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Old 05-13-2017, 05:39 PM   #1
slapshift68
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Default sooty front knuck plug

Hello all,
I've been trying to sort out the '47's miss(or stutter) for a couple of weeks now and have made some headway but now I'm at a loss,well,not completely,but I need some guidance.

I pressure tested with about 8lbs of air and soapy water and did indeed find leaks around the manifold at the heads and repaired them.Tested again, found a tiny one and repaired it.took it for a ride today and still have the stutter. Pulled the plugs,the rear was beautiful! the front not so much(sooty).Pressure tested again,NO LEAKS.I sprayed around EVERYTHING and all was well.

So now I need guidance. Where do I go next? Valve adjustment?

Thanks so very much in advance
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Old 05-13-2017, 06:49 PM   #2
Wisco Cal
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Default Re: sooty front knuck plug

I would start with valve adjustments because they're easy and free to be certain of. Ignition timing or maybe even plugwires next. Confirm plug gap, even.
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Old 05-13-2017, 08:45 PM   #3
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Default Re: sooty front knuck plug

thanks for the input Wise,

Timing is perfect and I replaced the coil and wires a few weeks back. Also,new points and condenser.Plugs are gapped at .25. Also tried them at .30 not a change
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Old 05-13-2017, 08:55 PM   #4
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Default Re: sooty front knuck plug

Quote:
Originally Posted by slapshift68 View Post
thanks for the input Wise,

Timing is perfect and I replaced the coil and wires a few weeks back. Also,new points and condenser.Plugs are gapped at .25. Also tried them at .30 not a change
was the problem after the tune up and parts?
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Old 05-13-2017, 09:16 PM   #5
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Default Re: sooty front knuck plug

No Sir,its been with me for awhile
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Old 05-13-2017, 09:20 PM   #6
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Default Re: sooty front knuck plug

Joe,
I did the tune up,coil,wires,points and condenser and timing adjustment to try to cure the miss.

I did have new rings and a valve job done a few months back because it had sat for 8 years and I had NO idea who did what to it before that
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Old 05-14-2017, 03:28 AM   #7
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Default Re: sooty front knuck plug

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Originally Posted by slapshift68 View Post
Joe,
I did the tune up,coil,wires,points and condenser and timing adjustment to try to cure the miss.

I did have new rings and a valve job done a few months back because it had sat for 8 years and I had NO idea who did what to it before that
When you say miss or stutter? explain it to me. I have a tiny stutter on my panhead albeit my plugs are both running spot on. Mine is a slight air leak through my linkert I'm 99% sure. Have you rebuilt your carb? Not at the manifold here I'm talking through the mixture needle seating.
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Old 05-14-2017, 06:14 AM   #8
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Default Re: sooty front knuck plug

Rhy,

The bike runs great everywhere except 0-1/4 throttle and thats only on when I let off the throttle.It's like its running out of fuel.

When I got the bike it had a super b. I pulled it and put on a cv which is what I have on my shovel as well. The cv has a 45 slow and 170 main with an adjustable needle. I've pulled it apart and put it back together countless times.I've raised jets and needles and lowered jets and needles,checked the slide diaphragm,pinched one replaced it,adjusted the float up and down etc.

One thing I did notice yesterday was a faint puff of white smoke thru the exhaust.Very faint but noticeable.
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Old 05-14-2017, 06:17 AM   #9
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Default Re: sooty front knuck plug

I should also mention that I have excellent fuel flow,the fuel line doesn't touch the heads anywhere. And thinking about it more it does show the same symptoms at higher speed but less frequently and never under load.
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Old 05-14-2017, 06:28 AM   #10
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Default Re: sooty front knuck plug

Quote:
Originally Posted by slapshift68 View Post
Rhy,

The bike runs great everywhere except 0-1/4 throttle and thats only on when I let off the throttle.It's like its running out of fuel.

When I got the bike it had a super b. I pulled it and put on a cv which is what I have on my shovel as well. The cv has a 45 slow and 170 main with an adjustable needle. I've pulled it apart and put it back together countless times.I've raised jets and needles and lowered jets and needles,checked the slide diaphragm,pinched one replaced it,adjusted the float up and down etc.

One thing I did notice yesterday was a faint puff of white smoke thru the exhaust.Very faint but noticeable.
Hey man,

White smoke to signals lean or an air leak.. white smoke though... confusing.
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Old 05-14-2017, 11:45 AM   #11
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Default Re: sooty front knuck plug

Keihin CV? did you drill the hole in the slide or install a lighter spring? Also pull and check the diaphragm for cracks. Here is some reading for you.
https://cv-performance.com/harley-cv...-tuning-issues
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Old 05-14-2017, 04:02 PM   #12
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Default Re: sooty front knuck plug

I'm thinking that one carb for two cylinders should have a close plug reading on both unless something is wrong on that particular cylinder. .Correct?
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Old 05-14-2017, 05:02 PM   #13
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Default Re: sooty front knuck plug

The slide was drilled to 7/64. I couldn't tell you about the spring.

The diaphragm has no tears at all.The thought had occurred to me to replace the spring and slide with an unmolested one but I thought along the same lines as truck as far as equal readings per one carb.

Could a drilled slide cause one cylinder to read different from the other?
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Old 05-15-2017, 02:48 AM   #14
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Default Re: sooty front knuck plug

These are instructions I got
For ULH
Worked straight out of box.Click image for larger version

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ID:	235474Click image for larger version

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Old Yesterday, 07:53 PM   #15
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Default Re: sooty front knuck plug

So I've been trying to sort this out,rear exhaust pushrod was binding slightly,adjusted it correctly.
Checked again for intake leaks,still none.

I'm at a loss now unless its carb related. And it may be but I still don't know that one cylinder would be THAT different from the other.

Suggestions?
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Old Yesterday, 09:39 PM   #16
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Default Re: sooty front knuck plug

Front intake valve guide may be worn or loose in the head. Sucking oil into the cylinder when the throttle butterfly closes and intake vacuum rises. Stutter could be due to the oil fouling the plug, and creating the sooty condition.
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Old Yesterday, 10:41 PM   #17
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Default Re: sooty front knuck plug

Quote:
Originally Posted by WhizzbangK.C. View Post
Front intake valve guide may be worn or loose in the head. Sucking oil into the cylinder when the throttle butterfly closes and intake vacuum rises. Stutter could be due to the oil fouling the plug, and creating the sooty condition.
This is what I'm thinking... sucking oil through the valve. I had the same issue, mine was a loose valve guide letting oil around it. Rear plug ok, front plug black.
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Old Today, 07:18 AM   #18
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Default Re: sooty front knuck plug

I had a problem last year with my 65 ...just like your symptoms , it felt like it was running out of gas when I let off the throttle , then it would stumble and pick up as I twisted the throttle .....long story short I was the float coming loose . Finally started leaking out the overflow when I turned on the gas , after I took off the bowl and tightened it to the arm she is running good again !
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