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Messages - K2-K6
1
« on: Today at 10:36:39 PM »
I'm not sure they had any fitted to them, no trace of the fitment in Honda's own workshop manual that I've got.
Correct carburettor for the bike PD41B with the K7 sharing type but denoted as "A" spec. I think it was only production line designation to facilitate different jet sets between the two.
Looks like they breath just through the overflow/vent tube (going out from spigot on float bowl base) from outside, with the interconnects just giving an linked atmosphere across the four.
If not aware of this design, the idle mixture adjust screw is fuel not air in this carburettor.
I know there's not very good "enthusiasm" for the PD type, my view is that they're one of the the best metering production slide carburettor made, particularly in respect of ideal mixture plus enrichment for acceleration only when needed.
Slide lifter on choke too for fast idle and warm up.
I've access (limited) to an original one my friend bought new if there's need to check further in practical detail about vent pipes etc.
2
« on: Today at 11:09:27 AM »
It may not be cold enough ambient to need full choke at this time of year in starting it. Worthwhile trying at 1/2 to judge effect.
Many bikes of this era have no throttle interaction with "choking" application, its just down to you to open the throttle a little, as appropriate, to balance demands at this cold start phase of running bikes like this. That's entirely normal and expected.
The end of line SOHC models variously had the throttle and choke linked to give the effect that you're doing manually here.
It does sound particularly good in running and cylinder to cylinder parity. If anything, it's "hunting" slightly (a little excess fuel at that independent running point) which is detectable in minor way.
A couple of miss/stumble hiccup heard, likely to be the plugs having not fully warmed from riding out on it (typical if just standing with no load ) that should disappear when all up and running.
As you note, fully assembled intake system to be installed, then see what you've got at that point.
It is very smooth though. Any competent workshop would be proud of that result.
3
« on: October 21, 2026, 06:20:50 PM »
That sounds really good in the yt clip Neilw.
Bang on the money for carb balance, so much so that I wouldn't change that at all.
From an interest point of view to us out here, a clip of it with gauges hooked up to show what they read would be interesting. But I'd not change the balance set you've got .... even if the gauge suggest any variance.
Well done with tbe detailed work, very frustrating at times, isnt it? That's very good progress there that you've got too.
"White smoke " is just vapour from combustion before the cylinders and exhaust have got fully warmed through. That'll disappear when fully up to temperature, perfectly normal from cold start in engines.
4
« on: October 21, 2026, 05:18:32 PM »
Aah! The choke on any carburettor is described as ON when its restricting airflow by shutting off the incoming air. That's it's starting/cold position.
Choke OFF is with the restriction of incoming air least affected. This is normal/warmed up running position.
5
« on: October 21, 2026, 07:52:47 AM »
He did tell us it was difficult to keep clean as the SS bodywork on the prototype was a sort of brushed unsealed finish that rain spotted badly.
I've heard about that brushed metal on at least some parts of the bodywork of DeLorians, but the issue raised was it was near impossible to deal with any scratches et al it picked up. Did he have long white hair, did he ever discuss the future? 
Ooooh! The trouble with those is (apply nasal overtones here) you can't get the Flux Capacitors for them  once they go you've had it with these time shifting machines
6
« on: October 20, 2026, 08:39:06 AM »
I was wondering if scottly was questioning if there was a petcock on the auxiliary tank, and if that had any parts in it with this potential.
I know some have a metal petcock as others have a simple plastic clamp external to the feed pipe.
7
« on: October 20, 2026, 07:55:32 AM »
Could the rubber bits be coming from the rubber sealing washer inside the petcock?
On the auxiliary tank fuel supply ? I don't know what config is there, but running some fuel i to clear container should show anything not desirable.
8
« on: October 19, 2026, 07:34:31 PM »
Logic would be there's something caught somewhere inside the carbs and their fuel distribution, but puzzling as you say.
A suggestion to consider, if you've a steam supply (wallpaper stripper or the like of) you can make a small nozzle out of something like brake line pipe, then blow steam through all the orifice and pipes to see what comes out.
It's something I've used before in chemical lab work to clean various apparatus of debris as it'll usually free up anything stuck inside crevices etc to flush out comprehensively unwanted contents effectively. That can be "tarring" or residue stuck to surfaces you can't see.
9
« on: October 19, 2026, 07:05:40 PM »
Are you supplying from auxiliary fuel feed ? Not the bike's tank.
10
« on: October 19, 2026, 08:40:35 AM »
Nice work archmill. Good thinking about the approach and test piece to establish limits of tolerance.
It's not that often these Honda sprag fail generally. Something that's apparent from running earlier Triumph Hinckley triples is importance of having decent battery output. If they are anything slow in turning over, then sprag clutch is vulnerable to excessive wear on those.
At least there's kick-start on these Honda of the era.
11
« on: October 15, 2026, 09:21:54 AM »
Put a spare plug in a lead and start it with that held to earth, will verify you've got coil output.
12
« on: October 13, 2026, 09:34:22 AM »
At this point tge zim is to make sure you feel got fuel supply free from chunks and the idle jets plus side passages flow cleanly as they should. It should be useful to run the airscrews at just one turn without the airbox in place, but only for that reason temporarily. What you're looking for is start and warm, gradually retracting choke until it'll run at idle without interference. Essentially its establishing if the idle circuit are clean and functional. Then it can be moved onto fully installed intake and should respond logically to fine adjustment with that all in place. Likely it won't respond to "snap" throttle opening well, or if you tried to ride it and ask for productive torque.
13
« on: October 13, 2026, 08:32:11 AM »
The suggested action is correct.
Essentially the engine idles almost exclusively on the fuel metered through those idle jets, the main, plus needle fuel route virtually closed with throttle closed.
Using choke, causes the vacuum in intake tract to rise, leading to fuel being pulled through both main jet and whatever it can get via idle jets .... that fuel will not be pulled through those routes (if partly blocked ) without the increase in vacuum the choke gives. Hence the stall when choke is fully opened.
Sound logical?
Your description, experience and the gpt effectively agree on cause.
Thank you, i'm floundering around in the dark tbh, so your opinion and explanation is very helpful. I'm getting a master at whipping the carbs off/on, having done it so often, so that's my job tomorrow.
As you're finding here, substantial part of good running is dealing with problems that simply prevent the components working as they should. Not optimisation as such, but a little frustrating in chasing things down completely to enable the normal functioning in the chain of parts that interact. A good description of fault, as you've provided in observation here, will allow us to point at probable cause to help in untangling those symptoms. It may be helpful, to run without the airbox in making it easier to pull carbs on and off at least while getting a baseline established that will see all idle circuit clear and functioning. This won't allow or facilitate good analysis in riding it, but just speed up the frustrating part (most have to go through this ) of getting fuel system fully clean and flowing as it needs to be. At that point, a full fit and test with everything in place should give a much better picture.
14
« on: October 12, 2026, 07:32:28 PM »
I've bought and used fuel pipe from here https://www.ebay.co.uk/itm/405924654488?var=676233395444Honestly described and so far it has not been affected by deterioration. It needs more evaluation from anyone on here to back that up, more specifically in leaving it containing fuel over greater length of static/low use scenario in providing more extensive feedback. So far, no observable failure for me.
15
« on: October 12, 2026, 05:14:53 PM »
The suggested action is correct.
Essentially the engine idles almost exclusively on the fuel metered through those idle jets, the main, plus needle fuel route virtually closed with throttle closed.
Using choke, causes the vacuum in intake tract to rise, leading to fuel being pulled through both main jet and whatever it can get via idle jets .... that fuel will not be pulled through those routes (if partly blocked ) without the increase in vacuum the choke gives. Hence the stall when choke is fully opened.
Sound logical?
Your description, experience and the gpt effectively agree on cause.
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