Help - my engine rattles

[Cadwatta]

Hi everyone. I don't know if anyone can give a bit of advice here. I have only had this bike a week or so, but when cold there is a rattle on tick over from the gearbox/bottom end. It's a 1994 CB400F2N, with only 8000km on it and this mileage looks genuine, with a load of old MOTs. I have looked at filters, plugs, oils etc and based on this, the clean edges of the gaskets, and the sound of state of the motor and cycle parts, it really looks as if it has hardly been used. The bike was warm when I picked it up (yes, I know - I should have gone away for a while and heard it cold) and rode it home (200 miles) and everything was smooth with no undue noises or clatters. Now I discover that it is noticeably rattly but only when cold and only when ticking over. I have looked at the russian manual but can only see an oil pump chain, so now i wonder of it is the gearbox - the noise goes as soon as it takes up a little drive. But I can't believe it's been abused to this extent. Can anyone tell me if they are usually noisy when cold and have I anything to worry about? Maybe it is because the gearbox is in engine oil? Cheers.

[houdini]

sound like your cam cahin get it checked before it snaps i didnt and now it's gonna cost mucho bucks to fix my sf

[Cadwatta]

Oh, sorry to hear about your cam chain and thanks for the reply. After I posted my appeal I realised that there was actually a cam chain - I think I thought it was gear drive. I also thought that a cam chain might rattle all the time and not go away when hot and not go away as soon as I put a little bit of throttle on. And the fact that it has done so few miles. Do you know if there is a tensioner and adjuster? Cheers

[BUGIE]

I don't know if i'd call it a rattle but the bike does make a ticking noise when the bike is cold...
That's normal as it's just until the oil gets around.
It should only last 10-15 seconds at most.

[Cadwatta]

Hi Bugie. Pleased to meet you (so to speak). I listened to it again last night. It is like a bag of nails when cold, for a few minutes, not seconds, but after a short run it sounded fine, running smooth. The whole bike looks like new and I am sure it is not a tart up. It is not tappets and I would expect a worn gearbox to stay noisy. Piston slap would be regular but this isn't. So I guess it must be the cam chain, as Hudini says, or just normal. Maybe i am getting paranoid. I am right in saying the gearbox uses the same oil as the engine aren't I?

[poshman1]

My 99 superfour vtec knocks quite abit when cold and it does sound like a bag of nails. its nothing to worry about it is just the oil getting round. Mine is wore the colder the weather especially on frosty mornings. Use plenty of choke and it will soon warm up an go away! Rest assured

[Cadwatta]

Thanks for the reassurance Poshman 1. I appreciate it. I have noticed that the noise is only there when the tickover is lower than the prescibed level ( for example when I start it from cold with not enough choke) and that as soon as it gets over about 1000rpm, the engine sounds ok, which of course is the situation when the engine gets warm. So like you imply, I think I have come to the conclusion that it must just be a noisy engine. I have a 325 mile trip to Plymouth soon, so I feel a bit more at ease now. :)

[alexibrow]

There's a difference between a small amount of tapping/ticking and a knocking noise like "a bag of nails".

If anyone's engine knocks when cold like a bag of nails, there's something badly wrong that should be investigated and rectified immediately, to avoid causing any more damage.

[BUGIE]

I think the "bag of nails" is open to interpretation... After all he didn't say how hard you have to shake the bag of nails to replicate the noise

But Alexibrow is right - There is a distinct difference and it should be a slightly noticable noise as opposed to very loud one.

Alexibrow - Did you get your new bike?

[alexibrow]

Not yet Bugie; I'm going to give it a proper going over on Friday before I decide.

I'm struggling with the idea of selling the Super Four though...