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Old 05-27-2013, 08:10 AM   #16
Trials/Rider OP
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Joined: Jun 2009
Location: 35° 3' N 106° 37' W ...New Mexico
Oddometer: 50
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Originally Posted by Trials/Rider View Post
This is why I asked; I rode in to work yesterday with ~ 3g or so of fuel and when I started pulling up to the house (slight grade up hill) and noticed it starting to run like crap. I pulled up to the garage to back it it and was really running bad. I have clear fuel lines on and noticed that the right side was full of air while the left side was fine? I opened the right side fuel valve and it instantly fixed the problem.

But since both valves go into a fuel cutoff solenoid, then back into a tee how can this happen if there's fuel? I'll stick something in and try to measure the fuel tonight and report back what I find. Better yet, I'll drain the one side and see if it's just starting to reach the reserve level.
I was curious what others experienced, and like Squish said it seems to runs better with both open. If I still had the black rubber fuel line I wouldn’t have seen this to understand what was going on.
t/r

So, I drained the gas to find it was pretty low ~ 1 pint before getting air. So what I've experienced was driving up hill to my house it was simply running out of gas. I decided to drain and see how much gas remains with reserve and have about 2 liters on the left side and 1.5 on the right.

So I topped off the tank and went for a ride and seemed good, except when I stopped at a friends house yesterday (with about a half tank gas) I noticed that the right didn't have fuel in the line??? I't obviously wasn't out of gas, and was running good - so it had fuel in the bowl. I tried to rev it up, I tried switching to reserve but nothing I did fixed this.

So here's the list of events before I noticed this, maybe its normal? Was running down interstate 75mph, to a fast street 50mph, to small residential (rural area) that I could drive 35mph to his house.
While waiting for him to unlock the gate, I had it running on the side stand, idle was pretty high (from running hard?). I removed my gloves/helmet and rode into the yard when I noticed the fuel line wasn't full.

Not sure if this is normal when the bike is sitting on the side stand when running? I would have thought the gas would flow to both sides equally with plenty of fuel?

Not sure why the same side ran out of gas when it was low? Wonder if something isn't right with the carb?

Anyone have experience with this?
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Old 05-27-2013, 08:33 AM   #17
Stan_R80/7
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Location: VA
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I run with the left open and the right closed with a cross feed tube between carburetors on my '78 with dual fuel petcocks. When the left side runs out of fuel, the right petcock is opened and the fuel level equalizes between the left and right sides. When reserve is opened, either petcock will allow all fuel drained but setting both petcocks to reserve will distribute fuel better.

Generally, when the right petcock needs to be opened I get more fuel. Occasionally, the reserve is opened before getting fuel. Using this technique, I have never run out of fuel. YMMV.

p.s. the petcock tank is positioned down for normal operation and up for reserve.
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Old 05-27-2013, 08:38 AM   #18
Plaka
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Originally Posted by Stan_R80/7 View Post
I run with the left open and the right closed with a cross feed tube between carburetors on my '78 with dual fuel petcocks. When the left side runs out of fuel, the right petcock is opened and the fuel level equalizes between the left and right sides. When reserve is opened, either petcock will allow all fuel drained but setting both petcocks to reserve will distribute fuel better.

Generally, when the right petcock needs to be opened I get more fuel. Occasionally, the reserve is opened before getting fuel. Using this technique, I have never run out of fuel. YMMV.

p.s. the large lever is positioned down for normal operation and up for reserve.
I'd start off running with the right open. Then when you open the left you don't have to move your right hand from the throttle/brake.
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Old 05-27-2013, 10:04 AM   #19
Stan_R80/7
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I often pretend I am British, e.g. substituting left for right and wanting to using the phrase "do that again and I will smack your bum you saucy tart". YMMV.
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Old 05-28-2013, 06:55 AM   #20
dm635
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Originally Posted by bizalich View Post
from one nOOb to another... i have 2 fuel taps, and run both open.

When i need reserve, i switch both to reserve at the same time and start looking for gas. Normally my butt hurts or i need a coffee before i run out of gas, but i have had that panicky moment when fuel is gone and you need to switch to reserve in the middle of a corner or on the highway... in which case i normally have about 20 minutes before i am walking.

also, i am in the habit of turning OFF both petcocks like 3 blocks before i get to my house after a ride. This way neither side leaks when it is in the garage.

Actually, now that i think about it, not sure if this is a good practice or not? Can it cause some sort of carb problem i dont know about?

Sounds like we do the same thing. I turn both on & also close them before I get home.

I found out shortly after buying my bike that the reserve tubes were clogged. They were plugged solid & had to call someone to bring me gas. They were cleaned out last year & I'm waiting for petcock rebuild kits. Occasionally the left valve will drip after closing. Every once in a while I'll flip to reserve after a fill up just to keep all flowing.
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Old 05-28-2013, 09:53 AM   #21
bizalich
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new fuel taps

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Originally Posted by dm635 View Post
Sounds like we do the same thing. I turn both on & also close them before I get home.

I found out shortly after buying my bike that the reserve tubes were clogged. They were plugged solid & had to call someone to bring me gas. They were cleaned out last year & I'm waiting for petcock rebuild kits. Occasionally the left valve will drip after closing. Every once in a while I'll flip to reserve after a fill up just to keep all flowing.
hey dm635-- I actually just bought 2 new fuel taps, fuel line, and the screen tubes... all told with shipping to italy it was like 100euros. After 35+ years, i figure that is pretty good lifespan. I started by removing the fuel taps, seeing they looked like clogged up shit, and then pulling them apart to rebuild them... it is pretty easy, but when i really started to look at mine, the time it would take, and the fact that all new units are really not that expensive... i just went for the new. This way I have the comfort in knowing that this part of the bike is completely dialed for (hopefully) another 35 years.

This actually makes me think of a separate topic that could turn into its own thread... or at least a roundtable discussion with a bunch of airhead monkees-- and that is: when do you make the decision to rebuild something or just throw it out and buy new? Obviously, if money is a factor, granted. But other than that--is it worth the piece of mind knowing that the bike is getting slowly MORE reliable than stock, or is it better to "stick with what works", knowing that ze'germans were always right. (if you dont believe me, just ask them!)

some initial topics here could be: rebuilding fuel taps, points or electronic ignition, original wiring harness or updated/simpler, airbox and aircleaner modifications...

alright, anyway--this is where i bought the fuel taps: http://shop.siebenrock.com/index1.ph...001&sprache=en
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Old 05-28-2013, 12:18 PM   #22
dm635
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The rebuild kits come with all parts. I had an o-ring come apart on the left side when disassembled. I feel that is most likely the part causing the intermittent drip. Kit comes with orings, disc's & the screen with another seal. Also ordered an owners manual.
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