fuel in airbox and engine head - ATVConnection.com ATV Enthusiast Community



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Old 01-06-2017, 10:30 AM
Weekend Warrior
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Default fuel in airbox and engine head

I have a 2000 Kodiak 400 Atv. A month ago it started backfiring and then wouldn't start. Figuring with the age and years of ethanol I bought a new carb and a new petcock. The fuel runs straight through the carb and fills the cylinder head and the airbox AFTER I shut it off. This also is what it did before I bought the new parts. I am at an absolute loss as what to do next as it makes no sense at all. I figured when the fuel got to the float bowl and it filled that would stop flow fuel. I even got a third new carb and it did the same thing. Anyone have any ideas? I know it has to be a vacuum leak but not sure where else to look after plugging off port to back brake. Thanks in advance
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Old 01-06-2017, 11:44 AM
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So...ya need to validate your float & seat are functioning...only way to do that is kinda messy...


1) Remove carb, but leave fuel line attached
2) Remove the float bowl
3) Turn your petcock on (carb should be held relative to mounting position)
4) Fuel should flow freely out of the bowl (this is the messy part)
5) Manually (fingers) push the float up
6) With float pushed up fuel flow should stop


If anything else is going on there is something wrong...
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Old 01-06-2017, 11:55 AM
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I actually checked the original carb and it was working properly and was mad at myself for buying a new one and then the company sent me another one all with the same results. Is there anything on the cylinder head side as I installed the new carb that could cause a vacuum leak? After all ,the line to the fuel tank(which I replaced with the new petcock. and the vacuum to the rear brake are it, outside of the seal to the cylinder side and airbox out. The start of all this started with the hose that comes off the bottom of the float bowl started leaking all the fuel out of the tank when not running.

Last edited by stevekis; 01-06-2017 at 01:09 PM. Reason: more info
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Old 01-06-2017, 02:26 PM
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Not sure what you mean by vacuum leak...that would just be an excess air (lean condition) issue...


The tube coming out the bottom on the float bowl is a drain, I believe, as the parts diagram shows a drain screw right next to it...


The only way fuel floods the engine & air filter is by the float seat not sealing properly.


My son's LT80 does this often...I just got used to shutting off the fuel at the petcock whenever it's not running...
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Old 01-06-2017, 02:51 PM
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I am grasping at straws because I have no idea what to try. It will run perfect for a while then start to sputter(like it is being flooded) and I shut it off and look and the airbox is full of fuel and the cylinder head is full as well. I did what you said and the float works properly on all 3 carbs but as soon as I shut off the engine the gas continues to flow through the carb. and into airbox and engine.
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Old 01-07-2017, 10:25 AM
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Are the new petcock & fuel line stock parts? Do you have a manual? You may want to see if it talks about float level adjustments. While it may seal completely when you do it manually, the floats may not be applying enough up pressure to seat the float needle completely...sometimes the float needle tabs can be bent to have the needle seat quicker as the bowl fills...
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Old 01-08-2017, 07:29 AM
Weekend Warrior
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Default floats

Fuel Star petcock and fuel line. I sometimes forget just because something is new then it has no issues(na´ve on my part) I will take off the bowl again and bend the tabs a little(I have no manual because I never needed one until now). Thanks for your feedback and you are right about the possibilities for this problem.
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Old 01-08-2017, 10:40 AM
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After all we discussed and I sat down and went through every facet of the original carb and what prompted me to buy new parts, I figured out what had happened. While I had cleaned and checked needle valves and changed O-rings and stuff, I never checked the float seat to see if it was sealing(it was not). That being said, I got it to seal and hopefully tomorrow when the temp rises I will reassemble and post the outcome. Thanks for making me "think".
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Old 01-09-2017, 11:55 AM
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anytime...
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Old 01-10-2017, 11:02 AM
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Default Celebrated too quick

Original carb back on and only difference between it and the new one
I bought is the fuel is draining through the drain hose and not running into the air box. That means the fuel is not shutting off on any one of the three carburetors. When I did your test all three of them closed properly with a bowl removed. It has to be something simple or all three carbs would not do the same thing. I can't think of anything else to try so I guess I will break down and take it to the shop.
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