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Author Topic: Advice on my Harley Shovelhead?  (Read 1130 times)

Offline BartusCompater

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Advice on my Harley Shovelhead?
« on: May 15, 2016, 07:44:28 PM »
Hey folks,

I've also made a post on the Harley forums, but there are some very knowledgeable and reliable folks here on the nighthawk forum that I'd love to get 2 cents from on an issue I'm having with my other bike, a 1979 Harley Shovelhead.  :shg:

My Dad and I fixed it up last summer, and it was in tip top shape. He says that he has been starting it up every once and a while since then to keep liquids circulating. In any case, I went to take it for a ride today and it was struggling to run without the choke and a healthy bit of throttle. After letting it run for a good long while, it finally got to the point where it could idle on its own without choke, but it sounded really weak AND I noticed something a little worrisome--

One of the pipes was spitting out light colored smoke and thin liquid (I first thought oil, but now believe to be fuel) was coming out. Only on the one pipe.

The bike would bog down and die under any kind of load until we'd had it idling for a good 15 minutes. Then when I took it out to the street and fully accelerated, it began to backfire like a machine gun--with bursts of power on each backfire.

I'm suspecting that fuel in one of the cylinders isn't being properly ignited, but wondering what you all think. I'm not an experienced Harley guy. My Dad tells me that he tipped it over in the garage while trying to move it earlier in he year... and I'm wondering if that may have led to an exhaust leak & improper mixture. What do y'all think?

Thanks for your help.
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Offline SoloVoyage

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Re: Advice on my Harley Shovelhead?
« Reply #1 on: May 15, 2016, 08:41:21 PM »
I'd check the plugs/plug wires for a start. Sure sounds like it's not firing on that cylinder.

Offline RJ CB650

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Re: Advice on my Harley Shovelhead?
« Reply #2 on: May 18, 2016, 05:26:53 PM »
A bit late, but definitely sounds like a plug not firing right.  Easy test is start bike, and spray each pipe at head with a mist of water from spray bottle.  If one sizzles and one doesnt, that is your cylinder.

On my bikes, it comes up once and a while.  Plug fouls up a lil from short rich running and idle.  Pulling out and testing spark might have spark, but it should be crisp and even directly across electrodes.

Offline BartusCompater

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Re: Advice on my Harley Shovelhead?
« Reply #3 on: May 18, 2016, 11:56:16 PM »
I think you both may have hit the nail on the head.


The folks at the Harley forum advised stuck float bowl, but my Dad called me to report that he replaced the spark plugs and all seems to be well. We'll see when I get a chance to ride back up there and take a look at it!
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Offline SoloVoyage

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Re: Advice on my Harley Shovelhead?
« Reply #4 on: May 19, 2016, 12:00:58 AM »
Sure sounded like a firing issue to me. Hope that was the issue and you get to ride soon! Good luck.

Offline BartusCompater

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Re: Advice on my Harley Shovelhead?
« Reply #5 on: May 20, 2016, 09:37:17 PM »
One of the plugs was all blackened up. I just rode it ~40 miles and it's better than ever with the new plugs.


Perhaps it was luck, but funny how in this case Honda folks knew better than the Harley folks when it came to diagnosing a Harley.  claugh1



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Offline SoloVoyage

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Re: Advice on my Harley Shovelhead?
« Reply #6 on: May 20, 2016, 10:52:41 PM »
One of the plugs was all blackened up. I just rode it ~40 miles and it's better than ever with the new plugs.


Perhaps it was luck, but funny how in this case Honda folks knew better than the Harley folks when it came to diagnosing a Harley.  claugh1

That cylinder is running way too rich or there's an oil problem causing it to foul. Just a matter of time before it happens again, just long enough for that plug to foul out again.... Glad you got it running though.

Offline aycaramba

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Re: Advice on my Harley Shovelhead?
« Reply #7 on: May 21, 2016, 08:43:38 AM »


Perhaps it was luck, but funny how in this case Honda folks knew better than the Harley folks when it came to diagnosing a Harley.  claugh1

An motor is a motor is a motor.  You have to ask yourself, which population of riders does the most self-wrenching?  A group whose chosen model was discontinued 16 years ago, or the group that can't throw a rock without hitting a mega - dealership that caters to casual (and often infrequent) riders.

Point being, this is a crew that has considerable experience self diagnosing probelems, partly because there is a limited number of shops that want to work on the NH.  So, we learn to do for ourselves.  It can be a pain, but it does have its advantages.

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Offline RJ CB650

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Re: Advice on my Harley Shovelhead?
« Reply #8 on: May 21, 2016, 01:37:51 PM »
If it is black black fouled, then could be the float or other issue as well causing it to flood and way overrich.  Good thing those ol engines are able to be wrenched on!

Offline BartusCompater

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Re: Advice on my Harley Shovelhead?
« Reply #9 on: May 23, 2016, 03:09:22 PM »
If it is black black fouled, then could be the float or other issue as well causing it to flood and way overrich.  Good thing those ol engines are able to be wrenched on!


It is totally black, but no deposits. Like someone just spray-painted it black. I'm curious if this explains why only one plug is affected?
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Offline SoloVoyage

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Re: Advice on my Harley Shovelhead?
« Reply #10 on: May 23, 2016, 07:48:10 PM »
If it is black black fouled, then could be the float or other issue as well causing it to flood and way overrich.  Good thing those ol engines are able to be wrenched on!


It is totally black, but no deposits. Like someone just spray-painted it black. I'm curious if this explains why only one plug is affected?

I'd say yes, it's a single cylinder issue. Was it wet or baked on blackness?

Offline RJ CB650

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Re: Advice on my Harley Shovelhead?
« Reply #11 on: May 24, 2016, 08:03:34 PM »
Ol shovel... Is single carbed correct?  I wonder if ignition or some timing is off.  Perhaps a vacuum leak on other cylinder?  Hrm hrm....  could be different causes.  Tough without having the bike.  The new plug blackening??  Could be chicken or egg.  Bad spark fould plug, then sorta chained.  Black a symptom from being flooded.

Offline BartusCompater

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Re: Advice on my Harley Shovelhead?
« Reply #12 on: May 25, 2016, 11:12:29 AM »
Yes, it's a single carb that feeds both cylinders, which is why I'm wondering how a stuck float would only affect one plug. But I don't know if it's possible that the fuel just leaks down into the front cylinder.


The spark plugs were replaced last summer, if that helps narrow things down a bit. They were pretty fresh plugs.


Folks on the Harley forum are suggesting that I take a look at the points, as well as the fuel squirter in the carb (wondering if it might be twisted toward the front cylinder and squirting more into that one --- who designed these things??)
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Offline SoloVoyage

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Re: Advice on my Harley Shovelhead?
« Reply #13 on: May 25, 2016, 06:46:27 PM »
It "could" be just as simple as a bad plug. Let's hope so.

Offline RJ CB650

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Re: Advice on my Harley Shovelhead?
« Reply #14 on: May 26, 2016, 05:33:58 PM »
Chatting with a harley guy, 79 shouldnt have points, it should be electronic ignition.  If it was converted to points, is recommended to convert back if is points.  So could be weak coil or burning oil to foul a single cylinder as well.

 

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