I was getting ready to come home from work tonite and when I started the bike up (NC30) it had quite a bad knocking noise. When I got home (its only a 10 min ride) it had quietened down. I have no idea what it could be so any advice on where to start looking? I know without seeing/hearing it you cant really say but any random guesses on what could make a knocking noise from the engine? I plan to do the carb mods at the weekend and think I will do the valve clearances while I'm halfway through stripping the bike. I've had it a week and only been out on it 3 times!

How much of a knocking..like an actual loud knocking?

if so..then my experience is that you had better find out asap what that is...and that my guess is bottom end bearing failure..so don't ride it 'til you find out.

I'd not normally say so..but get a video of it on here asap -

If you said tapping, ticking, clicking or pretty much anything other than knocking, I'd say something loose, exhausts blowing etc.

Hold off on your carbs and any fucking about -you might be swapping an engine yet!

Ok, so I would say it is more of a tapping noise I think? It wasnt as bad today and I think it sounds worse cos the exhaust makes a bit of a thudding noise too (aftermarket beowulf with no baffle). Its very hard to describe noises! I dont think its as bad as I made it sound but still want to know what it is! I will try and sort a vid for tomorrow.

If the noise went after 10 mins and was less the next ride, then sounds like engine is OK.
Was it/is it running on all 4 cylinders, if not, the one not firing will rattle.

Are all ex pipes getting hot at tickover?

Could be ex or something vibrating against the frame parts.

I once had a terribly worrying clattery sound come from my NC35 that only seemed to happen when stationary and you blipped the throttle, though it wasn't loud enough that you'd have been able to tell if it was happening while out and about, especially as I wear ear plugs. In my case, it turned out the the lips, bands and collars on the front header to collector joints were shot to oblivion, and the whole lot were rattling about with the vibration of the engine at low rpm! A combination of my friendly mechanic and the custom bike fabrication shop next door whipped the lot off and welded new lips on the headers, and all was good.

I would say that if you're new to the bike, 9 times out of 10 it's just regular valve train noise that gets louder as the engine (not necessarily water temp) gets hotter. The valve train can get quite tappety, and not always a sign that valve clearances are out.

Hoping for that it's just normal noise.

Sorry just reread your post and if it's making the noise from cold it's unlikely to be normal, but could be a number of other things as said above.

Mine's quite loud when cold, but I put that down to old age and the fact that's it never really been very quiet. It's certainly not excessive or abnormal sounding. I'm quite sure that if there was anything up with it to create the noise rather than it just being a characteristic of the engine, after putting almost 80000kms on it since I've had it, it would probably have blown up ages ago! lol

Hmmm, i'm getting a bit confused now?? I took my phone out to video it and........
nothing! it ran sweet (apart from revs seem to be a bit up and down at tickover but hopefully sorting carbs out will remedy that).
I know I wasnt imagining it cos there was someone else with me when it rattled/tapped/knocked??
Hopefully it was nothing to worry about and i'll check for loose stuff when I strip it at the weekend.
The indicators are playing up and come on about 5-8 seconds after flicking the switch so I have to put em on ages before a junction. I will be stripping and cleaning the switches as well as doing the carbs and valves now!

Well, that is better news - better it be quiet than fucked!

Same thing happened last night. A washer and a nut holding the seat fell off onto the engine and kept rattling there. I really dislike how the seat is fixed to the bike (nc30).