Carb woes

Accelerator pump issues

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zman
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Carb woes

#1

Post by zman »

I have a 1973 FLH mostly stock. I'm running an S&S Super E carb and I switched to an electronic ignition. The bike runs good until on my way home the bike started missing and felt like I lost a cylinder. When I got home a quick compression check reveled equal pressure in the cylinders. The bike starts right up and idles normally. But when I give her some throttle she begins to cutout and bog. I swapped plugs and wires. No change. Next was coil. No help. I even swapped out the electronic ignition. No joy. Then I noticed the accelerator pump wasn't spraying fuel. It was spitting and gurgling gas. I pulled the bowl and everything looked ok. Has anyone experienced an accelerator pump going bad? Any easy fixes or adjustments would be appreciated.
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Re: Carb woes

#2

Post by RooDog »

That carb should run pretty well even without an accelerator pump, or a main jet for that matter.
The accel pump diaphragm is the same as Harley part # 27361-76.
Check your main jet to see if it fell out of the emulation tube. The bike will run without it up to about 4000 RPM. at which point it will start breaking up.
....RooDog....
zman
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Re: Carb woes

#3

Post by zman »

Thanks RooDog, I checked and the main jet is still on. That did happen to an old Triumph I had back in the seventies. It ran ok on the city streets but wouldn't go on the highway. I found the main jet in the bottom of the bowl. Anyways I ordered a diaphragm for the S&S. Thanks for the part number. It is the same on a Keihin.
RooDog
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Re: Carb woes

#4

Post by RooDog »

zman wrote: Thu Jun 30, 2022 6:46 pm a diaphragm for the S&S. Thanks for the part number. It is the same on a Keihin.
That is correct...
I had the same thing happen on my '68 FL with a 44mm Mikuni....
Mongrel505558
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Re: Carb woes

#5

Post by Mongrel505558 »

The Super E has an O-ring near the tip of the main jet where it pokes into the venturi. When that goes south the venturi pulls gas around the main jet and ruins your high RPM performance with way too much gas. As for the accel pump, if I remember correctly the Super E has a tiny check ball that sits in a counterbore (with O-rings) between the bowl and the diaphragm cover. If that's hung up or otherwise not functioning correctly it would affect the operation of the pump. The ball lets the volume under the diaphragm fill with gas for the next squirt, and is pushed shut from pressure when the diaphragm is rapidly compressed so the gas goes out the nozzle instead of back into the float bowl when you whack the throttle. But as RooDog said, the carb should work fine without the accelerator pump unless you really quickly open the throttle. The Super B has no pump, and plenty of people, including myself, have no problem with rideability with that carb.
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Re: Carb woes

#6

Post by RooDog »

I noticed the little blue O-rig on the main discharge nozzle is missing on the G on my '68. I scored one from Spider, but have yet to install it, I did observe a blubber as I cranked up the Rs one time recently. I suppose I should install the blue O-ring and retest, no?
Mongrel505558
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Re: Carb woes

#7

Post by Mongrel505558 »

RooDog wrote: Thu Jun 30, 2022 7:55 pm I noticed the little blue O-rig on the main discharge nozzle is missing on the G on my '68. I scored one from Spider, but have yet to install it, I did observe a blubber as I cranked up the Rs one time recently. I suppose I should install the blue O-ring and retest, no?
With a Super E I've actually observed a lot of extra gas being sucked through the carb from around the main jet when I revved the motor. Turns out the O-ring was toast and a new one cured that issue. Oh yeah, the O-ring has to be blue for it to work (yeah, ok).
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Re: Carb woes

#8

Post by RooDog »

Mongrel505558 wrote: Fri Jul 01, 2022 1:02 am
RooDog wrote: Thu Jun 30, 2022 7:55 pm I noticed the little blue O-rig on the main discharge nozzle is missing on the G on my '68. I scored one from Spider, but have yet to install it, I did observe a blubber as I cranked up the Rs one time recently. I suppose I should install the blue O-ring and retest, no?
With a Super E I've actually observed a lot of extra gas being sucked through the carb from around the main jet when I revved the motor. Turns out the O-ring was toast and a new one cured that issue. Oh yeah, the O-ring has to be blue for it to work (yeah, ok).
They are blue from $&$...and that can't be wrong.... LOL..
Mongrel505558
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Re: Carb woes

#9

Post by Mongrel505558 »

RooDog wrote: Fri Jul 01, 2022 2:55 am
Mongrel505558 wrote: Fri Jul 01, 2022 1:02 am
RooDog wrote: Thu Jun 30, 2022 7:55 pm I noticed the little blue O-rig on the main discharge nozzle is missing on the G on my '68. I scored one from Spider, but have yet to install it, I did observe a blubber as I cranked up the Rs one time recently. I suppose I should install the blue O-ring and retest, no?
With a Super E I've actually observed a lot of extra gas being sucked through the carb from around the main jet when I revved the motor. Turns out the O-ring was toast and a new one cured that issue. Oh yeah, the O-ring has to be blue for it to work (yeah, ok).
They are blue from $&$...and that can't be wrong.... LOL..
My terminology isn't quite correct. When I say gas sucked around the main jet I mean the discharge nozzle that the main jet screws into the bottom of. You obviously know what I meant.
RooDog
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Re: Carb woes

#10

Post by RooDog »

I wonder if the blue O-rings are special.
Modern automotive air conditioning with R 134 refrigerant specifies green O-rings. Black O-rings can be of several different materials like buna-n, viton, or other unidentified mystery "rubbers". So, I wonder if the blue ones $&$ uses are special. Does anybody know?
Mongrel505558
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Re: Carb woes

#11

Post by Mongrel505558 »

RooDog wrote: Fri Jul 01, 2022 3:26 pm I wonder if the blue O-rings are special.
Modern automotive air conditioning with R 134 refrigerant specifies green O-rings. Black O-rings can be of several different materials like buna-n, viton, or other unidentified mystery "rubbers". So, I wonder if the blue ones $&$ uses are special. Does anybody know?
In case anyone cares, I just looked it up on the internet. There apparently is, in fact, a color code for O-rings:
https://www.globaloring.com/oring-colors/

Blue = fluorosilicone
Black = NBR/Viton/FFKM/EPDM/Neoprene
Brown = Viton
Clear = Urethane
Green = Viton
Red = Silicone
etc.

Maybe blue isn't the best choice anymore. The S&S O-rings have been blue for as long as I can remember. Now with all the ethanol added to gasoline there may be a better choice, although fluorosilicone is rated "Good for both static and dynamic seals" for use with ethanol.
RooDog
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Re: Carb woes

#12

Post by RooDog »

The Pingel valves use the brown, looks tan to me, O-rings if that's a clue as to fuel resistance.....
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Re: Carb woes

#13

Post by nifty »

These days there are a zillion specialised o-ring materials
Ethanol gasoline, both chemical resistances have to be considered
In general industry, brown Viton is considered E85 safe (but not safe for brake fluid)
Learn more here
https://www.pegasusautoracing.com/docum ... =TECH00147
https://blog.parker.com/site/usa/detail ... ssembly-us
Nifty
zman
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Re: Carb woes

#14

Post by zman »

Ok, I got a new diaphragm from JP cycles in the mail today. I installed it and started up the bike. With the filter cover off and looking in the venturi I can see the ejector nozzle spraying gas. (I set the accelerator pump adjustment screw CCW one and a half turns). But when I move the throttle gas sprays out the ejector and I see gas also splashing out of the discharge tube. Did I install the diaphragm correctly? I'm also not sure about the little blue Oring that sits on the ejector nozzle. When I set it on the ejector tube does it stay below the bowl gasket? Or does it fit above the gasket? When I roll on the gas the engine immediately wants to bog out. Way too much fuel at off idle. Ok I'm back. I closed the accelerator pump and started the bike. It idles but when I go off idle fuel splashes out of the main discharge tube. The main jet circuit shouldn't come in until above 2000 rpm. What would cause fuel spilling into the venturi from the discharge tube right off idle?
RooDog
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Re: Carb woes

#15

Post by RooDog »

Without going out back, removing the breather cover, starting my scooter, and peeping down the throat of a running carby, I'm gonna say that that is what it's supposed to do.
The main jet is a restriction, not a feeder, it only serves to limit the amount of fuel delivered at higher RPM, so as discussed earlier, the bike will run without the MJ because it is not pulling a lot, but some, fuel through the main delivery circuits. But without that jet's restriction the engine will go way rich at higher Rs. Some fuel/alcohol race engines I have known ran without any main jets at all. They needed all the fuel they could get.....
Follow $&$'s tuning guide, and you should be OK....
....RooDog....
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