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How to get fuel to the carbs without a tank 21 Jul 2021 19:35 #852245

  • motoaddict
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Hi Gang!

Ok so I got the ol' KZ ready to start, checked all the boxes, good spark and compression. Rebuilt the carbs and checked the electrical systems and all seems ok. So tonight I went to try and start it for the first time by feeding it gas through a home made bladder of sorts. Ok its a gatorade bottle with polyethylene tubing with a shut off valve. the bottle is open at the top so it would not vapor lock. We hooked it all up put gas in and opened the shut off valve and watched a bunch of bubbles come up through the gas in the bottle and the level go down. The bubbles were the first clue we did something wrong. Tried to start it and nothing. Out of curiosity I loosened up a carb bowl drain screw and nothing! Seems the gas did not reach the bowls at all. The gas tank for now is out of the question so what is a reliable way to feed fuel to these carbs to try and get it to run. My little rig did not seem to work. Not really sure why either. Aren't the two vent hoses supposed to allow air to escape and prevent vapor lock? What am I missing?  Thanks! 

 

 

 
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How to get fuel to the carbs without a tank 21 Jul 2021 20:03 #852250

  • Nessism
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Your feed bottle is way too high, otherwise it looks fine in concept.

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How to get fuel to the carbs without a tank 21 Jul 2021 20:06 #852251

  • DOHC
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It seems like that should work.  Where do those vent line hoses go?  You could just pull the vent hoses off and see what happens.  You don't need them for test running.  Did you confirm that fuel was flowing out of the supply tubes when they were not connected to the carbs?

I've been using this tank for a while now.  amazon.com/gp/product/B004NV42PQ/

You also shouldn't need to hang it so high above the bike.  I haven't had any trouble running bikes with my tank handing from the handlebar.  I've done this with three different bikes so far.
'78 Z1-R in blue, '78 Z1-R in black, '78 Z1-R in pieces
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How to get fuel to the carbs without a tank 21 Jul 2021 20:48 #852253

  • 750 R1
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  I use old lawn mower fuel tanks, they are perfect for the job and have a fuel tap and vent....

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How to get fuel to the carbs without a tank 22 Jul 2021 03:51 #852266

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Thanks for the Advice, I will shorten the hoses and have it hang just above the carbs. Yes we also confirmed fuel flow before connecting everything. The tubing is only 1/8" ID, maybe too small?  The vent hoses, which are longer than necessary,  just hang off to the side of the bike. I can also try pulling them off since they are not really needed for now. If this doesn't work I can dig around for an old lawn mower tank. Thats a good idea. 

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How to get fuel to the carbs without a tank 22 Jul 2021 05:47 #852270

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Would the excessive fuel pressure from hanging the bottle too high overcome the resistance on the float shutoffs and cause the bowls to overflow?  Curious because I just used a similar setup to run my Z1 for the first time and hung the bottle about as high as Motoadict did; and immediately all 4 bowls started overflowing.  I quickly took the bottle down and put it lower than the carbs to stop the overflow but I couldn't figure out why the floats were sticking since they just came out of the ultrasound tank and are squeaky clean. 
KZ900, Z1A

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How to get fuel to the carbs without a tank 22 Jul 2021 06:08 #852271

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Would the excessive fuel pressure from hanging the bottle too high overcome the resistance on the float shutoffs and cause the bowls to overflow?  Curious because I just used a similar setup to run my Z1 for the first time and hung the bottle about as high as Motoadict did; and immediately all 4 bowls started overflowing.  I quickly took the bottle down and put it lower than the carbs to stop the overflow but I couldn't figure out why the floats were sticking since they just came out of the ultrasound tank and are squeaky clean. 

Yes, that is usually the risk of putting the fuel supply too high. I also use a plastic lawnmower tank suspended from the handlebars. I think Martin uses an IV stand, which is adjustable.
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How to get fuel to the carbs without a tank 22 Jul 2021 06:12 #852272

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Perhaps the small diameter plus the rag covering the vent slowed the flow to a trickle.
1982 KZ1000 LTD parts donor
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2000 ZRX1100 not ridden enough

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How to get fuel to the carbs without a tank 22 Jul 2021 09:54 #852279

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I have an old tank from a Briggs vertical 8 hp. Works great. Already had a gas cock. Added a filter and splitter. Hung from a 3’ step ladder just abut the right height the mimic tank height

 
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
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1978 KZ 1000 B2 LTD
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How to get fuel to the carbs without a tank 22 Jul 2021 18:20 #852308

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The fuel at that height is not a problem.

Usually after installing carbs the floats get stuck.  A quick tap on the bowls with the butt end of a screwdriver will usually sort it.
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How to get fuel to the carbs without a tank 22 Jul 2021 19:26 #852310

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Ok so I redesigned the gas bottle to be much lower with larger diameter tubing. Pulled the vent hoses off and got the fuel lines all hooked up and poured about two fingers of gas in and....nothing. Not a drop went down below into the short clear tube. Total air lock. It must be the float vales stuck but they were brand new valves in new valve seats. I just don't under stand how they get stuck in the up position. And all 4 at the same time? What if I shoot a little compressed air down the fuel line. Would that be enough pressure to pop the float valves open? I will pull the carbs this weekend and investigate.

 
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How to get fuel to the carbs without a tank 22 Jul 2021 19:35 #852312

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Try venting the bottle 
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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