2006 F4i. I hear a rattling sound whenever I let off the throttle in any gear. Typically, I only hear it at lower RPMs (<8k), but I’m pretty sure that’s just because the engine gets so loud at higher RPMs and it probably is just drowned out.

It does not do it when accelerating/constant speed.

It has become more pronounced in the last few months.
Any ideas?

 

Have you inspected/lubed/adjusted your chain lately?

 

How old is your chain & sprockets set up?, Go for the usual bad guy, & this is mostly this. Have a look at the front drive sprocket condition, Even a cheap set will give you 40K
if you take care of them, but a set not cared for, can not last long at all, & you end up hearing this evil noise when the bike is coasting along with out any power being put to it.
C.W

 

So I will begin by saying I have been working on F4i's for about 2 years now. I am mainly an electrical wiring guy but grew very fond of the F4i after stunting it. The stock Cam Chain Tensioner should have been recalled from the factory because it's a POS. Every single person asks me what is that noise in my engine? Do you hear the rattling when I rev it past 3k? Buy an adjustable cam tensioner and please spend the extra $$ for it. You won't be disappointed when your bike purrs. If anyone needs any help with wiring or their F4i don't hesitate to shoot me a message.

 

Typically the chain tensioner lifter problem is not heard on decel but is with acceleration and only really between 5-6k not 8.

 

Its your Cam Chain Tensioner. Get an adjustable one.

 

Its a cam chain tensioner lifter, and I've gone threw 3 oem ones in the 12yrs I've had this bike from new so I know the fail pattern pretty well. What he's describing is not cctl noise, more like chain noise.

 

Id have to agree with chain/ sprocket.
I was getting a pretty good noise on decel last year before I replaced my chain. wouldn't do it while accelerating only on decel.

But if you want to rule out the CCT easily, rev to about 5000 rpm in neutral. Im guessing you wont hear the noise your describing.
The CCT makes more of a buzzing noise when it goes. Mines been replaced with a manual one I personally wouldn't go with an OEM replacement but I know a lot of guys
don't like the thought of aftermarket parts going on their bikes.

 

Thanks for all the replies. I lubed the chain about two months ago and didn’t notice the sprocket being worn (in accordance with the manual), but the chain was quite rusted.

 

Two months? Supposed to be done every 500 miles. If it has bern sitting, all the more reason to clean and lube it before putting the bike back on the road.