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lean symptoms when low on gas

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108
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lean symptoms when low on gas

#1

Post by 108 » Sat Aug 23, 2008 6:54 pm

Do any of you who are running Linkerts (or any carb I suppose) notice it running different or acting lean when its real low on gas ? I dont thinks it causing a problem but my set-up has 3' tall stainless mesh strainer down over the fitting up inside the tank, a Pingle type valve in the left tank, a glass filter and 5/16" hose to the bottom of the Linkert float valve fitting . Runs great otherwise.



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Re: lean symptoms when low on gas

#2

Post by john HD » Sat Aug 23, 2008 6:59 pm

brass float?

john

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Re: lean symptoms when low on gas

#3

Post by 108 » Sat Aug 23, 2008 7:51 pm

No, It has Cotton's Durable float

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Re: lean symptoms when low on gas

#4

Post by john HD » Sat Aug 23, 2008 8:35 pm

vented gas caps?

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Re: lean symptoms when low on gas

#5

Post by RussW » Sun Aug 24, 2008 12:18 am

There's the theory that you can run an in-tank petcock screen, or an in-line filter, but not both. Suppose to be too restrictive to flow well, especially when low on gas. Some swear by this, others don't believe it, but it wouldn't hurt to remove the glass filter and see what happens.

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Re: lean symptoms when low on gas

#6

Post by xnoahx » Sun Aug 24, 2008 2:08 am

My bike will surge at idle when low on gas and if I give it throttle it will bog and die, goes right away when I switch to reserve, pingle type petcock with stock linkert and cotten float(would have to take carb apart and confirm float is at proper level)

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Re: lean symptoms when low on gas

#7

Post by Panacea » Sun Aug 24, 2008 2:47 am

Seems like a good reason to hit the gas station....

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Re: lean symptoms when low on gas

#8

Post by FlatHeadSix » Sun Aug 24, 2008 4:49 am

108,

Excellent description of your fuel feed system and I think your answer is somewhere in all that extra plumbing. As Russ mentioned, sight glass filters are notorious trouble makers in gravity feed systems unless they have a little "push" to help the flow through them. They are even more troublesome if there is even the tiniest bit of moisture in the fuel. Does the glass filter have a fluted paper element inside it?, the paper really causes problems after exposure to moisture.

As mentioned above, I would either keep the tank full or ditch the glass filter.

jmho

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Re: lean symptoms when low on gas

#9

Post by George Greer » Sun Aug 24, 2008 5:29 am

This did not happen to me on my motorcycle,

But surely did on my 66 Fairlane 500, 390.

Too much filter and plumming,,, sometimes, more is not better.

Got rid of everything except 1 inline filter. End of problems.

George

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Re: lean symptoms when low on gas

#10

Post by 108 » Fri Aug 29, 2008 5:52 am

Thanks guys, Your info about the glass filters being trouble got me thinking. I've run the glass filter for years with no trouble,but it had the brown fiber element. But this spring I found a lot of rust "mud" in the float bowl and decided to add a strainer inside the tank and put in the newer type, finer mesh white plastic element. Of course its designed for a pressure system but I never thought it might resist the gravity flow that much. I think a tendancy to vapor lock was a factor also. I rerouted the hose between the cylinders, were before, it had run across and behind the generator for many years with no problems. But then, the gas used to be different too.

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Re: lean symptoms when low on gas

#11

Post by hogboy52 » Fri Aug 29, 2008 5:23 pm

The in tank filter screen can catch and hold an air bubble that will slow down the fuel flow; more so when the tank is low. Going to reserve takes the fuel from the clear area at the bottom of the screen. There is a small hole at the top of the screen to burp out the air when it gets to a certain size. Drilling the hole slightly larger will let it escape more easily.

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Re: lean symptoms when low on gas

#12

Post by duoglide58 » Sat Sep 06, 2008 5:57 am

My bike has the same problem. Interesting thought about the air getting trapped in the fine mesh of the in tank filter screen. If I recall correctly, I did not have a problem with my bike running lean when my 5 gal tanks were low on fuel prior to my wreck. When I rebuilt the bike I put on disc brakes and different fork tubes than the stock drum brake setup. I ordered a stock length when replacing the fork tubes. But with the fuel starvation problems, I have been wondering if the replacement forks for a later model bike were actually shorter, making my front end sit lower such that he tank did not drain fully. Now after about 110 miles or 3 gallons the bike will backfire an miss at 70 mph. If I slow down to 50 mph or so, it will run fine. So it appears to be some sort of fuel starvation problem at a certain tank level.

I have also been through a few petcocks because over the years some of them leaked and I could not find the proper rebuild kts. I may have gone from a petcock with a coarser wire screen mesh to one of the petcocks with fine plastic mesh. If will have to drill a hole in the top or install a course mesh screen.
Thanks,
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Re: lean symptoms when low on gas

#13

Post by Motorcyclemike » Tue Sep 16, 2008 8:16 am

I seen a forum reply here one time that a guy advised to keep the fuel filter on the bike Vertical and not in between the hot cylinders..the fuel flow would tend to be pulled thru the bikes filter better by gravity........that makes the fuel flow much better....and i think it's best to use only enough fuel line to get from the tank to the carb No more then that ! No Sharp Bends or Kinks !

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