Topic: 400F sputtering/rich at idle

[DaveBarbier]

Also, I’m not getting continuity between the “gazouta” 1-4 & 2-3. These are the spark plug wires with boots off.


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Then select higher scale, knowing 200kΩ. What plugs do you run, the "R" type or the nonresistor type?

Ah Delta beat me to it.

[minimo]

Also, I’m not getting continuity between the “gazouta” 1-4 & 2-3. These are the spark plug wires with boots off.


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Then select higher scale, knowing 200kΩ. What plugs do you run, the "R" type or the nonresistor type?

But was I to measure Ω or continuity per the faq, which are different settings on my MM? But I suppose getting any kind of Ω reading is pretty much the same as continuity, right?

I’m using NGK D8EA (2120) spark plugs.

After I get on some new plug caps I’ll throw on some fresh spark plugs too and shall we give it another whirl?



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[minimo]

Also, I’m not getting continuity between the “gazouta” 1-4 & 2-3. These are the spark plug wires with boots off.

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Then select higher scale, knowing 200kΩ. What plugs do you run, the "R" type or the nonresistor type?

By golly, Deltarider, u r a genius.
MM set at 200k, I get 14.3 across 1-4 and 2-3.

So my coils seem, ok, right?



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[Deltarider]

Yes.
@

one meter connects to black/white the other connects to plug wire:

No, that doesn't make sense, as they're not connected anyway.

SPARK PLUG CAPS
#1 = 8.88
#4 = 11.23

I personally find #4 is a bit too high and should be discarded.

[minimo]

Thanks, guys.

I’ve gone ahead and replaced all spark plugs caps with fresh NGK ones - pruned all the wires back about 1/8”. Got the new spark plugs in there as well and torqued them down evenly to 10 ft/lbs. I also cleaned up the old condensers as best as I could. As for the points (stamped with “ND” - Nippon Denso)I sanded down some peaks yet there was a small pit on both the upper points for both 1-4 and 2-3. But I did my best to make them as even as I could using 600 grit sandpaper and then polished with a silicone carbide Dremel wheel. Battery is on a fresh charge and I got 1-4 gapped and adjusted. I’m now having difficulty getting 2-3 to land on F. I try lining up the mark tangent along the 2-3 spring post as a reference and gapping it at 0.3mm but it’s firing somewhere passed the F and before and sometimes on the T. The Plate adjustment on 2-3 is also max’d over. What Can I do? Is my gapping correct? Is there a better way to gap 2-3?
this image shows where I measure the gap using an imaginary tangent line along the left of the spring post. Is this good?

Is there a good way to “retard” the firing on 2-3?


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[DaveBarbier]

Running out of room on the points is common. Here's a good write up from TwoTired: http://forums.sohc4.net/index.php/topic,5752.msg47539.html#msg47539 Hope this helps. Some also fix this issue by going to either the minimum or maximum points gap...I forget which

[minimo]

Thank you, Dave. This seems very helpful.


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[minimo]

Thanks again, Dave. With TwoTired’s info I was able to get spot on, statically speaking on both 1-4 and 2-3.

Well, fired her up and here’s where we are on the plugs:

From sooty black #1 to wet #4.
#4 header was warm and got progressively hotter to the touch up to #1 - at least there seems to be some kind of sequence; not a favorable one. Ugh.

I tried to quickly strobe #4 and #2 respectively and I got the plate to hitter around their F marks. That’s when the bike began to sputter at idle again and without throttle would simply shut off.

An interesting finding under the bike where the muffler and headers mate:
just a bit of moisture. It doesn’t smell like fuel nor oil. Maybe a tinge of stagnant water. I removed the muffler and it was dry and all sooty.
From what I understand, this is not a stock muffler but it shouldn’t make too much difference, right?

Meanwhile, no overflow of fuel from the carbs. Air mix screws backed out at 1.5 turns (stock).
Still seems rich, at least on 1-2...


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[minimo]

So, what do you think, fellas? Is it time to pull the carbs again and maybe this time check the throttle body needle clip positions?

Any (Amazon) links to the JIS screwdriver I need to get to access those two tiny Phillips screws?


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[minimo]

Tempted to order a size down from stock slow jet. Anyone have luck running 38 pilots on a stock 400f?


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[Deltarider]

Two things on ignition: 1. You are aware you're supposed to set the breakerpoints gap before adjusting timing, aren't you? 2. When using a strobelight with inductive clamp, there's polarity to be observed. If the gun lights irregularly, try flipping the induction clamp. "THIS SIDE TOWARDS PLUG" that we often read on these clamps is only true for one of the two HTleads coming from a dual output coil (wasted spark system).
Now to the plugs. BTW I agree with those that say most carburetor problems turn out to be 'electrical'. But already from the beginning I have the feeling your problem is carb related. When I look at plugs #1 and #2, I can't think of an ignition problem unless you're having the two HTleads to #1 and #2 plug too close to one another and so causing interference. Not very likely. Arcing between HTleads and/or caps to the head (= ground) is seen often however (best checked in the dark). If that's not the case, I'd say cyl. #1 and #2 either receive too much fuel or too little air. If it's too much fuel, another close look at the near idle carburetion. A cleartube test of the fuel level in the floatchambers is worth trying. Are you sure the floatneedles close well? Test is to detach the overflow tubes, leave the petcock on, wait for 10 minutes and see if fuel exits the brass overflow tubes under the carbbowls. I remember you reported the O-rings around the mainjets seal well. If you ruled out blockage of air (like hanging chokeflaps), you could try opening up the airscrews #1 and #2 even more or have smaller size slow jets installed. You çouldn't have widened the slow jets in the cleaning process, could you?
In the event you have the carbrack on the table, you could check, after removal of the mainjets, if all 4 needles are hung at the same height. Checked from below so to speak. At this time I wouldn't advise you to go at the needles from the top (a lot of work and it requires another syncing) and I say this because plugs #3 and #4 seem to have the right colour. Also I'd check the little airintake holes in the carbs mouth are really open (at the left in the pic). Not very likely they're blocked if you have an airfilter, so first concentrate on the right fuel level of carb #1 and #2 and verify chokeflaps are not hindered in opening up.

[strynboen]

get those flot heights thekked once more..think it flots 2 carbs...the exh systen kleanes up itself...just ride 50 km..and it burn total dry and klean..like the rest of the engine..its just all this start tryes and short rum...it fills the engine vith sooth kondens vater and unburned oil...as soom yoy get all cylenders firing...give it a long ride to dry the vhole engine..all the used sparkplugs cab be glass blasted  and dryed in a oven..and then thekket by a megger(heighvolt ) for internal shorts...and the  reused..ogten they are drovned and shorted bu sod..kleaning and drying vil bring them back..

[DaveBarbier]

I'd also move on to doing the clear tube test. If you get new jets, definitely get Keihin, assuming they're still available.

It's possible you're rich across the board but have air leaks in 3&4 carb boots leaning out the mixture.

When ultrasonically cleaning the carbs, are you removing the jets and emulsion tubes?

Also, not knowing what needle setting you're on is limiting. Who knows what the PO did. On my 550 the PO drilled out the pilots from a 42 to about 90 which obviously screwed things up.

Since the aftermarket jets manufacturers typically have bad QC, you can verify the size of the hole. The hole in a size 40 jet will measure out to .40mm. You can take wires from different wire brushes, measure them with digital calipers and use them as feeler gauges.

[TwoTired]

The immediate problem is the soot on the spark plugs.  Soot is carbon and conductive.  When the center electrode insulator is coated with carbon, it shunts off the spark energy before it can jump the gap.  This makes the cylinder fire erratically.   Two options, replace with new plugs while you find the true source of the sooting up issue, clean the plugs with a blow torch, or swap them with the cylinders that are making clean plugs.

Have you done a compression check?  They can't work evenly across the bank if the compression is down on cylinders.
Same is true with the valve clearances and lift for each cylinder.
All the above issues can make the cylinders fire unevenly.  So can spark and carburetion. But, these latter can't help with mechanical issues.

If you can lay connected, clean plugs on the engine and see spark at each cylinder position, you can move on to carburetion.

Must start the carburetion investigation with verification that the fuel levels are correct in the float chambers.  Then that the jet orifices and adjustments are of the same dimension across the bank.  Are all brass parts original or Keihin? 

The upshot is that is you have 4 cylinders that aren't working the same and they should.  You cannot apply the same cure to each cylinder and expect it to behave properly.  You have to find out what is different among them.  Correct that, and them tune them all for correct mixtures.
Be aware, that during the process, a sooted up spark plug can impede proper running, even after you corrected the mixtures.  So, you will have to review that condition while make your changes.

Cheers,

[minimo]

Thanks, guys.

The carbs do have a mix and match of both original and aftermarket parts. From this kit [http://4into1.com/set-of-4-deluxe-carburetor-repair-kits-honda-cb400f-1975-1977/] I used the slow jets size 40 and the main jets size 75. I did not use the rest of the brass parts. Btw, I did also remove and clean out the tiny holes in the original emulsion tubes with thin musical wire. I decided upon using the slow jets because I thought it would alleviate the idling issues. And I used the aftermarket mains because I found that they were not all consistent numbers when I first cracked them open. They went as follows:

#1 - 80
#2 - 80
#3 - 75
#4 - 80

Though the stamping on these are faded, there was no mistake that I saw they were a mix of 80 and a 75. So, I decided I’d throw in all aftermarket 75. However, I realize as I’ve read in other posts that this can introduce the issue of the needle profile and its taper can alter the way that works with some aftermarket mains. Would this be anything to consider?

Also, the air leak assumption might me on to something. I did have my carb sync tool plugged into each of the inlets and though I did get somewhat even readings across the board, whenever I’d blip the throttle I noticed the readings would suck back first before moving up which would indicate some drawing of air. I wonder if it’s the o-rings on the ends of my carb sync brass tubes? Anyway, I’ll get the screws back in there and inspect around the boots to make sure I didn’t make any new cracks - it all looked in good condition before.

I will check on spark across all plugs doing the side engine test. As for compression, I know that I’m getting it on #4 because I would stick my thumb over the spark plug hole and feel the waft of air to find TDC during my valve checks and adjustments. And #4 cylinder happens to be not firing so that’s strange. Meanwhile, I’ll check on the other cylinders to be sure.

Anyone here out in the LA area who is good at investigating this stuff would be up for wrenching around in Glendale a bit? I have Charlie’s Place down the street. I might have to roll this bad boy over to him.



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[minimo]

Here are the float heights I got using the clear tube test. These were taken before the last start attempt:




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[Deltarider]

After seeing your pics, I have to ask you once more, are you sure chokeflaps function undisturbed, also in situ? If chokeflaps #1 + #2 do not fully open, that could well explain the sooted plugs.

[minimo]

I did bench-sync those flaps

[strynboen]

you have to heigh fuel level..if some jets also is Loose the fuel vill sump the vhole carburettor..but try to start the engine vith closed fuel tap..and fresh plugs..or heat them all up use a gas burner..it vill help them burn dry..and blow kompressed air dovn through the plug holes..so all is relative dry..and klean..and then try to start the engine..and hold it going..and turn the fuel on..and see if it help

[Deltarider]

I did bench-sync those flaps

Yes, that's fine but I'd also check if choke flaps return to full open again, after they've been closed for a cold start.

..but try to start the engine vith closed fuel tap...and hold it going..and turn the fuel on..and see if it help

Good tip from Strynboen.

[minimo]

Ok. Will try that. Thanks, strynboen!


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[minimo]

Definitely the best results yet. It also appears that we got fire across all cylinders that time.
Pulled the plugs and I can see that 3-4 had sign of slight wetness but not wet-wet like before. Should I back out the air-mix screw say another 1/4 turn on 3-4?


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[minimo]

So maybe I spoke again too soon. We are back to sooty black on 1-2 and wet-wet on 3-4...

It seems to go in that odd sequence of 1-2 and 3-4. I’d feel better if it were 1-4 and 2-3. But i think this is leaning more toward a carb issue, huh fellas?

It also seemed that the idle ran better when I shut the petcock off, almost as thought it was acted well not having that backend pressure of fuel, if that makes any sense


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[minimo]

I feel like I would rather have the case of fuel overflowing than the problem that I am having right now - at least then there’s a physical sense of, ok, this is too much fuel.


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[minimo]

Or could it be that I am running my fuel line too high? Would this have anything to do with forcing more fuel into these carbs?



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