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 Post subject: Fuel Supply Problems 28MM
PostPosted: Sun Oct 16, 2005 2:11 pm 
I have tried at least a dozen ways to run my fuel lines to the 28 mm carbs but I think they keep starving for fuel. I keep getting air bubbles in the fuel lines and losing power. I have done everthing including custom fabricated splitters, four seperate lines, hard lines, quick disconects, with shutoffs, without shutoffs, Tee's, Y's, elbows........<br>Do I need to add a fuel pump?? Why do I get air in the lines constantly??
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mchadwick@charter.net


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 Post subject: Re: Fuel Supply Problems 28MM
PostPosted: Sun Oct 16, 2005 11:20 pm 
I had almost the same experience with my 28mm flatslides. I have removed the internal fuel filter in the tank and run 2 separate lines, 1 for each carb bank. I have an external fuel filter and inline fuel switches in each line. Once fuellevel got below approx. 5 ltrs, I got discontinued fuel supply.<br>I installed an electric fuel pump then which worked fine but I had the impression that mixture got slightly richer - maybe the fuel pressure against the needle valve raised fuel level in the bowls a little?<p>I have then removed the fuelpump again, re-routed and cleaned-up the the fuelline setup so that fuel was constantly flowing downwards and the problem seems to be solved for now.<p>You usually have the fuel lines much longer than they would have to be in normal operation, since you need the extra length when lifting the tank. That extra inches of fuellines can arrange themselves in a way that they partially are above fuel level in the tank thus discontinuing the flow. I hope my description is somehow clear and logical, but it seems to having cured my problem.
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wolfgang_hromada@aon.at


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 Post subject: Re: Fuel Supply Problems 28MM
PostPosted: Mon Oct 17, 2005 4:13 am 
Thanks Wolfgang,<br>What diameter fuel lines are you running? Were there any other drawbacks to using the fuel pump besides the mixture change.<br>I don't have mine dialed in yet so I could adjust accordingly.<br>Do you know if anyone has used positive tank pressure to act like a fuel pump? I could tap a line off the middle of an expansion chamber and run the line with a filter to a modified gas cap to pressurize the tank. This is done in RC Airplanes. It works great for them.<br>Mark
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mchadwick@charter.net


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 Post subject: Re: Fuel Supply Problems 28MM
PostPosted: Mon Oct 17, 2005 4:32 am 
I am running 8mm ID from the tank through the filters and fueltaps, then I have a T-connector which runs 6mm ID lines to each carb then. I have 2 independant such setups, 1 per carbbank.<br>There was no issue with the fuelpump other than extra weight. The pump was off an ZX-6R I think and it has a kind of fuel pressure switch. It makes "tick-tick-tick" until the bowls are full, and then only ticks every few seconds to replenish the fuel into the bowls. Current consumption is 1A peak, but no issue, I am running a very small 1.8Ah Gel battery and had no problem.<br>A positive side effect of the fuel pump is that it cuts off fuel supply when off so no need for extra fueltap.
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wolfgang_hromada@aon.at


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 Post subject: Re: Fuel Supply Problems 28MM
PostPosted: Mon Oct 17, 2005 9:08 am 
I've had 28mm flat slides on my bike for 5 years without a fuel pump, air bubbles or delivery issues. Like Wolfgang said, fuel runs downhill. Make sure every single fuel line you have runs downhill. To help this along, and to clean up the left side of my bike and to make routing lines easier, I moved my petcock to a bracket on the left, upper radiator mount.<p><img src="http://i18.photobucket.com/albums/b142/WynB/UpperLeftMount.jpg" alt="Image hosted by Photobucket.com"><p>Along with the move, I turned the outflow nipple of the petcock so it was pointing to the right side of the bike. <p>Then I made the fuel lines like this:<p><img src="http://i18.photobucket.com/albums/b142/WynB/IM000985.jpg" alt="Image hosted by Photobucket.com"><p>To orientate you, the short black line at the bottom on the "spider" is the line that connects to the petcock. That then goes to a stock fuel "T", then to another stock fuel "T", then to the carbs. The lines going to the right in the picture, go to the left side carbs. The lines going to the left in the picture, go to the right side carbs. All the black line is 3/8", the blue line is 1/4". I safty wires all the lines instead of trying to find clamps, a lot easier and much cleaner looking. I do have a clamp where the fuel line goes into the petcock.<p>That's it, years of great service and pretty simple.
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RZVWyn@aol.com


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 Post subject: Re: Fuel Supply Problems 28MM
PostPosted: Mon Oct 17, 2005 10:10 am 
Wyn,<br>did you or somebody else ever run the bike with throttle fully open for a short while? I


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 Post subject: Re: Fuel Supply Problems 28MM
PostPosted: Mon Oct 17, 2005 1:35 pm 
Mid 80's Goldwings pumped air into the fuel tank. If you don't want to drill a hole in your exhaust you could steel a pump off one of those.
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beeks81@aol.com


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 Post subject: Re: Fuel Supply Problems 28MM
PostPosted: Mon Oct 17, 2005 1:45 pm 
Have you checked you fuel tank cap vent.
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daverize@sbcglobal.net


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 Post subject: Re: Fuel Supply Problems 28MM
PostPosted: Mon Oct 17, 2005 3:19 pm 
Yes, it flows plenty of gas.
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RZVWyn@aol.com


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 Post subject: Re: Fuel Supply Problems 28MM
PostPosted: Wed Oct 19, 2005 6:23 pm 
I looked at that a little, cruised around with a piece of foam instead of a gas cap. It did seem better.<br> Is there an easy test for the cap vent?
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mchadwick@charter.net


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 Post subject: Re: Fuel Supply Problems 28MM
PostPosted: Wed Oct 19, 2005 7:39 pm 
Looks like a clean set-up. Good short lines. <br>Thanks for the help.
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mchadwick@charter.net


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 Post subject: Re: Fuel Supply Problems 28MM
PostPosted: Wed Oct 19, 2005 7:43 pm 
The ones from the petcock to the carbs are short, the ones from the tank to the petcock are a little longer, but much straighter.
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RZVWyn@aol.com


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 Post subject: Re: Fuel Supply Problems 28MM
PostPosted: Wed Nov 02, 2005 8:12 pm 
I tried more configurations without a pump and had no luck. I put a ZX6 fuel pump on the bike tonight and it is screaming....<br>It is the first time I have had full consitent power. Now I know what this bike is supposed to run like. Whew!<br>It didn't miss a beat.<br>Thanks for the help!!!<br>
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mchadwick@charter.net


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 Post subject: Re: Fuel Supply Problems 28MM
PostPosted: Fri Nov 04, 2005 8:50 am 
Are you able to tell if it runs richer with the pump?
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wolfgang_hromada@aon.at


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 Post subject: Re: Fuel Supply Problems 28MM
PostPosted: Fri Nov 04, 2005 6:05 pm 
The bike was so screwed-up without the pump I have no idea what the correct jetting should have been. The bike ran like a moped, really. I have not tweeked the jetting yet but I will let you know where it ends up.<p>I have an idea that becuase the carbs for the rear cylinder are higher on the bike they tend starve as the fuel in the tank gets lower. I'll bet this adds to the increase in failure or scoring of the rear cylinders. <br>The pump is the only thing that would make this thing run. Thanks again!!!!<br>P.S. I know it's a little heavy so I took an 1&1/2 pounds of padding out of my helmet to keep the combined bike and rider weight the same..smart thinking, eh? The only other option was to drink one less beer but I couldn't give that up.
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mchadwick@charter.net


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