Author Topic: Weird intermittent spark  (Read 6445 times)

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Offline Sdsbassist

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Weird intermittent spark
« on: March 18, 2016, 03:32:38 PM »
Found cyl 1 pipe was cold. When I hooked up a timing light to the wore, found that it was sparking, but inconsistent. 4 looks fine. Check connections?

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Gene

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Re: Weird intermittent spark
« Reply #1 on: March 18, 2016, 03:35:48 PM »
Replace the plug cap?  Clip back about 1/4 of the wire for a good connection.  Cheap, easy check.
*1973 CB750K3 (Bow)

Offline Stev-o

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Re: Weird intermittent spark
« Reply #2 on: March 18, 2016, 03:56:13 PM »
Did you replace plugs, points, condensers & caps?

If no, C'mon Man!
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #3 on: March 18, 2016, 04:08:48 PM »
It's just the one cyl which should Elim what steve just said. I tried two plugs in cyl 1 plug boot and it was arcing more widely than the others. Bad cap?

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #4 on: March 18, 2016, 05:05:00 PM »
The other issue could be gas I'm guessing

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #5 on: March 18, 2016, 05:16:35 PM »
Just pulled plugs and it's wet....flooded?

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline HondaMan

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Re: Weird intermittent spark
« Reply #6 on: March 18, 2016, 06:26:18 PM »
Just pulled plugs and it's wet....flooded?

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Just wet, from not firing.. ;)
See SOHC4shop.com for info about the gadgets I make for these bikes.

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Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
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Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #7 on: March 18, 2016, 06:28:42 PM »
So would the weird arching cause it to not even spark when it actually in the cylinder.

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #8 on: March 18, 2016, 06:31:37 PM »
I'm considering plugging wire 1 to 4, and 4 to one to see if that makes any change. Would narrow it down to wires or carbs?

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« Last Edit: March 18, 2016, 06:43:22 PM by Sdsbassist »
Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #9 on: March 18, 2016, 06:42:49 PM »
here is a bad interpretation of what I see what I ground plugs to head to test them. #1 shoots the spark more randomnly then the others.
Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Stev-o

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Re: Weird intermittent spark
« Reply #10 on: March 18, 2016, 07:14:57 PM »
Did you replace plugs, points, condensers & caps?

If you are not going to give it a proper tune up, you are just going to chase your tail.
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #11 on: March 18, 2016, 07:15:46 PM »
No.

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #12 on: March 18, 2016, 07:55:24 PM »
Are any of you suspecting coals?

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Stev-o

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Re: Weird intermittent spark
« Reply #13 on: March 18, 2016, 07:57:16 PM »
Are any of you suspecting coals?



I would bet it's not coals
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #14 on: March 18, 2016, 07:57:54 PM »
I'm cool with that. Does honda carry boots? Any better value or brand?

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #15 on: March 18, 2016, 07:58:31 PM »
Are any of you suspecting coals?



I would bet it's not coals
It's gonna be something simple. She sounded good on 3 cyl. She will sound amazing on 4

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #16 on: March 18, 2016, 07:59:26 PM »
Yes and I really wanna try but got 4 kids sleeping. Before lunch tomorrow

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #17 on: March 18, 2016, 08:01:37 PM »
Don't do this to me bro!!

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #18 on: March 18, 2016, 08:04:21 PM »
I closed that up for the night. But that post was definitely the best ever.

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Stev-o

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'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #20 on: March 19, 2016, 11:57:19 AM »
So put in a different plug, swapped the 1 and 4s and started for 2 min. 1 pipe still cold cold cold. Still damp with a bit of fuel smell.

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #21 on: March 19, 2016, 12:10:21 PM »
I've swapped caps too. Measurements? What type of measurements can I get you

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Deltarider

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Re: Weird intermittent spark
« Reply #22 on: March 19, 2016, 12:12:05 PM »
Quote
Resistance of each cap measured with a meter. While you're at it, measure coils too please.
+1
BTW, what bike are we talking about?
Can you inform us if you've done other things (like maintenance or 'repairs') before this started?
The last thing you did, is often the cause.
 
« Last Edit: March 19, 2016, 12:15:54 PM by Deltarider »
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Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #23 on: March 19, 2016, 12:13:06 PM »
Well this was my first start up for bike. Cleaned carbs, bench sync, gapped plugs at .26,

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"

Offline Sdsbassist

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Re: Weird intermittent spark
« Reply #24 on: March 19, 2016, 12:15:20 PM »
Sounds good. Guessing my manual will give me details on the proc?

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Gus, Austin, MN.
Current Bike:  75 750F

Past bikes: 76 750K - "Iowa Blue",78 750K Craigslist find - "Black Beth;" 77 CB750K Basketcase, with a 75K engine; 1970 Cb750 K1, "Rosa Luxembourg"
74 cb750, 75 cb550, 77 kawa 650, 81 virago 750, 83 virago 920, 80 Honda Twinstar 200, 71 Honda CT70, 1971 Honda CB750 Rat Project "Black Dahlia Bitsa"