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Discussion Starter #1
The problem is, my motor (Knucklehead, new construction) keeps fouling plugs. Motor details are as follows:

Displacement: 93”
Top End: Flathead Power
Bottom End: S&S (1936-47 Knucklehead)
Carburetor: S&S Super “E” (Shorty)
Fuel: 94 Octane
Plugs: NGK P/N BPR5ES or Champion RN12YC
Exhaust: Stock 1936-40 Knucklehead (Flash Gordon Muffler)
Ignition: Crane HI-4 Dual Fire Ignition (8-1100)
Starter: Kick

After a dozen or so kicks the motor starts and idles fine, when I blip the throttle I get a little black smoke out of the tailpipe. The motor has about 80 miles on it and fouls plugs every 10 miles or so. When I remove the plugs their sooty (flat black), not oily.

In the process of setting up the motor, I’ve made the following adjustments:

Advanced Timing: 32 degrees BTDC @ 2400 RPM’s
Air Fuel Mixture: Adjusted per the S&S Instruction Sheet
Ignition Settings: Set on Race Mode not W/VOES (OEM)

One area where I thought the problem could be was in the exhaust, specifically the muffler. Thinking the muffler may be too restrictive, I removed the baffling, however, I left the fish tail (Flash Gordon) tip in place. Removing the baffling helped but the opening at the end of the muffler is still very narrow. Can a restrictive muffler cause plugs to foul?

If it’s not the exhaust causing the problem what else can it be?

Any help you can provide would be greatly appreciated.

Thanks
 

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Shithead
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I run a shovelhead with S&S Super E. I don't think the muffler is the issue, I think it's carb setup.

Sounds to me like you are too rich all the way through. What jet sizes are you running ?

A dozen kicks sounds like a lot to me. Is that with full enricher on ?

The black smoke on blipping the throttle is too much accelerator pump, I would think. How many turns out do you have it set to ? Personally I initially set the pump screw in the garage by coming out until I get a little black smoke blipping it, and then go back in just far enough to get rid of the smoke. But the only real way is to ride with a screwdriver. You need to have enough pump on that it doesn't stumble when you open the throttle, but not much more.

Hopefully someone who knows more than I will pick this up :clap:
 

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i think Pete is on the money with the pump. if i remember correctly the carb acc pump is set all the way out and needs to be dailed in to get it to clean up.
i'd say turn the pump almost all the way in and adjust it out from there. the jets that came in it should be fine with that motor.
 

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shovel13 said:
i think Pete is on the money with the pump. if i remember correctly the carb acc pump is set all the way out and needs to be dailed in to get it to clean up.
i'd say turn the pump almost all the way in and adjust it out from there. the jets that came in it should be fine with that motor.

Yep, sure sounds like Pete and Mr. Shovel13 are right Way, way too rich.
 

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Discussion Starter #5
Thanks for the help Guys.

It sounds like I need to be looking at my accelerator pump setting. I never adjusted this setting so I checked the S&S spec. sheet and it stated "During assembly, S&S sets screw for maximum volume to aid during initial start-up after installation".

Thanks again for all of your help.
 

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Shithead
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That's right. They all vary a bit, but you should find something more like a couple turns out from the stop will be better.

If you start the bike as it is, then turn the screw all the way in (gently - it's not hard to damage it, you just want to go fingertip closed, no force), then you can blip it a bit at rest. It'll stumble. Just a little blip, then you just keep opening the screw out 1/8th of a turn or so at a time, until it will blip without stumbling at a standstill.

Then you take your screwdriver, and ride. You should find the screw will still want to come out some more because the extra riding load needs more fuel. Just keep stopping at some convenient place and taking it out another 1/8th at a time until it accelerates smooth without stumbling. If you get black smoke, you've gone too far. Hopefully, there is a sweet spot in between :)

Sorry if I'm trying to teach my granny how to suck eggs, but it pays also to remember that the S&S does not like to have the throttle snapped wide open, it likes a smooth and progressive roll-on better.

It's not hard to confuse the effects of accelerator pump settings with snapping the throttle open too aggressively, and spend hours chasing a supposed problem when all you have is incorrect operating procedure (don't ask how I know :D )

Also, you are looking for the transition between the idle and the intermediate circuits, which is where the pump operates. If you open the throttle too wide, there's a tendency for the main circuit to tip in and confuse things.

Best of luck !drunk!
 

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petelogan said:
Sorry if I'm trying to teach my granny how to suck eggs, but it pays also to remember that the S&S does not like to have the throttle snapped wide open, it likes a smooth and progressive roll-on better.
I know most people will disagree with me, but I found that adding the Yost Power Tube to the S&S eliminates the hesitation when snapping the throttle open quickly. Mine hasn't missed a beat since I installed it last year.

Pete's correct in his diagnosis, but I have one thing to add....

I have found that using the S&S enricher too much will foul your plugs very quickly. I only use mine when it's very cold out (below freezing), and even then I only use it long enough to get the bike started. As soon as it starts, I shut the enricher. I never use it during the warmup period. Just blip the throttle until it's warm enough to keep running using the throttle lock. Set the engine speed to about 1500 rpm until it's warm enough to ride. Ever since I started doing that, I haven't fouled any plugs. Just a suggestion.... ;)
 

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Shithead
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Interesting about the Yost. I was just assuming he don't have any mods.

Mine's kitted with dual Dial-A-Jets and absolutely doesn't suffer from the "S&S Hole". Had to do some radical sh1t to the jetting and air, though. Scares the crap oughta people if I tell 'em the jetting and setup and forget to mention the Thunders :roflback:
 

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Discussion Starter #9
Petelogan,

Thanks for setup information. I'll give it a try. The only problem is riding the bike, it's a chilly 30 degrees out and I don't know about you but that's to cold for me!

ToddM,

Thanks for the suggestion. Presently my carb. has no modifications.
 

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Shithead
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Yeah, it's just below zero here now, an I ain't riding in that sh1t. Next time out will be around March. Sucks, but there ya go.

It's just Pete, mate. I'm no good at that brilliant username thing :sofa:
 

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zoomingm3 said:
Petelogan,

Thanks for setup information. I'll give it a try. The only problem is riding the bike, it's a chilly 30 degrees out and I don't know about you but that's to cold for me!

ToddM,

Thanks for the suggestion. Presently my carb. has no modifications.
My bike runs GREAT in the cold weather, especially when it dips below 20 F. I can only handle it for a couple hours, though. :)
 

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Shithead
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I hate you, you barsteward :D :D :D

I'm just too firkin old :badmood:
 

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get on over to the flathead power discussion board and post your settings.

www.flatheadpower.com

despite some of the bickering there. These guys know their old iron and alot of them are running the flatheadpower engines with similar setups and can tell you what works
 

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Shithead
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You're on my sh1tlist, too :laugh:

Actually, it's warmer here today - 39F - Now till March it's gonna be mostly subzero :blink:
 

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petelogan said:
You're on my sh1tlist, too :laugh:

Actually, it's warmer here today - 39F - Now till March it's gonna be mostly subzero :blink:
If I'm on your list, that makes it unanimous. Ha.

As to temperatures. Look at it this way, Pete. Everybody's got to be somewhere. And, I might add, as we get older, it's really nice to be anywhere! :)
 

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Shithead
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Got that right, guys :D

Like my old man used to say - "Any one you walk away from is a good one"

:D
 

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fouled plugs

zoomingm3 said:
The problem is, my motor (Knucklehead, new construction) keeps fouling plugs. Motor details are as follows:

Displacement: 93”
Top End: Flathead Power
Bottom End: S&S (1936-47 Knucklehead)
Carburetor: S&S Super “E” (Shorty)
Fuel: 94 Octane
Plugs: NGK P/N BPR5ES or Champion RN12YC
Exhaust: Stock 1936-40 Knucklehead (Flash Gordon Muffler)
Ignition: Crane HI-4 Dual Fire Ignition (8-1100)
Starter: Kick

After a dozen or so kicks the motor starts and idles fine, when I blip the throttle I get a little black smoke out of the tailpipe. The motor has about 80 miles on it and fouls plugs every 10 miles or so. When I remove the plugs their sooty (flat black), not oily.

In the process of setting up the motor, I’ve made the following adjustments:

Advanced Timing: 32 degrees BTDC @ 2400 RPM’s
Air Fuel Mixture: Adjusted per the S&S Instruction Sheet
Ignition Settings: Set on Race Mode not W/VOES (OEM)

One area where I thought the problem could be was in the exhaust, specifically the muffler. Thinking the muffler may be too restrictive, I removed the baffling, however, I left the fish tail (Flash Gordon) tip in place. Removing the baffling helped but the opening at the end of the muffler is still very narrow. Can a restrictive muffler cause plugs to foul?

If it’s not the exhaust causing the problem what else can it be?

Any help you can provide would be greatly appreciated.

Thanks
Zoom,

As a dyno owner I have seen this a few times...Iron motors can not be run as lean as alminum ( evo & tc) ...but in addition to accel pump as many have said, I feel your pilot jet could be 2-3 sizes to large.....
Also there is no reason in this day and age not to get it dialed in on a dyno...dont know about your area but I get $110 to run and jet a carbed bike it only takes about 30 min to a carbed bike :duh?:

Good Luck

Steve The Dyno Guy :cheers:
 

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I know some of you might want to hear this, but I had S&S L series , E series, always a friggin pain to get right, switched to a Mikuni, awesome, don't have to roll the throttle, can crack it like a whip and there's no hesitation, try one you'll love it.
 
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