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Hey guys, got a question. I have a set of Mikuni carbs for my 78 1000 that won't stop delivering fuel. Its so bad that the fuel dumps into the filters, just pours. I have a fiberglass tank w/ dual petcocks, and each feeds straight to the carbs. Turn the gas on, first the overflow then the intake, probably into the motor! Am I supplying to much fuel, did a little test and measured each petcocks flow on a bench into two mason jar. Dead even amount and at the same speed. I've taken apart and cleaned mutiple times. Also water tested floats and they are good. Jets, clear as a glass. I can't even try to start, for fear of burning down the house. I can't figure whats up and I don't want to take it to the shop, if I can help it. Can some one give me a clue as to whats up.

As long as you are not pumping it, it's gotta be a problem with the float needle valves not closing. The vacuum diaphragm type petcocks came about for just that reason so gas would not flow without engine running. Something has to going on with either float level, needle and seat or excessive pressure. Can you start with petcocks closed, then turn them on and see if consumption keeps up with flow in. Is it possible to get to much of a head of pressure from tank to carbs? Maybe flow restriction in your gas lines would help. A smaller diameter fuel line stuffed inside yours to create a restriction just before carbs maybe. Are they stock carbs?

Well the carbs are not stock to this bike. And from the info I've got, they are probably 900's. I will take some pictures tommorow. They are Mikuni's with the bowl drain plug that unscrews from the bottom, then you can remove the main jets. Also, they are all hooked into 1 overflow rail with 1 overflow line. These have been sitting for a while, so anything is possible. You mentioned the vacuum diaphram petcocks. Would they not function properly if the gas cap is not sealing right.

They would have nothing to do with the gas cap. If gas cap is sealing to tight then eventually gas flow will slow down.But that don't seem the issue. Still leaning towards floats. What do you mean water tested floats? Could the little adjustment tab be bent and level is set way to high. Floats will sit higher in water than gas.

Is there any chance you capped or tied the bowl vents together?

I had (still have) the same problem with my 81 KZ1000 CSR. I have the carbs out on the bench and I have on order 4 float valves (get them from Z1 enterprises) they charge way less (1/2 the price or less) than say like bike bandit or thrifty rider. I also ordered the float valve O'rings because I suspected that gas was leaking around the outside of the float valves. My bike has the vacuum petcock and even though it mostly shuts off the flow of gas, my airbox would still accumulate about 1/2 a cup of gas into the airbox overnight. I will let you know whether my fix works, maybe it will help.
Grant.

Sorry its taken me long to reply, long hours at the office this week and lack of sleep put me to bed early and out late. Anyway, I water tested the floats by removing and submerging in a bucket of water to check if they have any holes. I have an 82 Trail 110 that had that problem. It wouldn't stop the fuel because the float had developed a hole from sitting in gas for 10 years, it would fill with gas and not float. I'm leaning towards the float needles, I think the internal spring on the pins have developed memory and aren't working like they should.

Het rgpbeme, what do you mean capped or tied bowl vents together. I know they are on one connected overflow with a single outlet for all four. I'm not sure that I fully understand the question.

I also need a little help finding out which year and for what these carbs orignally go to. Here is a pic of the bottom side. My buddy told me that these are hard to find, if you pulled the drain plug, the main jets can be removed without removing the bowl.

Post edited by: OGKZCAT, at: 2006/09/30 09:15

Hope this pic shows up

Post edited by: OGKZCAT, at: 2006/09/30 10:17

I figured out that I have 29mm smoothbores. After complete disassembly I figure that the float needle seats and needles are not mating correctly. I plan on ordering rebuild kits because now the bowl gaskets are leaking, probably from all the tampering. New question, does anyone know what bike came with 29mm smoothbores. I need to know so that I can order kits, its the only way these parts site identify them. Thanks for everyones time and input. I deeply appreciate it.

No KZ came with 29mm smoothbores. These are race only carbs. They do work real real good.

Rom, I finally figured ot that they are 29's over the weekend. Now finding the parts. I talked to Jeff at Z-1 last night and he helped me to and has the parts. Just need to make sure I order what I need. I finally started the bike the other day. Would turn on the gas fill the bowls turn it off. Fired first try, quiet responsive. I like. Thanks for all the help.