Gas feed problem
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4th Gear
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Gas feed problem
Hi, I have a 1990 FLHS that is giving me problems with gas flow. It is an EVO motor (standard) with an S&S carb. The gas gauge is not working, but the unit is still in place (the float). It also has the standard petcock valve in place. The symptoms are as follows. I start with a full tank of gas, set the trip odometer to 0000.0, and when I hit about 110 miles, the bike starts to buck and spit, like it's running out of gas. If I turn the petcock valve to reserve, the problem goes away, but the bike never runs smoothly while it's on reserve. I have been told to change the petcock valve out to a Pingle for better gas flow because my carb is demanding more gas. But during the first 110 miles, the bike runs fine. My thought is the float from the electronic gas gauge is somehow interfering with the gas flow when it gets to the level where the petcock valve is. (They're both on the left side). As it turns out, the amount of gas that I can put into the tank when this problem happens is only about 3 gallons. If the tank is 5 gallons, that means I still have 2 gallons (about) in the tank... well above where the reserve should be needed. If anyone has an answer, please help. Thanks, Ray
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From: Phoenix '53, '88, '09 Big Twins
The pingel is nice, but I never needed the "extra flow" on any of my evos.
Probably crud in the tank- drain as much gas as you can and remove the petcock- a funnel with a gas line to a gas can will do and keep the mess down.
once you have the petcock out, clean the screen and look for crud. You'll see that the petcock has 2 passages for gas, one is recessed and that's the RES the other is elevated about a 1/2" and that is the main
IF your tank has a bunch of loose crap and rust in it you can put in a handful of nuts and bolts and shake them around- count them going in and coming out.
You could also look at a kreem type tank liner/sealer.
Probably nothing a little cleaning won't fix.
use a little teflon tape on the threads when the petcock goes back on
It is also possible that the tank is not venting and vacuum locking- make sure the fuel line is not touching the cylinders ( so the gas can't boil inside the lines)- if you get another episode where it seems starved, try cracking the gas cap- if that changes it, you can drill the bottom of the gas cap with a 1/8" bit, you will see on the bottom a number of round casting marks about 1/8" in diameter, just drill out one of those- not too deep.
Also with a conventional carb like an S&S you can pull obstructions through the fuel lines by getting the bike to high speed and closing the choke all the way, opening the throttle all the way- the vacuum will suck anything through---BUT if you have rust in the tank you don't wanna do that!
Mike
Probably crud in the tank- drain as much gas as you can and remove the petcock- a funnel with a gas line to a gas can will do and keep the mess down.
once you have the petcock out, clean the screen and look for crud. You'll see that the petcock has 2 passages for gas, one is recessed and that's the RES the other is elevated about a 1/2" and that is the main
IF your tank has a bunch of loose crap and rust in it you can put in a handful of nuts and bolts and shake them around- count them going in and coming out.
You could also look at a kreem type tank liner/sealer.
Probably nothing a little cleaning won't fix.
use a little teflon tape on the threads when the petcock goes back on
It is also possible that the tank is not venting and vacuum locking- make sure the fuel line is not touching the cylinders ( so the gas can't boil inside the lines)- if you get another episode where it seems starved, try cracking the gas cap- if that changes it, you can drill the bottom of the gas cap with a 1/8" bit, you will see on the bottom a number of round casting marks about 1/8" in diameter, just drill out one of those- not too deep.
Also with a conventional carb like an S&S you can pull obstructions through the fuel lines by getting the bike to high speed and closing the choke all the way, opening the throttle all the way- the vacuum will suck anything through---BUT if you have rust in the tank you don't wanna do that!
Mike
Last edited by mkguitar; Dec 6, 2011 at 11:32 AM.
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Joined: Apr 2005
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From: Kentucky
I rode a 91 FLHS for 14 yrs...great bike. Had the exact problem you have twice.
The first time it was a gas cap that stopped venting. When it starts to sputter at 110 miles, crack your gas cap...if it goes away, there is your problem.
The second time it was the stock petcock filter. I switch to a Pingel...much better petcock..never a problem again.
The first time it was a gas cap that stopped venting. When it starts to sputter at 110 miles, crack your gas cap...if it goes away, there is your problem.
The second time it was the stock petcock filter. I switch to a Pingel...much better petcock..never a problem again.
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4th Gear
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Thanks for the info
Hey guys, Thanks for the replies. I have a feeling it is the petcock valve. But I am a bit concerned that the float may also be causing a bit of a problem as well. I can't be sure because I don't really know what the inside of the tank looks like and how the petcock and float on the fuel indicator relate to each other... meaning, are they anywhere near each other? It just seems strange to me that this problem always occurs at the same mileage (or close), and I'm thinking that maybe the float rides down as the gas gets used up, hits the top of the petcock and stops the flow of the gas! Does that make any sense at all? Are they close to each other so that can happen? In any case, I'll drain the tank and see what I can clean up. I appreciate all the input from everyone. Thank you, all! 
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the petcock is under the tank and the float is in the caburator two seperat items good luck let us know what it was.
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From: Phoenix '53, '88, '09 Big Twins
OP means the float for the fuel gauge.
I don't think the float can get near the petcock, anyway the entire top of the petcock has a screen ( as a "filter") over it so that the pick up tube for the main is at least 3/8" below the top of the screen.
once you take out the petcock ( and you will) you'll see how the float cannot contribute to this phenomena
Mike
I don't think the float can get near the petcock, anyway the entire top of the petcock has a screen ( as a "filter") over it so that the pick up tube for the main is at least 3/8" below the top of the screen.
once you take out the petcock ( and you will) you'll see how the float cannot contribute to this phenomena
Mike
Last edited by mkguitar; Dec 6, 2011 at 10:55 PM.