something in the middle of my bmx is making a donk noise?

[HovR]

not helpful, but donk related
Blackout Crew - Put A Donk On It - Out Now: http://youtu.be/ckMvj1piK58

See, I think we might be taking the wrong approach here. Our good old friends at The Blackout Crew are suggesting we put a donk on it, when I suspect that in fact we may actually need to remove the donk.

Yeah, this track was the first thing that came to my mind too.

To the OP, if you are sure that all the bearing surfaces are smooth, with plenty of grease, and are well adjusted (no play, but not too tight) including the pedals, and you still haven't found the source of the donk, try giving this article a read. Try solutions for other noises as one mans donk is another mans knock.

http://www.jimlangley.net/wrench/keepitquiet.html

It's also worth checking the headset is well adjusted. With the front brake applied, rock the bike back and forwards from the handle bars. Is there any play? There would probably need to be significant play to cause a donk, but stranger things have happened.

 

[Smurfy]

I'd advise leaving the grease in his hubs. Replace it with fresh stuff, by all means, but don't just wipe away, it's kind of important.

Edit: Unless you were meaning wipe the grease away to check the bearing surface, then replace, in which case valid suggestion, and my mistake!

LOL. Yes, I meant wipe it away to have a look, rather than wipe it away and run the bearings dry!

 

[tyred]

You may have sticky pawls in the freewheel.

 

[leefreeman97]

I took my crank out completely, I cleaned it all out and re-greased it then put it all back in and the noise was still happening so I took my back wheel off and took the bearings out, completely cleaned the inside of the wheel and the bearings. I also made sure all the screws that hold the spokes in were tight then I put the wheel back together and put the wheel back and the noise had quietened down a bit so I did the same again and took the seat pole out cleaned it and put it back in then took the pedals off, greased the screw bolt that tightens the pedals and then put them all back on and tried riding it. Now the noise is still there but barely noticeable so this has helped and the noise is better than what it was before I did all this.

 

[themosquitoking]

So everything was creaking in time? Get your bike onto an obscure BBC arts show asap.

 

[I like Skol]

I was about to say that maybe you have a broken spoke that is catching once per revolution. Maybe this isn't too far away from the problem as you say you have tightened the nipples (the bits at the rim that the spokes screw into) and the noise has reduced. Perhaps you had/have a loose spoke. Go around both sides of both wheel and pluck the spokes to see if any sounds a lot duller than the rest.