[blue benjamin]

bmw f650 funduro 1998, so i was checking valve clearance, everything is in spec.

45k km on the clock

i put everything back on correctly as usual, chain tensioner is working properly, plastic guides don't look worn.

now i'm 70% sure it didn't do this noise before, HOWEVER, i wouldn't bet my life on it, maybe i only started paying attention to it now who knows.

so, long story short, in 4th gear, between 70km/h and 90km/h, under acceleration, half throttle, i hear what sounds like the cam chain slapping, it's hard to pin-point and hear the noise properly with the exhaust noise and wind, but that's what it sounds like to me.

when crusing or heavy acceleration it doesn't do it. only when acceleration at about half throttle, and that's for a very brief moment.

SOMETIMES i can also hear it in 3rd gear, but not as much as 4th.

the noise is only for a brief moment, and it don't matter if the engine is cold or hot.


i'm wondering what it could be? is it perhaps normal and not an issue? i'd say the chain isn't worn with only 45k Kilometres on it, and the plastic guides don't seem to be either.

i tested the tensioner, filled it up with oil and it's nice and stiff so the valve on it isn't shot.

should i worry?

 

[Godoh]

Hard to know without hearing the noise. First thing that comes to me is that it may actually be a fuel problem.
The fact that it only happens under heavy acceleration points to possibly pinging caused by low octane fuel.
Next time you fill up put some higher octane fuel in and see if that makes a difference.
Also check the drive chain tension and rollers too.
Pete

 

[blue benjamin]

Hard to know without hearing the noise. First thing that comes to me is that it may actually be a fuel problem.
The fact that it only happens under heavy acceleration points to possibly pinging caused by low octane fuel.
Next time you fill up put some higher octane fuel in and see if that makes a difference.
Also check the drive chain tension and rollers too.
Pete

it-s the other way around, it only does it at about mid throttle ish acceleration


is it possible to check the cam chain tension by taking the valve cover off with the tensioner in?

since the tensioner is hydraulic and actuated by the pressure of oil,

 

[Godoh]

It should be possible to check the tension. Just take the cover off, and turn the engine by hand a few times in the direction it rotates.
You should hear any odd noises if there are any.
Pete

 

[Godoh]

Actually thinking about it, just turn the engine over by hand and use a large screwdriver pressed to the ear as a stethoscope to listen to the cam chain.
Just put the handle end onto the ear, and hold the blade of the driver in different spots on the engine as you turn it by hand. It should be pretty easy to hear any noises that are unusual.
If there are none with the engine off, then start it and do the same thing.
Of course if you have a doctor living nearby who will lend you their stethoscope it may be good but a screwdriver works great too.
Pete

 

[blue benjamin]

Actually thinking about it, just turn the engine over by hand and use a large screwdriver pressed to the ear as a stethoscope to listen to the cam chain.
Just put the handle end onto the ear, and hold the blade of the driver in different spots on the engine as you turn it by hand. It should be pretty easy to hear any noises that are unusual.
If there are none with the engine off, then start it and do the same thing.
Of course if you have a doctor living nearby who will lend you their stethoscope it may be good but a screwdriver works great too.
Pete

Do i need to listen to the chain side? Or would i also hear it from the right side of the engine?

Just a bit hard turning the engine from the right side while listening on the left and ain't really got a helping hand rn

Just got back from a ride, i think i also hear the chain slapping when going over bumps or potholes.

 

[kuyajonathan]

Echo what Godoh said;
Also check the drive chain tension and rollers too.
Pete

Especially when you say going over bumps & potholes

 

[Godoh]

You should be able to put the end of the screwdriver on the top of the tappet cover and listen. It would help if you could listen to the bottom end too, but noises should transfer through the engine case pretty well.

Pete

 

[blue benjamin]

You should be able to put the end of the screwdriver on the top of the tappet cover and listen. It would help if you could listen to the bottom end too, but noises should transfer through the engine case pretty well.

Pete

Thanks guys! I think the issue was the drive chain.

Which really surprised me as the sound sounded like it was coming from inside the engine in the front.

Also surprised it only did it in 4th gear and 3rd sometime.

The upper chain guide that sits on the swingarms was loose and the chain was coming into contact with the metal swingarm.

I will go on a ride tomorrow and make sure the noise is gone. Thanks! Sure glad it wasn't the cam chain!!

 

[Godoh]

I hope that the problem is solved, that is a much easier solution than changing cam chains.
There should be a plastic slider that goes over the swingarm too. Make sure it is in good condition.
Good luck
Pete

 

[blue benjamin]

I hope that the problem is solved, that is a much easier solution than changing cam chains.
There should be a plastic slider that goes over the swingarm too. Make sure it is in good condition.
Good luck
Pete

did the screw driver trick, on both sides, both with the bike off and on, no weird noises.

I will buy a new chain slider and see what happens

 

[Godoh]

It looks like parts of the slider are missing. It is bit tricky but the slider can be put in with the swingarm in place. Just undo the two screws that hold what is left of it place. Clean up where it goes and wiggle the new one in from the front.
You will have to drop the chain off the sprocket to get it in.
Pete