Hey Guys,

Just bought a new leftover 2006 400ex 2 weeks ago. Which I am very happy with by the way.

Have a quick question I cam from riding dirt bikes and now on the ATV. My first dirt bike was at age 16 and was a 91 XR250R. That motor was bulletproof..thats the biggest reason I went with the 400ex..has the XR style air-cooled bulletproof engine on it. Now my XR had an Automatic Cam Chain Tensionor on it so I never had to fool with it. I was just looking at my 400ex and on the Cylinder on the back right side is a diamond kinda shaped thing that is bolted on with 2 bolts and then has a bolt in the middle of it with a Phillips head. First time I have really noticed this and it appears that this is a manual Cam Chain adjuster...is that what this is?

If so I don't have a Service Manual yet so when and how do I make this adjustment? Engine i'd say has around 10hrs on it and I just Adjusted the Valves the other day and changed the oil and filter for the first time. I know it was probably early but I am **** about mantinence.

Any help on this Cam Chain situation would be appreciated.

Thanks,

Matt.

 

Hi MAT400EX06 welcome to the forums. The part you are speaking about is a tensioner which, broke on my brothers '02 400. If you are having problems or notice a noise replace it and replace the chain with a heavy duty chain. The timing chains seem to have a tendency to stretch. Especially after the tensioner spring breaks.

 

Good job on the initial maintenance....you will likely be rewarded with years of trouble tree service. Your engine is fitted with an automatic cam chain tensioner. The bolt in the center pushes against a long spring that operates the chain tensioner mechanism. The only way you could go wrong is install the center bolt before installing the body of the automatic tensioner (thats held by the 2 bolts you speak of). This would extend the tensioner to the full out position and if installed would stretch / break the timing chain causing plenty of grief for you and your engine. Don't go cheap on a Clymer or another off brand manual....get the correct one from your stealership....it will cost more, but will be well worth it. The OE manual is 5X thicker and loaded with information the other guys simply leave out. Welcome to the forums.
Gary

 

<div class="FTQUOTE"><begin quote>Originally posted by: Koopa

Hi MAT400EX06 welcome to the forums. The part you are speaking about is a tensioner which, broke on my brothers '02 400. If you are having problems or notice a noise replace it and replace the chain with a heavy duty chain. The timing chains seem to have a tendency to stretch. Especially after the tensioner spring breaks.</end quote></div>

If the tensioner spring would break this would possibly reduce pressure on the timing chain and the atv could jump time. I have never heard of one of those springs breaking....but I am sure just aboout anything is possible. Normally when something goes wrong with the timing on a 400ex one can point to valves not adjusted properly, timing chain just plain wore out, or the beforementioned issue I posted.

 

garyc66R when we tore down my bro's 400EX. The chain was stretched out and the tensioner spring was broken. I thought it was odd also but as you said anything is possible. Everything is back together and good except we still have a small ticking. I'm pretty sure the valves need adjusted slightly. You mentioned that valves not adjusted properly can cause timing issue's. Can you explain a little more on what happens here?

TIA.

 

Well valves too tight can cause the valves to not completely close....which of course causes power loss and possibly a burnt valve. To loose and power loss happens again because you are not actually the full lobe specs the cam was designed for and beating the heck outta the valve stem. Just make sure you are on top dead center on the power stroke before adjusting. If you are not sure put the spark plug in a couple of threads and slowly turn the engine over with a socket through the access cover on the right side of the machine......you will hear compression hissing / leaking when on the compression stroke. At the top of the compression stroke the hissing will stop and the piston will start going back down....you make have to reverse the rachet and back the engine up a bit to get back to where you need.
Gary