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Discussion Starter · #1 ·
What could be causing the gasoline to be coming out of the needle jet as a liquid? My bike hasn't been running right lately and I found the inside of my airbox soaked with gasoline and noticed that using throttle caused gas to actually splatter out of the carb. I thought it was all supposed to be a vapor once it went through the jet, so what is the cause of this??? The needles don't look worn, and nothing is jumping out at me...

I'm getting really frustrated with this bike!!!
 

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Sounds like your main jet is too big. Have you done any carb work or
rejetting recently?

The gasoline doesn't vaporize... it atomizes.

When the air goes through the carb and passes through the venturi,
it creates a low pressure area.
The higher pressure area, in the float bowl, pushes the fuel up through
the jet (same effect as blowing across the top of a straw in a glass of water).
Once the gas has cleared the top of the jet or needle seat, the flowing
air atomizes the fuel.

If you don't have enough air flow (bad compression, etc) OR
a too big of a main jet can prevent the fuel from atomizing in the venturi.
 

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Discussion Starter · #3 ·
The jets are the stock size. Other than a UNI filter the bike is stock, plugs have looked fine. The bike has always started great and run down the road fine, nothing that would point to low compression, but it is something I will check in to.

One website I can across suggested that the needle seat could be worn and causing me my problems. What's your take on that?

http://www.factorypro.com/tech/needle_jet_wear.html

I forgot to mention that other parts of the carb were soaked in gas too, including the air joint pipe.
 

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downinit25i said:
The jets are the stock size. Other than a UNI filter the bike is stock, plugs have looked fine. The bike has always started great and run down the road fine, nothing that would point to low compression, but it is something I will check in to.

One website I can across suggested that the needle seat could be worn and causing me my problems. What's your take on that?

http://www.factorypro.com/tech/needle_jet_wear.html

I forgot to mention that other parts of the carb were soaked in gas too, including the air joint pipe.
It's very possible that the needle seat is worn, if we're talking about
the '85 in your sig pic.

How many miles are on it?

If you do a lot of on the throttle/off the throttle, that would definitely contribute to wear.
Personally, that would be one of the latter things I would look at,
but I wouldn't rule out the possibility.

Check the compression and also check your float.
If the float isn't closing the fuel inlet needle, you could very easily get
fuel making its way up in to the venturi without atomizing.
Check the float level and make sure it's within spec.
Make sure the needle and seat are clean and not blocked.
Make sure the axle that the float is on allows the float to move freely.
 

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If gasoline is spattering OUT of the carb, into the airbox, it would suggest to me that the valves aren't closing all the way. (The piston is moving into the compression stroke, and pushing air back out through the carb.) This was always a symptom of a leaky reed valve in a two-stroke, so I wouldn't overlook the possibility of it in a 4 stroke, even though the valves are completely different.

Do you have a way to do a leak-down test, or at least get the compression checked?

--Justin
 

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Discussion Starter · #7 ·
I don't think that I have a way to check it, but I can put it all back together and take it to the dealer if I need to. Hopefully they'll just let me borrow a gauge. I took a good look into the engine and I could see one of my intake valves and it was covered in carbon pretty good.

The float heights were fine and the float valves looked fine too. I took the needles out of their holders and placed them in the seats and there was some play to them side to side. Is that designed into them or would that indicate that they're wearing down?
 

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Discussion Starter · #8 ·
Ok, here's the update. I gave my carbs a complete cleaning and it seems to be running a bit better. The needles had a bit of wear to them:



And it looks like the needle jets have some wear to them too:



Now I was really concerned about whether my timing is off and I'm getting leak back on the compression stroke. I couldn't find anybody with time to get me to the dealer to talk about all this and get a compression test done, so what I did was take a piece of paper and partially cover the inlet to the engine block. The paper sucked in real good and didn't fly back the other way at all, so I'm not as worried anymore.

The valves did seem dirty to me, maybe one of you can tell me how bad they actually are. This is what they look like:



They look way too dirty to me. So when I put the bike back together I made sure to mix up some Seafoam and I'm going to put some higher grade gas in it for a few hundred miles to see if I can notice a change.

When I was working on my carbs I tried everything I could think of to get the needle seats out so that I could stand them on a scanner and get a real sharp, close picture of it. They wouldn't come out though. Everything else was off the carbs. Is there a trick to getting them out, or are they set in there and am I looking at trying to track down a new set of carbs?
 

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downinit25i

For my '87 the manual says that the needle seat is NOT removable. Make sure you don't muck them up trying to remove them. They're probably pressed in with an interference fit.

Gumpy
 

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I had a similar problem with my Yamaha XS850. The problem turned out to be the o-ring seal around the float valve seat where it is held into the carb body. The float was set correctly but gas was leaking around the seat and over filling the bowl. I had the same symptom with fuel leaking into the air box. Don't know if your valve seats are made the same way but it's something you might check.

sanoke
 
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