Bottom end knock

[Fish]

I am experiencing what sounds like a bottom end knock from my '07 Nightrain. The sound and sensation is intermittent and usually when pulling away.
Is this common, is there a known fault or cause?

[banquo]

Sounds like slack compensator sprocket nut perhaps?

[grbrown]

Might just be a slack primary chain slapping. When was it last serviced and by whom?

[banquo]

'07s have the auto primary tensioner I think....

[Fish]

Originally Posted by grbrown

Might just be a slack primary chain slapping. When was it last serviced and by whom?

Serviced by the dealer at 5k, then by me at 10k, but I thought they were auto adjusters so I didn't touch it, just changed the fluid.

I'll have a look at the primary chain, what's the allowable deflection on the chain?

[Urrell]

Motor mounts secure?

[grbrown]

Originally Posted by Fish

Serviced by the dealer at 5k, then by me at 10k, but I thought they were auto adjusters so I didn't touch it, just changed the fluid.

You may be right - I am happy to be proved wrong!

I'll have a look at the primary chain, what's the allowable deflection on the chain?

That will be in Section 6 of your factory service manual! None of my bikes has an auto adjuster as standard.

[jjrjear]

Originally Posted by Fish

I am experiencing what sounds like a bottom end knock from my '07 Nightrain. The sound and sensation is intermittent and usually when pulling away.
Is this common, is there a known fault or cause?

I don't know if it's a common problem or not. I had the same unnerving knock coming from the bottom end of my '04 Road King. I thought it sounded like a rod knocking. Well, come to find out it was the rotor on the charging system. Seems the factory either forgot to install, or installed the wrong size shim behind the rotor. Which after a few thousand miles ate up the splines on the rotor and caused the knock at idle, or like you when releasing the clutch to take off. If you're still under warranty, take it to the shop of your choice and have them check the play in the rotor. If you do it yourself it involves pulling the primary off and loosening the primary chain to check it. On mine the splines on the rotor were completely gone. I had to replace the rotor. It's not a terribly expensive fix if that's what it is.
Hope this helps you.
Thanks, JR