400 four knocking noise.

[K2-K6]

I'll have a go at describing the sequencing there with what you've got.

The drive from the crank passes to the clutch, this is essentially another flywheel albeit remote from the crank. A flywheel wants to spin at a consistent rate (the main reason for putting one on a crank) and imparts it's inertia backwards down the primary drive route if there is a change in crank speed.
Bare with me while I try not to confuse myself here!
When the engine is running then for one crank revolution you will get first one cyl firing while it's paired piston is at tdc at no compression, and the other two pistons at the bottom of the stroke....this is then reversed for the other two cyl.....now these small four cylinder engines sound very smooth but at low rpm there is significant crank speed fluctuation when ever one pot fires as it first comes up to compression (only one cylinder doing this at a time remember) the crank slows, followed by acceleration as the ignition fires that cyl.
That speed change comes through the primary drive BUT is opposed by the clutch which is happily spinning consistently as it has no balance issues.

If you think of what happens to the primary chain top run as the crank slows but the clutch keeps spinning it should go slack momentarily....followed by a whack as the crank speeds up faster than the clutch inertia.......it's this, I believe, that the clutch cush drive is supposed to mitigate, i.e. when the chain twangs it's the cush that should allow some give to stop that being a mechanical clunk that you can hear from outside.

So if the cush drive has gone hard and it should have some elasticity when new, then the small shock load it should be absorbing is just not happening.

You can even get a good demonstration of exactly this process if you put most bikes on the centre stand and let the engine idle.....put it in third or fourth gear and watch the final drive chain as it clatters up and down (the rear wheel being a sort of flywheel will replicate the primary drive inertial effects only on a larger scale).

So in principle I'm saying that there is not enough controlled movent in the clutch cush drive and it's most likely that most older examples would be similar.

See what others reckon.

Nigel.

[Lobo]

Hi Nigel / OddJob,

First up that thrust washer thought is giving me a sleepless night; I didn't take one off, or put one back. Bollocks! In truth I'm thinking it simply remained in place on its shaft whilst I verified the no-basket rattle fix - mainly because I DO remember, on reinstalling the castellated nut only a thread or two (at most) exposed post tightening. Working in a bit of a rush etc!

Nigel... thanks for the explanation - which all makes sense....apart from the 'bag of nails' cacophony - ie a mixture of metallic sounds. Is it simply the components of the basket make-up, all the rings etc rattling individually - there are for sure an 'awful lot' of parts.  This all said, I would have thought an engaged clutch (ie lever in normal position) would be tight enough not to allow individual components to rattle.
Have taken a punt on a 2nd hand basket, and by way of a project plan to order a shiny set of those red cushes above.
Cheers for your thoughts / help,
Simon

[Clem2112]

I follow that...

The generator rotor also adds mass to the crankshaft mass to help reduce the speed fluctuations but there still isn't much flywheel effect overall.

The noise may also be worse if the cylinders are not all producing the same shove at idle?

When I had my original bike the knocking noise was less evident when the carbs were balanced and the timing was spot on.
Some bikes are also a lot quieter with the clutch disengaged. This de-couples the gearbox which mean less mass to be sped up and slowed down with each rev of the crank to reduce the noise.

[ttr400]

Hi Lobo, sent you a PM. seemed to hang up when sending so not sure if it went through?

Kevin

[ttr400]

Hi Simon, thanks.  sent you a PM.

Damper rubber kit, posting today via registered airmail.

Kevin

[LesterPiglet]

Posting on this forum is sketchy. I think they are sent but you recieve a blank screen.
Search is marvellous though, I wish they would fix the US one.

[keike]

got the same on my little winged honey...she's idling at just over and around 1000 - 1200 ish ...but I won't get too hung up about it - it seems they all do that sort of thing? More or less? Higher idling speed, as you said at around 1800- 2000 ish (might be far too high I think?) and the tractor feeling is gone...so I dunno...My boyfriend used to dispatch ride on several 400/4 in the early eighties around Ireland and says my sound might come from the hyvo chain...comes with age? - who am I to kid here?
...no, and I won't strip the engine-again!

[Lynx]

Dear Clem2112,

Have you fitted the new rubbers yet?

[Clem2112]

Lynx....

Err ..Not quite ! 

I've been waiting for my cylinder head repair so I can put the top end back together.
Since I am still waiting, Now about to take the clutch out and begin surgery on the basket ....
I'll get some pics of the operation on the forum as I go.

[ttr400]

Lynx, i sent you a PM, not sure if it went through.

Kevin

[Clem2112]

First reply failed.... probably because I tried attaching too many photos.

Anyway the clutch basket rivets are all out now.

They needed some extra persuasion though...

Drilling the flat heads off freed the retainer plate.
 
Since the other end (or upset) would be gripping the hole, I drilled into that as centrally as I could (punch mark first)  with a 3mm drill about 6mm deep. Then 4mm drill to the depth of the deformed end to weaken it a bit more.

The old dampers were a lot better than I imagined. Still flexible but had shrunk slightly. Also some small cracks around the centre slot corners.
The Honda ones have an asymmetric shape with cutouts too -  the new ones are symmetrical and full form but should do the job and without the backlash. Pictures will follow.

Next comes the threading ... WD40 is recommended it seems.
The holes are already about 4.2/4.3 diameter (a new 4.2 drill is a slack fit). 4.2 is the spec for M5x0,8.
The depth of thread will be about 14/15mm ... satisfies the 3x bolt dia rule (ish).
Also have to drill out the plate holes to clear the bolts.

to be continued...

[Clem2112]

Yes, the rivet holes are being tapped.

I thought inserts might be needed too..... certainly if I mess up tapping the first hole !

A small tack weld on each bolt edge to the plate might be a belt and braces way... ??

Kevin (ttr400) says to use red Loctite to lock them for good- he has done a few.
Since the bolts (hopefully) never need to come out again this should suffice.

I'll see how the fit of the bolts "feels" ... I know a local place that just helicoiled my cylnder head (again)

[Lobo]

Is there enough 'material' in each of the 6 'lugs' (?) to drill a size up and helicoil? Must all be getting a bit 'thin' I'd have though.

Very interested in this one Clem (Simon) as my cushs in the post & this task pencilled in for me soon. Keep the good info coming.

Lobo (Simon #2)

[Clem2112]

Is there enough 'material' in each of the 6 'lugs' (?) to drill a size up and helicoil? Must all be getting a bit 'thin' I'd have though.

True, there is only 2 or 3 mm to the lug sides... hence only an M5 not M6 bolt.

[ttr400]

Helicoils are not required. just tap to M5.

Kevin