Topic: Colouring pipe, black plugs, no gas

[mathias2803]

Greetings from Norway! The other day I got a new stainless steel exhaust. After the bike has been warm couple of times I noticed yellow/gold colouration. I've heard this is because of running lean or tight valves? It has not turned blue, but I'm afraid it will if I run it any more. The headers get hot really quick, while rest of the pipes can stay cool for some time.
But if it's lean, should the plugs be black? Also the pipes have turned black inside. I can see that there is little fuel running through the clear filter. I have switched fuel lines several times and tried different routes, the petcock is new.
Starts quickly with full choke and open throttle. And the oil tank smells like gas.. Carbs has been rebuild with stock sizes. Stock airfilter, new boots.
In the vid you can also hear a rattling.
The bike feels very responsive and powerful when driving.
This is a 73 750 sohc

https://youtu.be/x1SAKVnxkOI



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[robvangulik]

Stainless steel always turns yellow when heated repeatedly.
Are those iridium sparkplugs?
Try normal NGK's.

[bryanj]

Stainless pipes are single skinned whilst original are double skinned so the hot gas does not contact directly the outside pipe

[mathias2803]

Stainless steel always turns yellow when heated repeatedly.
Are those iridium sparkplugs?
Try normal NGK's.

The guys at cycleX who made it told me it should not turn gold ish and that it could be a sign of the bike running lean. Is there a big difference between iridium and normal?

Anyone know what the rattling sound is?
Appreciate the time

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[robvangulik]

Rattling, what rpm is it running, it sounds really low.
Are you sure those pipes clear your front wheel when braking?

[mathias2803]

Rattling, what rpm is it running, it sounds really low.
Are you sure those pipes clear your front wheel when braking?

Yea Usually I have to adjust the idle screw because of uneven idle. Here it was adjusted really low. Nope probably not, I'm going to sell the pipes and raise the height about 1,5"inch. It's not a problem with the old pipes. Don't know if its the pipes or if its because I have lowered it

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[TwoTired]

If it is running really rich, it could be afterburn being completed in the exhaust header, which, of course would be hotter than regular exhaust.

Not sure why you chose iridium.  They are mostly for high energy ignitions, to reduce electrode wear from electrical discharge.  However, if only the tip is iridium, only half the plugs will benefit from the electrode erosion, as our SOHC4 fire one plug in positive polarity and the other in negative polarity.  For iridium to actually benefit, both the tip and the ground strap have to be iridium.

Cheers,

[calj737]

A mild correction about the coloration of your pipes. ALL stainless will turn a color when heated, the actual color being a "thermometer" of sorts. The straw yellow tint is the presence of heat and it will remain unless you clean the pipe periodically. The hotter the pipes run, they will turn blue. That means your exhaust gas is somewhere above 600*F. That is not good as its too hot for your bike to producing.

If the straw yellow color doesn't change, then you have absolutely nothing to worry about, live with it, enjoy it, and be proud that the exhaust temp is right where its supposed to be, below 500*.

Your pipes will not discolor equally along their length. The exhaust gas cools during travel, so the farther away from the head, the cooler it becomes. Stainless actually absorbs that heat depriving the gas from its own energy in a way. Its sensible to wipe the pipes down with Acetone after handling them or working on your bike. Any oil or grease left on them will get badly baked on once the pipe gets hot.

[mathias2803]

Some say lean and some say rich. I will have to take a closer look to find out what is the case.
I'm not sure about the plugs, I will check if they are iridium when I'm home.

I guess I can use a distance thermometer to check how hot the pipes get.

Will be checking the floats and the idle valves and change the oil since it's gas in it

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[ekpent]

 Your black sooty plug is not showing signs of being lean.

[mathias2803]

Your black sooty plug is not showing signs of being lean.

I know, that's why I'm confused since someone told me different. That it was rich was my first impression. When the bike is hot it's riding really well.

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[WhyNot2]

My plugs look the same.

Have real bad gassy smell also. Seems I have more work ahead of me.

[mathias2803]

My plugs look the same.

Have real bad gassy smell also. Seems I have more work ahead of me.

I'm gonna check the float needle and be sure to turn off the petcock. Also definitely change the oil

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[HondaMan]

When unburned fuel is spit out to the pipes, it continues to burn. Rich mixtures make this situation worse. It is not uncommon for rich exhaust to discolor pipes: is is usually the primary cause of this discoloration.

A question for you: in the picture, the plug gap looks very wide. Is it more than 0.028" gap? If so, the plug is experiencing a very short spark, which can create symptoms that mimic a too-rich fuel condition. When the gap is too large, the spark only appears for a portion of the coil discharge: in the OEM coil there are 5 spark excursions back-and-forth between the electrodes at 0.028" gap, and only 3 excursions at 0.035". Note: this is not to be confused with "multiple spark" systems: instead, once the plasma sets up from the first spark, it echos back-and-forth between the electrodes until the coil discharges fully enough to stop it. If the gap is too big, the spark duration suffers and fuel is left unburned.

[mathias2803]

When unburned fuel is spit out to the pipes, it continues to burn. Rich mixtures make this situation worse. It is not uncommon for rich exhaust to discolor pipes: is is usually the primary cause of this discoloration.

A question for you: in the picture, the plug gap looks very wide. Is it more than 0.028" gap? If so, the plug is experiencing a very short spark, which can create symptoms that mimic a too-rich fuel condition. When the gap is too large, the spark only appears for a portion of the coil discharge: in the OEM coil there are 5 spark excursions back-and-forth between the electrodes at 0.028" gap, and only 3 excursions at 0.035". Note: this is not to be confused with "multiple spark" systems: instead, once the plasma sets up from the first spark, it echos back-and-forth between the electrodes until the coil discharges fully enough to stop it. If the gap is too big, the spark duration suffers and fuel is left unburned.

I'm not sure, I will have to measure. For information these are iridium plugs and I have 5ohm dyna coils. Aftermarket exhaust and orginal air box with foam filter if I remember correctly

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[Tracksnblades1]

Are your iridium NGK spark plugs Resistor type. A lot of NGK iridium plugs are.
Read HondaMan's post regarding NGK resistor type spark plug boots. Your spark plug boots can have 5k-10k ohms already, depending on which ones you have. Defective ones, more. Running resistor spark plugs series the resistance (adds).

I'm guessing your running DR8EIX plugs...?

[mathias2803]

Are your iridium NGK spark plugs Resistor type. A lot of NGK iridium plugs are.
Read HondaMan's post regarding NGK resistor type spark plug boots. Your spark plug boots can have 5k-10k ohms already, depending on which ones you have. Defective ones, more. Running resistor spark plugs series the resistance (adds).

I'm guessing your running DR8EIX plugs...?

Yes you are correct about the spark plug type. The boots are NGK

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[Tracksnblades1]

In addition to your possible carburetor and float woes. Make sure your points, timing, valve lash are within spec.

Check out HondaMan's writings of resistance in the ignition coils secondary circuit (spark plug circuit).
Honda used different resistor values in the spark plug caps over the years. Some have recommended against using resistor type plugs with resistor spark plug caps, adding series resistance. NGK may still manufacture 0ohm spark plug caps but I haven't checked.

I don't think NGK DR8EIX are the double iridium type. But, I'm not sure.
Attached are pictures of Bosch double platinum and double iridium. Purposely manufactured for the wasted spark ignition's reversed spark polarity of the running pair.

[mathias2803]

The plug caps are the resistor type, I switched to denso U plugs. Did not make any difference. The timing has been set once, but can check it again.
After oil change I'm having struggle starting it

[HondaMan]

In addition to your possible carburetor and float woes. Make sure your points, timing, valve lash are within spec.

Check out HondaMan's writings of resistance in the ignition coils secondary circuit (spark plug circuit).
Honda used different resistor values in the spark plug caps over the years. Some have recommended against using resistor type plugs with resistor spark plug caps, adding series resistance. NGK may still manufacture 0ohm spark plug caps but I haven't checked.

I don't think NGK DR8EIX are the double iridium type. But, I'm not sure.
Attached are pictures of Bosch double platinum and double iridium. Purposely manufactured for the wasted spark ignition's reversed spark polarity of the running pair.

Wow, this is some kind of....stuff...
When the coil discharges, it breaks down in an AC (alternating current) oscillation. If they can still be found, the entire series where I developed the Transistor Ignition here shows the oscilloscope waveforms of the discharge activity. IIRC, there were 7-10 back-and-forth cycles with the Honda coils and 5-7 (depending on engine speed) with the Dyna 3-ohm coils I used in those tests, and those pictures are all posted here for the world to see. Platinum? Iridium? The only difference the metals make regards erosion wear. The tinier 'tips' where the precious metal(s) are built up provide a smaller target site for the electrons to build up and jump from, to the opposite polarity: this technique is called "improving the electron field density" and is widely used in electronic systems. This is why the original "fine wire" plugs were so successful in the 1970s, but they wore quickly: when they reappeared, it was with...platinum tips to reduce wear and increase life.

[mathias2803]

Spark Is all over the place and not between the points on the plugs. Tried with denso and NGK iridium with same results. Not sure if this means anything

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[PeWe]

Try std plugs, NGK D8EA or Denso equal.
My K6 with Dyna 5 ohm coils did not like iridium plugs. Ran colder. I usually set plugs to 0.7mm, I'll test 0.6mm next time.

[mathias2803]

Try std plugs, NGK D8EA or Denso equal.
My K6 with Dyna 5 ohm coils did not like iridium plugs. Ran colder. I usually set plugs to 0.7mm, I'll test 0.6mm next time.

Just said I tried denso without any difference.  The plugs are not the problem. But thanks for sharing.

Are you using NGK caps with resistors with the 5ohm coils?

Anyone know how I can measure the resistance in the caps?

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[TwoTired]

Cap resistance is measured with them unscrewed from the wire and probes inserted in each end.  Infinity measurement means the cap is open and has an extra gap to jump inside, requiring higher voltage than might be available.  Should be replaced, if so.

Resistor plugs usually have 5K Ω resistance. The resistors have a 10-20% tolerance range and function is maintained within that range. You probably don't want more the 10K total for each spark path.  The cap and plug resistance would add directly.  Most 750s have about 5KΩ resistance in each spark path to electrode.  550's will work fine with 10K resistance coil to electrode.  All mine have 10KΩ plug caps, with the Hotter D7ES plugs.  Colder D8 plugs probably are fine with 5KΩ caps *or* 5KΩ resistor plugs with stock coils.   But, the spark gap needs to be to Honda specs, too.

Have you ruled out a points and or condenser issue?  These can mess with spark, too.  Clean contacts with file, not grit that can embed in the soft metal.

Cheers,

[PeWe]

My bike(s) have Dyna 5 ohm coils, NGK 5kohm caps. copper HT wires. I have bad experience of Dyna supressed grey graphite wires.

Denso  x24es-u or NGK D8EA plugs.

TEC points and Hondaman ignition.
Running sooty black plugs can be floading floats.

Make sure ignition is OK and does not advance too early. Both mine did and have their adv springs cut 1/2 turn or slightly more.