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Discussion Starter #1 (Edited)
I got a good one. Yesterday my VN750 would not start. We jumped it off. I got a AGM battery coming. We finally got it started and fuel and oil came bubbling out of the front head breather. Then I noticed that fuel had been draining from my K&N pod filter. I pulled the carbs off and opened them up. The float and float valve where free moving. The float valve and seat where also fine. So, I changed the oil, filter, and plugs. Got it started and it started to do it again. My fuel petcock free flows on primary, no flow in the on position. I switched the petcock to on and I stopped.

So here are my questions:
1. What’s making my fuel leak through the carbs?
2. Is that the normal operation for the petcock?
:drool: :confused: :(
 

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I would assume (I know) that with the petcock free flowing on primary that there is some small peice of crud on the needle valve seat that is allowing fuel to flow even with the bike not running. You may not have seen it when the carb was disassembled. It only takes a miniscule piece of crud to allow fuel to seep by. Or it could be that the valve has a groove worn in the rubber seal that prevents complete closure and therefore a fuel overflow condition.
I'm not sure about your version of the petcock as later models only have off, on, and reserve with fuel flow controlled by vacuum. I would also assume that with your petcock set to on that the vacuum control takes over so fuel won't flow unless the engine is running. I don't know if yours is supposed to free flow in primary or not so someone else with an 86 would have to chime in.
 

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and the Adventure Cycle
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Using "Prime" (it's not "Primary") is the problem. The fuel will flow freely in that position. It isn't vacuum operated like "On" is.
It should only be used when first starting the bike after it's sat for awhile, then switch to on. So Yes, it is normal.
I don't remember which year they changed the petcock to Res-On-Off, but ya may want to consider getting one of those ones.
 

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Discussion Starter #4
Well that explains how the carbs got the fuel. Now, why did the fuel run into the head? Shouldn't the float valve or the needle valve stopped it in the carb? I am not a mechanic more of a shade tree. I plan on replacing the float and float valve. I don't see a way to replace the float valve seat. I have a old VN750 carb and I drilled the pin on the side of the holding arm and still could not get it out. I had to break the seat holding arms to get it out. I was not planing on replacing the needle they look new. Any input would be greatly received
 

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and the Adventure Cycle
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If there was something ever so small stopping the float valve from fully seating, given some time the fuel would fill the carbs, then flow into the head/cylinder, and if given more time, into the crank case. So it's a good thing that you changed the oil & filter.
Just remember, the petcock should never be left on Prime, and you should be OK.
And, I don't believe that Prime will act the same as reserve, so once your bike starts to sputter out of fuel, you might be totally dry, but ya may want to see if anyone else knows more about that.
 

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Discussion Starter #6
The on position on my peacock does not let enough fuel to flow to get above 30 mph. I have to switch it to prime to run at speed. I looked on bike bandit and the petcock has been discont. I don't really know where to go to find a replacement.:drool:
 

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and the Adventure Cycle
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The on position on my peacock does not let enough fuel to flow to get above 30 mph. I have to switch it to prime to run at speed. I looked on bike bandit and the petcock has been discont. I don't really know where to go to find a replacement.:drool:
Well, if you have to do that, then you'll also have to put it back to on when ya park the bike. Otherwise the fuel will keep flowing, even when not running.

Did you check
part# 51023-1392 - TAP-ASSY,FUEL $57.41 (2006 model)
or
part# 51023-1113 - TAP-ASSY,FUEL (1986 model)
(I don't think Bike Bandit gives the last 4 numbers though)

There are also other model years with different part#'s for the petcock, but #51023-1392 supersedes them all (according to Ron Ayers site anyway).
You should be able to use that one, which is one with reserve, not prime.

Or, like Fergy said, see about rebuilding the one you have.
I'm not sure what's needed for that though.

Did you check the vacuum lines (I didn't really think of that wwmkwood :smiley_th )
 

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Discussion Starter #10
It was the vacume line. replaced it and now it works fine. Thank ya'll (my southern is showing) for all the input.
 

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Your bike must have been running radically with a bad vacuum line. Usually your rpms will raise some as vacuum leaks cause lean conditions. Idle usually creeps up and is hard to control. Anyway, glad you found the problem!
 

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Discussion Starter #12
I ran fine because it was always in the prime position. I didn't have a problem until it started to warm up. My theory is that the heat caused the fuel to vaporize. Which increased the pressure in the tank. Pushing the fuel down into the carbs with enough pressure behind it to deseat the float valve and needle. Again this is just a theory and is I said earlier I consider myself a shade tree mech.:motorcycl
 

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and the Adventure Cycle
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So you can get past 30 with it in the run position now?
 

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Discussion Starter #14
Yes, it's running fine. I still need to rejet. I ordered jets from motorcyclecarbs.com.
 
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