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Honda 400 four engine noise

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scamper
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PostPosted: 22:07 - 24 Sep 2021    Post subject: Honda 400 four engine noise Reply with quote

Just had some service work done on my 400 four. Now it's back I seem to have this metallic vibration/rattle that starts at about 2,500 rpm. As far as I can tell it appears to be coming from the area behind the Honda cover at the bottom of the engine on the left hand side.

The chap who did the work said the bottom end had a bit of a rattle which would need some work at some stage but I think this is different somehow. Any thoughts as to what it could be? Is it possible to take the left hand casing off to see what's going off without stripping the whole thing down?

Could it be the cam chain needing adjusting? Not sure I know what that sounds like anyway.
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xX-Alex-Xx
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PostPosted: 22:33 - 24 Sep 2021    Post subject: Reply with quote

What side is the cam chain on? If it’s loose it’ll sound like a ball bearing rattling in a can, and get worse when you lift off the throttle.

The Honda automatic cam chain lifters are typically shit. Usually a good idea to replace with a manual one.
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A100man
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PostPosted: 08:20 - 25 Sep 2021    Post subject: Reply with quote

xX-Alex-Xx wrote:
What side is the cam chain on? If it’s loose it’ll sound like a ball bearing rattling in a can, and get worse when you lift off the throttle.

The Honda automatic cam chain lifters are typically shit. Usually a good idea to replace with a manual one.


Classic 400/4? Up the middle like all UJMs.
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A100man
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PostPosted: 08:24 - 25 Sep 2021    Post subject: Re: Honda 400 four engine noise Reply with quote

scamper wrote:
Is it possible to take the left hand casing off to see what's going off without stripping the whole thing down?



Some one here will know. probably just some non-oily ignition gubbins or generator. Get a manual or check diags on CMSNL before dismantling.
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bikenut
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PostPosted: 11:15 - 25 Sep 2021    Post subject: T Reply with quote

Yes, check on CMSNL exploded views, such a good free resource so you know what's there and where....been recommending CMSNL for the very informative info therein.

No I do not work for them as has been mentioned by the Thomases.
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steve the grease
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Joined: 26 Jan 2018
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PostPosted: 14:50 - 25 Sep 2021    Post subject: Reply with quote

Years in the motor trade have taught me that " what happened last" is a very powerful diagnostic tool.
'Oh , I've just filled it up with petrol' -Ocams razor tells us that there's a 97% chance that - No you haven't love, you've just filled it up with diesel and that is why you are stopped at the side of the road. Etcetera.

So -what servicing work did the bloke do - what did he remove ( and hopefully replace) ? Is it possible that the servicing work has uncovered some underlying fault? Has something been left off, or not tightened up.
Theres not too much happening on the left hand side of the engine - generator and the starter clutch - does it sound ok when it's cranked over ?
Good point about the chain, it's the main thing going on along the left hand side. - is it tensioned correctly - not too tight? - the tension ideally should be checked with the rider on it - so 1/2 inch to an inch ( or something like that) with the riders weight on the bike. Not when it's up on the stand with no one sat on it, for example, meaning that its like an iron bar when you are sat on it.
Just some observations .
Good luck
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scamper
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PostPosted: 20:14 - 25 Sep 2021    Post subject: Reply with quote

A100man wrote:
xX-Alex-Xx wrote:
What side is the cam chain on? If it’s loose it’ll sound like a ball bearing rattling in a can, and get worse when you lift off the throttle.

The Honda automatic cam chain lifters are typically shit. Usually a good idea to replace with a manual one.


Classic 400/4? Up the middle like all UJMs.


Yes 1975 F/F1 varnish blue. From what I've read straight up the middle. Thumbs Up
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scamper
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PostPosted: 20:17 - 25 Sep 2021    Post subject: Re: T Reply with quote

bikenut wrote:
Yes, check on CMSNL exploded views, such a good free resource so you know what's there and where....been recommending CMSNL for the very informative info therein.

No I do not work for them as has been mentioned by the Thomases.


What's CMSNL?
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scamper
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PostPosted: 20:25 - 25 Sep 2021    Post subject: Reply with quote

steve the grease wrote:
Y

So -what servicing work did the bloke do - what did he remove ( and hopefully replace) ? Is it possible that the servicing work has uncovered some underlying fault?


That's a good point. The engine was a bit rattly, nothing too serious. I think he did the usual service, oil, tappets, camchain, points and plugs. He did find a problem with the spark plug on the left. The cap/lead had burnt out. This could have unearthed another problem. I don't think it is too serious. I'm just hoping it's something not screwed down properly and it is an easy fix otherwise I might have to get back to him.
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A100man
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PostPosted: 07:46 - 26 Sep 2021    Post subject: Re: T Reply with quote

scamper wrote:
bikenut wrote:
Yes, check on CMSNL exploded views, such a good free resource so you know what's there and where....been recommending CMSNL for the very informative info therein.

No I do not work for them as has been mentioned by the Thomases.


What's CMSNL?


Ta da!

https://www.cmsnl.com/honda-cb400f-england_model14639/partslist/#.YVAW8UbTV1Y
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bikenut
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PostPosted: 14:54 - 26 Sep 2021    Post subject: T Reply with quote

Yeh, lol....

He found bcf, how I wonder...still he knows now, as do others that don't know what Google is.
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blurredman
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PostPosted: 09:52 - 27 Sep 2021    Post subject: Re: T Reply with quote

bikenut wrote:
Yeh, lol....

He found bcf, how I wonder...still he knows now, as do others that don't know what Google is.



One of those rotary links on other websites.. Cool

Used to have to sign up and be 'a team' with a bunch of other websites that promised to put a link to you, if you did of theirs.

There was once a world without Google.. Embarassed
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UnknownStuntm...
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PostPosted: 21:09 - 28 Sep 2021    Post subject: Reply with quote

scamper wrote:
That's a good point. The engine was a bit rattly, nothing too serious. I think he did the usual service, oil, tappets, camchain, points and plugs. He did find a problem with the spark plug on the left. The cap/lead had burnt out. This could have unearthed another problem. I don't think it is too serious. I'm just hoping it's something not screwed down properly and it is an easy fix otherwise I might have to get back to him.


Cam chain rattle is built in to those bikes. What normally happens is some divot who thinks they know how the adjuster works monkeys around on it until it snaps, then the adjuster is locked into its position or it actually loses all tension until you split the cases and rescue it. It's quite simple to actually adjust it, more simple than the tappets imho.

Other things that can cause a rattle are (maybe order of likelihood?):
Poorly adjusted carbs
Poorly adjusted timing
Loose headers (they don't need to be done up really tight, like 10nm will do)
Loose stuff on the outside of the bike
Engine internals

In short, ask yourself if he's actually finished the work or should you be thinking about taking it to someone who knows a bit more.
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