400 four knocking noise.

[LesterPiglet]

Upload your pics/videos to somewhere like photobucket.com and share the links.

[Lobo]

Cheers Lester...

Gawd, uploading pics enough of a palaver for me..., when I next get to my bike (late Sept), and assuming the alternative cam-tensioning method doesn't 'silence it'... then maybe the audio link will be the way to go.

Cheers,
Simon

[Lynx]

If it works it's here:-

http://s990.photobucket.com/user/Su_Lincoln/media/1200knock_zpscdaae29b.mp4.html

Steve

[Lobo]

Cheers Steve,

Tho' not as bad I think this is it! I've not actually felt the exhausts early on after start, ie by the time I have done this the bike has been revved & all too hot to linger & assess. Home again mid month & will investigate further.

Make sure you post 'the fix'. Were your cabs rebuilt with pattern of OEM parts / needles?

Simon

[Lynx]

Hi Simon,

The metal work all seemed good. I fitted new viton O-rings throughout. I made some new felt rings for the slide pivots. Everything else is original except I have new swapped the fuel valve, pilot fuel jet and float from spare carbs onto the pot 2 carb.

I think I'll throw on my spare carbs just to see what happens. I can't help thinking the is a small fuel or air passage in the carb somewhere that is still blocked with crud, even though everything seems to blow through OK with an aerosol of carb cleaner. They haven't be ultrasonically cleaner. Perhaps that is going to be the way to go.

[buxtonmick]

Steve, just a point; in the vid the initial revs are at 1400 rpm not 1200 

[mick]

I would try a fresh plug in that pot that's running cold that will make a difference when all 4 pots are running together, cheers  Mick.

[Lynx]

Thanks for pointing that out Mick .

It's not the plugs. I swapped 2 plugs but the same cylinder was cold.

[LesterPiglet]

No way was that bike revving at 1400. Something wrong with that tacho.

[Bitsa (Ralph Wright - RIP)]

Lynx
Sorry to state the obvious but until you get that cylinder running right you aint gonna get that knock to go.Shes dragging a dead piston.Can only be 2 things no compression or no fuel to it.
It really sounds like the carb to me.
Cheers
Bitsa

[Lynx]

Thanks Bitsa. I think you're right, especially as the knock goes at higher revs when all cylinders are running. So where in the carb do I find this fault/blockage?

[mick]

Probably in your idle & slow running circuits you may have to give your carbs more than 1 good clean to shift the stubborn dirt etc , ultrasonic is probably your best bet but if you haven't got that then carb cleaner and a a compressor for blowing through usually helps  cheers Mick.

[Clem2112]

Interesting..... been reading everything I can find about mysteries of 400/4 carbs ...here and elsewhere !!

Listened to that engine knock... heard that before !

My completely rebuilt engine (and carbs etc) does a similar-ish thing from cold.

After learning that the ethanol in petrol is a problem for our carbs and seals, I try to remember to run the bowls empty after a run. But if I don't....!!
...then after a day or two without running it will start only after lots of cranking, but No2 will not fire. Always No2 !!

I usually have to drain a bit of fuel from that bowl and then after a couple more attempts it starts on choke after a bit of coaxing. Bowl isn't full??
After a brief warm up it will  idle at 1200 rpm but only with the air screws set just one and a quarter turns out. Any more and it knocks and the idle speed drops could this be related to the float levels which I adjusted to stop the plugs sooting up.

On the road the engine now pulls well , especially above 5K if asked,  so the fuel supply is good. Only done 900 miles since the complete rebuild and it's been a tale of shortish rides and carbs-off for work.
Exhaust is standard OE (apart from the two pattern headers DSS supplied) as is the airbox etc.
I think the exhaust note is louder than I remember with my 1978 F"2" (yellow .. reg WGM508T) -  but that may be a symptom of this particular engine's state of tune - or just my memory of how quiet and civilised they were?.

Work on the carburettors....
Stripped for re-plating and inspection.
Were u-sonically cleaned individually (I bought a small cleaner from Maplin) and lots of compressed air to clear.  Fitted NOS floats, new OE needles, needle jets (tube), all new O rings. The floats were set using the clear tube+modified drain plug method (about 23/34mm after many attempts) so fuel all four levels equal and 7mm below joint faces.
Engine wise..
Tappets set to .002", ignition (Dyna-S) also spot on at idle and full advance.
Cam chain tension also OK. Camshaft measured OK when rebuilt.
Re-bored to 1st oversize, new rings, pistons. Re-shelled the mains and big-ends too.

Balanced the carbs to within half a cm Hg according to my old Davida vac gauges.
Each time the carbs have been off (half a dozen?, lost count) the bowls are spotless with no signs of deposits, gunk etc.
No longer overflow either-  I junked the Keyster kit items and re-fitted the original float valves after a through clean up and polish.
My thoughts are that maybe some excess air is getting in - could those felt seals be critical or some other item worn or corroded.
The bodies are apparently very sound and all the passages seem clear. I did read that new pilot jets sorted out idling problems on a  500 four, but mine look fine to me.

Nostalgia..
I got 400/4 fettling "experience" from working on my 1978 bike and clocked up 30,000 miles in all from new.
But the most I ever did or needed to do to the carbs was fit new main jets to suit a Yoshimura 4 into 1 (what a noise) and the bike never missed a beat... unless it rained or the points needed setting. Finally had to fit new tensioner blades and a head gasket to stop the infamous oil weep and chain rattle. 

 

[Lobo]

.... I'm at a loss too, though in my case doubt leaks in the felt washers areas: mine were in poor shape; and having failed to replicate successfully I fitted good quality / tight fitting rubber 'o' rings (which appear to seal nicely) in place of... ie can't believe any leaks possible here now.

Which begs the question why are they used in preference to standard 'o' rings - was it to provide a source of shaft lubrication; or to minimise throttle 'stiction'.... or what?

[Lynx]

Wow. Thanks for that. I did make my own felt rings. I haven't checked them since installing (such a pain disassembling that complicated lifting mechanism). If one of these is leaking air, will this effect the idle? I might have to go for the O-rings too. Do you have the right size handy Mick?