Clattering noise on trailing throttle

[foxcorner]

Originally Posted by cheefkeef

I had a think about your question re: how to tell if its the cam chain or the drive chain and I have a suggestion that might work.

The trick is to come up with a way to seperate the two systems and isolate the noise as being caused by one or the other. Fortunately we have a gear box fitted with a neutral gear and a clutch that can do this.

I would try getting the bike going and then pulling the clutch and letting the engine revs drop, listen if the clattering noise suddenly changes with engine speed, or whether it seems more linked to road speed.

Alternately you could try listening to the engine whilst stationary and in neutral gear. Increase and decrease engine speed and see if the clattering noise is present without the drive chain rotating.

Good luck, Keef

Yep - these are exactly the tests I intend to do... once the temperature rises.

Actually, I was going to go one step further: find an empty road (plenty round here) and do this: get to 45-50 mph, pull in the clutch, drop the revs, kill the engine and listen while coasting to a stop.

From earlier tests somewhat in this genre, and through never having heard the noise while revving when not moving, I'm fairly convinced it's the plastic strip. Just need it to be warm enough to want to go outside and verify this. At least we've had essentially no snow here.

Dan

[smegin]

Foxcorner

Just lift the chain with a screwdriver, if you can see the heads of the securing bolts thats the problem. You don't need to test ride the bike. Believe me it is easy to see.

[oldndumb]

Originally Posted by cheefkeef

I had a think about your question ..........Fortunately we have a gear box fitted with a neutral gear and a clutch that can do this.
Good luck, Keef

Hmm, "gear box fitted with a neutral gear"? You sure about that?

[lovecuba]

Originally Posted by foxcorner

Hi all,

I'm enjoying my 2000 955i, but there is one thing I'm concerned about: When I come off the throttle, there's a clattering noise; sounds something like swirling gravel in a pan of water. It diminishes as I slow down, and is not at all heard when I'm at a stand-still, clutch in or out, or in gear. And the instant I'm back on the throttle (i.e. the engine's pulling the bike rather than the other way around), the sound vanishes.

The sound has enough high-frequency components (I'm an amateur recording engineer ) to suggest its source is external to the bike and not inside the engine.

I suspect it's the chain... it doesn't look like it's in the best shape in the world, but it's not apparently loose: there's no drive-chain snatch.

I haven't yet had the chance to set the bike on its center stand and play with the chain; and I probably won't in the next couple of days (forecast is a high of -4F and windy with snow...!).

Am I likely right about it being the chain? Or does anyone have experience / ideas about this kind of sound?

Thanks!

Dan

Quite normal! It is the alternator drive when on backlash. Sounds a bit like a 737 engine winding down. I love it!!!!!!!
The Gen 2 motor (2002 and above) have a different drive to the alternator which negates this wonderful bit of noise.

[Mark Savage]

Originally Posted by oldndumb

Hmm, "gear box fitted with a neutral gear"? You sure about that?

Well certainly mine has a neutral , when the green light comes on is a giveaway. I thought it was standard as I didnt purchase mine new, perhaps a special edition.

[dolson]

Neutral isn't a gear.

[oldndumb]

Originally Posted by markstark

any other engineering gems there chief

If you appreciate "gems" so much, why not take a look at the earlier post in which someone thought it was, and shared that "gem" with us.

[Mark Savage]

Originally Posted by oldndumb

If you appreciate "gems" so much, why not take a look at the earlier post in which someone thought it was, and shared that "gem" with us.

Oh dont get all sh!$$y, It was a joke, actually I had a couple of PMs about it as it was obvioussly just not put well rather than the poster/ member thought neutral was a gear. I have nothing but respect for your depth of experience I thought there was room for a bit of humour .

[kredge]

Originally Posted by markstark

Oh dont get all sh!$$y, It was a joke, actually I had a couple of PMs about it as it was obvioussly just not put well rather than the poster/ member thought neutral was a gear. I have nothing but respect for your depth of experience I thought there was room for a bit of humour .

Bet you got some more PM's...

[foxcorner]

I've done some on-the-centrestand testing, and... it's the drive chain. The engine's fine. No, it's not rubbing on a rub-strip bolt because... the bolt's gone!

So yes, I agree that I'll need a new chain and sockets and rub strip.

The front sprocket is 18-tooth, which I understand is a good upgrade for better fuel economy, relaxed cruising and better low-speed behaviour. So that's good; I'm glad it's got that already, and yes, the low-speed behaviour is just fine.

Question: Do they sell chain-and-sprocket sets with 18T front? Or will I need to look for separate parts? If so, what's the spec of the chain, since it's presumably not the same as stock so that it fits on the larger front sprocket? Or is it stock?

Thanks for all the advice!

It's just about warm enough to go for a ride today.

Dan