Gasleaking from air box?

If it's broken or just needs tweaked

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LiveToRide95
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Gasleaking from air box?

Postby LiveToRide95 » Sat Mar 15, 2014 8:53 pm

Heres the situation I have a 1981 cb650c. Last year it stopped running so in the winter I pulled the carbs, cleaned and inspected them thoroughly, Removed all rust from gas tank, sealed gas tank with caswell tank seal kit, and replaced the battery. I finally got around to putting it all back together today after giving her fresh paint. I hook everything up, turn the petcock on and slowly gas begins to drip from the vent hole in the air box. I tried to start it and she didn't want to turn over at all. She cranked and cranked but no luck. I made sure each float bowl had gas flow when the petcock was turned on. I pulled the spark plugs and they where slightly damp and smelled of gas. I am by no means a motorcyle mechanic but I do my best. However I have no idea what to do, any help is apprecaited!

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Folsoml
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Re: Gasleaking from air box?

Postby Folsoml » Sat Mar 15, 2014 9:28 pm

It sounds like a float needle or two got stuck open and the gas overflowed into the airbox. Did you try tapping on the float bowls with a screwdriver handle after you reinstalled the carbs?
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LiveToRide95
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Re: Gasleaking from air box?

Postby LiveToRide95 » Sun Mar 16, 2014 9:25 pm

I did try tapping the carbs with a wrench handle but no luck. I have solved the starting issue, I think the engine was just flooded. I left the gas off an spray some jump starter fluid in the air filter and it started right up. Ran very rough but it started. I guess I'm gonna have to pull the carbs and go through them again tomorrow:(

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Folsoml
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Re: Gasleaking from air box?

Postby Folsoml » Sun Mar 16, 2014 9:46 pm

LOL! I've never done anything to a set of carbs that did not require me to take them back off about three times before it's all said and done.
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LiveToRide95
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Re: Gasleaking from air box?

Postby LiveToRide95 » Sun Mar 16, 2014 11:34 pm

Well that does it, now you've gone and jinxed me... Lol anything I should look for other than stuck floats?

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Folsoml
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Re: Gasleaking from air box?

Postby Folsoml » Sun Mar 16, 2014 11:59 pm

That's all I can figure. The fuel should fill the bowl until the float rises and the needle plugs the fuel inlet. When the needle sticks, the fuel keeps flowing until it overflows (forgive me if you are already aware of this). Unfortunately, you can really even look for stuck floats. Once you take the bowl off, they're going to work perfectly. If you've made sure the floats are bouyant like the should be, all you can do is make the surface as smooth as possible for the needle. If you've not already done it, polish the float seats with some kind of metal polish until they shine like a new penny--inside and out.
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LiveToRide95
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Re: Gasleaking from air box?

Postby LiveToRide95 » Mon Mar 17, 2014 9:10 am

I was aware of how the floats work but a quick refresher course is always nice! However I didn't know about not being able to tell if a float was stuck once you take the float bowl off. We just got about 6" of snow here so I will probably pull the carbs tomorrow. Thanks for the help!

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Folsoml
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Re: Gasleaking from air box?

Postby Folsoml » Mon Mar 17, 2014 11:59 am

The thing that is usually going to make them stick is just a burr or piece of crud that is keeping the needle from sliding smoothly. Since tapping it with a screw driver will often free it, the process of removing the carbs and taking the bowls off will almost certainly do it.
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LiveToRide95
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Re: Gasleaking from air box?

Postby LiveToRide95 » Mon Mar 17, 2014 4:02 pm

Okay thanks alot for the help!

LiveToRide95
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Re: Gasleaking from air box?

Postby LiveToRide95 » Tue Mar 18, 2014 8:23 pm

New update I pulled the carburs today and cleanded them real well again. Taking specific care on the brass needel seats(or whatever you call them). Then reinstalled them, the bike runs fairly well and no gas comes from the air intake while running.
However whenever you shut the bike off but leave the gas on even for a second or two gas starts leaking again... I dont know if this makes a difference but the vaccum shut broke about a year ago. So I took it off and just bypassed it. Its been that way for awhile and I haven't had this problem. Any other ideas?

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Re: Gasleaking from air box?

Postby MiGhost » Wed Mar 19, 2014 2:15 am

If you have cleaned, and tested the float valves. Some other things that could cause the problem are a bad float, or sticky float pin.
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LiveToRide95
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Re: Gasleaking from air box?

Postby LiveToRide95 » Wed Mar 19, 2014 2:49 pm

I pulled my carburetors today again. I checked the floats to make sure they were not damaged and check the float pins to make sure they were not sticky. I went ahead and put gas in it before putting it back on the bike so I can watch where gas was leaking from. There's gas coming up from underneath the jet needle which would be where it's leaking from if the needles are not stopping the gas. Correct? I have cleaned the brass needle seats very thoroughly and check that all the needles are in good condition. I I am no motorcycle mechanic and I have no idea what to do next. Any ideas?

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Volker_P
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Re: Gasleaking from air box?

Postby Volker_P » Thu Mar 20, 2014 2:13 am

Some here reported carb fuel leakage with the vacuum tees between carbs 1+2 and 3+4 being cracked. But I think it should not leake there any more after shutdown of the engine. This rather sounds like floater valves.
The floater cams are very sensitive to bending or surface damage. Mixing up parts between different carbs may cause trouble here.
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LiveToRide95
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Re: Gasleaking from air box?

Postby LiveToRide95 » Thu Mar 20, 2014 10:02 am

I definitely have not mixed up parts between the carbs. I tear one down at a time then reassemble it then move on to the next one. Excuse my ignorance but what do you mean by floater valves and floater cams? I'm not too good with all these official names. Lol

LiveToRide95
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Re: Gasleaking from air box?

Postby LiveToRide95 » Thu Mar 20, 2014 10:30 am

is it possible that the rubber tips on the float needles have hardened and I'm not feeling properly anymore? I did a visual inspection but I am no motorcycle mechanic... They looked good to me though.


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