rattle at idle

I do have a rattle in the engine at idle up to 1600 rpm.
I have dismanteld the engine, got the cams out and head of. Everthing looking fine.
First thing was the squised rubber seal around the cam chain tunnel which was in place and the left overs pushed out!!in the tunnel
Then I noticed in my opinion quite some play in the front cam idler. Since there is no specs about them I was wondering if it's not unusual if the sprocket can have approx 1mm of play if you hold the shaft steady. I do mean axial play.
Could this cause the rattle??? It seemed to have eaten a bit in the side of the tunnel....

Martijn

Not much information to go by, from your post. . .

How many miles on the engine?

Sounds like the cam chain adjustment was overlooked long enough to allow the chain to start whip-sawing inside of the case. I don't think there is supposed to be any free play on an idler pulley shaft. Maybe back and forth just a little, but does the pulley rock on the shaft?

1mm of play sounds really out of spec, but wouldn't cause a rattle as such

Rattle, huh? Does the rattle correspond with engine idle and rpm? Could it be excessive valve clearance?
Can you give a better description of *how* it rattles?

the cam chain is new (300 miles), chain was tensioned according specs. Valve clearance is ok.
The rattle is uneven, not a harmonious sound. Only thing I discoverd was that one idler is running poor, not holding it's speed compared with other ones..
probably the tunnel gasket which was squized out pushed the idler aside??

martijn wrote:

I do have a rattle in the engine at idle up to 1600 rpm.
I have dismanteld the engine, got the cams out and head of. Everthing looking fine.
First thing was the squised rubber seal around the cam chain tunnel which was in place and the left overs pushed out!!in the tunnel
Then I noticed in my opinion quite some play in the front cam idler. Since there is no specs about them I was wondering if it's not unusual if the sprocket can have approx 1mm of play if you hold the shaft steady. I do mean axial play.
Could this cause the rattle??? It seemed to have eaten a bit in the side of the tunnel....

Martijn

If you're seeing wear inside the cam chain tunnel, you probably have located the source of the rattle.

what kind of bike are we talking about?lots of bikes make a little cam chain noise at lower rpms;)

Yes definately, as Wire man just said. You need to get a signature of some sort. We don't have any idea of what bike you are talking about. If the sound you hear is not in a patterned rythm it jst might be the idler. Thats one way to start small

my 650 will get a funny rattle at idle when the carbs are no in snyc,

kzwolfsr wrote:

...We don't have any idea of what bike you are talking about...

For what it's worth, I know martijn from another forum, so I believe he's talking about a 750 twin...

This time it's the Z900 (1200 cc)It made the noise since the last 300 miles since putting the big bore on it.
It's a kz1000 engine in a Z900.and we are dealing withe the front idler.
I was wondering if/when timing the cams if its normal that there is a bit of a slack in the cam chain with the (stock) camchain tensioner tensioned according the manual???What I mean is that the cams not directly respond when turning the crank.
I was thinking of a bit of slack in combination wiht the idler.. still wondering how it can get the side wall

Martijn