and measure everything out and make sure there isnt too much clearance

[skemp]

Sounds like a worn timing chain to me, but I suppose it could be piston slap. You might as well replace the chain anyway.

[ridered86]

is it a rattling or a ticking?

id adjust you vlves and go from there.

[Guy400]

Gabe (86atc250r) hit on it pretty well. It's most likely your timing chain but could be a valve adjustment problem if coming from your head area. Here's a slick and inexpensive way to locate exactly where your noise is coming from. Take a push broom and unscrew the handle from the head. Start the quad and while it's running place one end of the broom handle on various parts of the engine and then cup your hand around your ear and the other end of the broom handle. You've just now made yourself a free engine stethoscope. You can hear inside the engine surprisingly well and d@mn near pin-point where the abnormal noise is coming from. You'll hear some clacking from the valves but the noise should be minimal. Listen for the sound you're hearing to be greatly amplified and that'll be your culprit.

Amazing the tricks you learn when you live at the drag strip (for cars):D;)

[ridered86]

Originally posted by Guy400
Here's a slick and inexpensive way to locate exactly where your noise is coming from. Take a push broom and unscrew the handle from the head.

Amazing the tricks you learn when you live at the drag strip (for cars):D;)

maybe on a car when you would need to be 5 ft away. an screw driver works well for me, and you can also pinpoint the spot better to because the tip is smaller. jmo

[Guy400]

The tip size makes little difference unless you're talking about a broom handle versus a 6"x6". All you're doing is transferring the harmonics from the engine to audible noises that get transferred though whatever medium you choose (beit a screwdriver, broom handle, whatever). You hear just as well with the broom handle and you don't have to break your back bending over with a screwdriver:D

[ridered86]

lol you got me there guy400, eitherway its a kick arse trick and everyone shold know it

[Foxnake42]

Ever since I bought mine brand new, when it is cold it sounds like the chain tensioner is adjusting for a few seconds. I thought this was normal? yes...no?????:rolleyes:

Before you go tearing down the motor and getting a 505 stroker check out some of these, and most were either on mine or a friends quad and most all of these were mistaken as an engine noise by someone.

Loose header bolt.

" heat shield

head cover bolt

fuel tank bolt

silencer clamp

skid plate

steering dampner



Just look around for somthing thats not tightened down, and then take the above advise and check out that timing chain and piston etc.

[Stevo]

Alrite cool thx for the replys everyone. Im pretty sure its the timing chain. I'm gonna adjust the valves and see if it gets any better and if not ill have my dad help me tear it down.

Should i just get another stock one or an aftermarket? Whats good?

thx

[Mr_Bub400ex]

id say its prolly ur valves out of adjustment

[Grant2k]

Originally posted by Mr_Bub400ex
id say its prolly ur valves out of adjustment
when my valves are out they tighten and stay open all the time, not the other way around. what does everybody else get? i don't get a tapping, i just get no compression.

[fuddrucker]

I just had the same problem. My engine was making this rattling noise, mostly on deceleration though. I thought it was the timing chain until it started making a loud knocking noise as well. Then I thought it was something more serious.

Turns out it was just the timimg chain. It was so loose that sometimes when you start the motor it would slap around really bad, and other times it would just make a clanking noise. Kind of like valves tapping, but at a higher pitch sound. Once I replaced the chain, the motor ran as good as new and sounded better than when I bought it.

[Mr_Bub400ex]

if my valves get too loose they clack and tick at idle. i cant hear them when the engine warms up or revs. i thought it was piston slap but it stopped when i adjusted the valves. id try adjusting the valves, its easy. better to try it then tear into ur motor and replace the chain to learn ur valves were just a few .001" out.jmo

[86atc250r]

Unlike a 2 stroke engine, piston slap is fairly rare in a 400EX engine, especially one that is stock and hasn't been bored to too great a clearance.

[Mr_Bub400ex]

hey u never know...lol thats what my mechanics teacher said it could be, or the valves. usually piston slap stops when the motor is warmed up so i took it into consideration.

[Castor-426ex]

when you check the chain pull the tensioner as well...you have to pull it anyway...look in your manual and itll tell you how to check the operation of it...then you will truly know if your timing chain is the culprit because if the tensioner is at its most extracted point or near it... then your chain has stretched....or if the tensioner is working at all