[2to4stroke]

I am trying to get a consensus if a clacking sound on my crf during idle is normal or not? It appears to be coming from the top of the engine. I can tell you that the drz 125 i have in the garage does makes a similar but faint sound. It is much louder on the crf. The sound gets quiter when I rev the engine, but at idle it can be heard quite well.

Is it possible the cam chain tensioner is faulty? How could I tell? What else could it be besides the cam chain? The valves are in spec.

The bike is the 06 with about 20 hours.

Thanks for any help...cheers

[_06_crf_250r]

I have a 06 250 and I haven't noticed any noise. This might sound stupid but when I had my 150 I had a noise like you described and it was my heat shield on my header I tightened it up and no noise maybe this is not the same problem you have but I thought I would tell you

[MXCRF1]

If it is idiling very very low it could be the automatic compression release engagin and disenganging. If you turn the idle up do you still hear the noise?

[MXHJosh]

If it is idiling very very low it could be the automatic compression release engagin and disenganging. If you turn the idle up do you still hear the noise?

Thats exactly what it is, my 05 250X does the same thing, it can be quite loud.

[2to4stroke]

So yesterday I had someone start their 06 crf250 and it did not make the same clack, clack. I am hoping it is nothing serious? I am going to recheck the valves. Has anyone else experienced this?

It is heard best during idle speed but can be heard at higher rpms. (just harder to hear)

[124]

It is your decompressor arm not clearing the cam. Take the head cover off and glob a bunch of oil on the decompressor arm pin (the part that protrudes into the cam as it spins).

The decompressor arm is not completely swinging out of the way.

[2to4stroke]

Thank you 124 for the tip! So i lubed the decompressor arm and cam like you suggested. The clacking is still there however. I believe this is the problem area because the sound is the same clack when I turn it over or shut it off. I am now wondering if the spring or arm is faulty? It is annoying loud and makes me nervous having a bike that makes this much engine noise. Can these be removed? Is the purpose so it makes it easy to turn over while kicking it?

[124]

The auto-decompressor system uses an inertia arm to activate the decompressor arm that extends over your exhaust rocker arm. The inertia arm is weighted such that at a certain RPM, it's inertia causes it to swing. (This is the part that is making the clacking noise) Before the arm swings it acts as a very small cam lobe. The decompressor arm wheel hits the make-shift cam lobe and forces the exhaust valves to open slightly. The inertia arm is designed to swing at about 750RPM.

The inertia arm is not functioning correctly. It may be that since you've been running it this way for some time, the part is worn enough that the lube you did is not sufficient.

Did you really, really glob oil all over AND inside where the inertia arm contacts the decomressor wheel? This is critical.

[2to4stroke]

Thanks 124 for the great info, you have been very helpful. I will give it another shot again and take it apart and lube it really good . If that doesn't work then I am assuming the parts are worn and order them. From a visual check it doesn't appear worn. The arm does feel loose in the cam but not sure if that is by design?

[mxrox]

My 07 which has done 5 hrs, makes that noise,so i wouldnt worry about it,my old crf made it also.

[2to4stroke]

I wouldn't wory about except when i heard someone else's 06 and mine was way louder. I think something is malfuctioning because I don't beleive this is 'normal' engine noise. I don't have a lot of confidence when I get on the bike and it sounds like it is going to gernade any minute.

[250bandit]

i have an o4 250 which makes the same noise, especially just before it stalls but open it up a little bit and it smooths out no problem

[howse]

Sounds like mine too. Anyone know the exact part name in order to get a new one? I have an 05, and it didn't start clacking until recently, and it's unnerving.

[124]

I've been reading a lot about people having this clacking sound in their engine. Some 450's some 250's, some have had it since day 1; some developed it later...

I believe the sound you guys are hearing is coming from the decompressor system. In the pics, notice the #3 item on the 250 (bottom pic) and the #4 item on the 450. This is the decompressor weight (or inertia arm). This is what i believe is making the noise.






As you kick your bike over, the RPM's are low enough that this arm does not overcome it's own inertia and stays in contact with the cam (or actuator connected to the exhaust rocker). This actuates the exhaust rocker to slightly depress, releasing compression and allowing an easy kick.

Once the engine fires, the RPM's of the engine increase and is sufficient for the arm to overcome it's inertia. The arm "swings" out of the way of the cam (or part that actuates the exhaust rocker). This process allows for the decompressor system to be basically "disabled".

Now, what I believe is happening to your bikes: The processes are happening as intended (the bikes are running and starting OK) with one problem. The decompressor weight is not clearing the cam feature or exhaust rocker actuator completely. This problem forces the decompressor weight (inertia arm) to forcefully swing back to it's "low-RPM" position causing the "CLACK".

Take the valve cover off and investigate. I'm willing to bet this is the problem (without being there ofcourse to properly diagnose). Take the plug out, and turn the engine over by hand. You should be able to demonstrate the issue by turning the motor over quick enough. I've solved this issue before by applying a liberal amount of lube in the area where the arm meets the cam feature. Some may have wear in the parts needing replacement. Good luck and get in there with some light to really see what's going on...

[howse]

That is definately it. Mine has play in it, I don't know if that it normal, as I didn't check it until it started making noise. Anyone know if it is a problem to leave it, or should I look into replacing the part?