Gas leak from carbs - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
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post #1 of 43 (permalink) Old 08-08-2019, 01:12 PM Thread Starter
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Gas leak from carbs

So the other day took 2001 v Star 650 out for first ride of the year. Smelled gas, got a few miles, determined it was coming from the bike, tried to get back home, bike died, towed home , now trying to fix. Removed tank and breather box from top of carbs , took bowl off front carb expecting to have stuck needle valve. Float and needle valve came out with no problems so that needle did not seem to be stuck. Put carb back together, put breather box back on, and now when I tighten the clamp that holds the breather box to the top of the carb throat it pushes the rubber boot up and off of the carb. When I first removed the breather box it came off with no problem, I did not even have to loosen those clamps which didn't seem right. I'm pretty sure that's where the gas was leaking out of ...where the breather box connects to the top of the carb throat as far as I could tell at the time. Any thoughts?
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post #2 of 43 (permalink) Old 08-08-2019, 01:22 PM
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My first thought is gas shouldn't be leaking into the breather box. I wonder if the jets are clogged.

I ain't lost until the tank is empty!
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post #3 of 43 (permalink) Old 08-08-2019, 02:12 PM
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if the float is stuck low in either carb float bowl there is an overflow tube that goes down just above the top of the crankcase on the right side of the bike.

If the tube is in place and not crushed it lets the fuel leak out where it wont hit the exhaust and combust into flames

If that tube is pinched off I guess its possible the carb could fill to the top with gas, but I think it would also fill the cylinder with fuel, ruining your oil by dilution.

you said you took the front float bowl off, it could have been the rear float that was stuck

those clamps on the bottom of the air box can be a PITA sometimes to get back on - you tighten the screw.. almost snug... and it pops off.

I think over time and heat the airbox deforms and no longer wants to sit in place

try cleaning the top of the carb, the inside of the airbox, the clamp.. with alcohol and wipe it all down dry so its plastic to metal contact, with no oily gas acting like lube. The engine breather hose goes into the airbox, venting the oil fumes from the crankcase, so the inside of the airbox normally gets oily.

Reading your post again, did you see gas leaking out of the bike anywhere?

with a carb'ed engine its normal for it to smell like gas when the engine is hot. The gas in the float bowls literally boils out when the bike is parked hot, and you smell the fuel vapor coming off the engine.

That does not happen with fuel injected vehicles, so most people are not use to gas engine smelling like gas anymore.

one more thing - if this is the first time you rode this year, your gas has probably turned goopy unless you used a fuel stabilizer in the tank when you parked the bike for the winter.

if you did not stabilize the fuel when you parked it last fall, I would drain the tank, fill it with fresh gas, and use something like Seafoam to clean out any gunk in your carbs. As long as the bike will run Seafoam will do the job.

If you cant get the bike to start again it may have sucked some goop in from the tank. In that case you will need to get some seafoam into the float bowls, and let it soak overnight.
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Last edited by KCW; 08-08-2019 at 02:19 PM.
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post #4 of 43 (permalink) Old 08-08-2019, 02:27 PM Thread Starter
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Yes I saw gas dripping from the carbs and as best as I could tell it looked like it was coming out of the airbox tube where it connects to the top of the carburetor throat. doesn't make sense because it means the carburetor would have had to been full and overflowing but that's what it appeared to be. It ran several miles with the gas leaking and it was only after stopping and then turning the bike off and restarting I went a couple blocks and that's when it basically was flooding out and would not run. The reason I just checked the front bowl is because that's where the gas appeared to be leaking I didn't see it coming out of the rear one. I did take the main jet off and look at it it looks clean. so I just put it back in and was going to reassemble and see if it would start again. That's when I had problems getting the breather box connected back to the carb throat. so I will try cleaning that stuff off I was thinking about that sounds like a good idea.
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Last edited by Marko13; 08-09-2019 at 12:49 PM.
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post #5 of 43 (permalink) Old 08-08-2019, 02:47 PM
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ok... now its making sense

there is no way the carb filled to the brim and leaked out the top, and you then started the bike - it would suck all that gas right into the front cylinder and hydro lock the piston into the head on the first compression stroke. I know you are new but around here we obey the laws of physics :^)

More likely is your gas tank is leaking somewhere over the front carb, its dripping down on the air box, running down the inside or outside, and coming off the connection point between the airbox and the front carb.

or maybe you have a fuel line failed or the connection to the fuel filter under there, and the fuel pump is spraying gas up on the air box under the gas tank...

BTW, talk to Scrumdown about riding a mc with a fuel leak - Bertha almost burned to the ground.

Last edited by KCW; 08-08-2019 at 02:51 PM.
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post #6 of 43 (permalink) Old 08-09-2019, 12:48 PM Thread Starter
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Ok, Thanks. I'll check all those ideas. Yeah, I hadn't planned on riding with gas pouring out lol, just started smelling gas, thought it was the car in front, then after a while realized it had to be me...oops :-) Luckily it was dripping onto a little rubber coated metal "pan" that sits under the carbs and dripped onto the left side away from exhaust. ; Even so I was probably stupid to think I could drive it home after realizing the leak...luckily it flooded before exploding :-)
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post #7 of 43 (permalink) Old 08-09-2019, 01:24 PM Thread Starter
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KCW re: "if the float is stuck low in either carb float bowl there is an overflow tube that goes down just above the top of the crankcase on the right side of the bike."

The only tube I can see is a rubber 3/8ish tube that tees between the carbs and runs down to a bracket just above the engine, but it's on the exhaust side, I would think they'd want it on the opposite side, but is that the one you're talking about? It's definitely not crimped.

was wondering if I can clean the needle valve with carb cleaner as it has a rubber tip?. have melted rubber orings but that was with brake cleaner so maybe carb cleaner is different? There was the slightest yellowish tint on one side of the needle so maybe that was some build up that could have stuck even though it didn't seem to be the least bit tight when I took it apart. (always run ethanol free gas and yes, stabilized when parked)

There doesn't appear to be any leaks in the tank. There was no leaking when not running so maybe your thought of fuel filter conx though I can't see anything with the naked eye. maybe i'll put some clothes on it and try again lol.

will try to reassemble and see if i can repeat the issue if I can get that darn airbox back on ha!
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post #8 of 43 (permalink) Old 08-09-2019, 01:59 PM
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carb cleaner will be fine on the float bowl and needle valves

brake cleaner is nasty stuff

you found the overflow hose - the one you described that goes to the right side - it the float was stuck it would be coming out of that hose

if nothing is dripping with the ignition off then your tank is not leaking, it has to be a fuel line cracked or pulling off somewhere. The fuel pump only runs when the key is on and the kill switch is set to run

Its possible the gravity of the fuel in the tank is not enough to make a failed gas hose leak but when you turn on the fuel pump it starts to spray out.

you can clean that air box connection point with carb cleaner too. What you really need is someone to hold it down while you torque the screws on the clamps.

edit: that air box connection is maddening - the first time I did my valves I had no problem. The second time it took me 30 minutes to screw those two clamps down - and its the last thing you have to do, then put the gas tank back on and you are done, but nope.nope.nope.nope....

Last edited by KCW; 08-09-2019 at 02:30 PM.
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post #9 of 43 (permalink) Old 08-09-2019, 02:07 PM Thread Starter
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Yeah, I was holding it down with one hand while tightening with the other and it just acted like the throat casting was tapered, the tighter I went the more it raised up. But have cleaned now and will try again. Glad I stumbled onto this great resource! Thanks KCW
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post #10 of 43 (permalink) Old 08-09-2019, 09:30 PM
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Quote:
Originally Posted by Marko13 View Post
Yeah, I was holding it down with one hand while tightening with the other and it just acted like the throat casting was tapered, the tighter I went the more it raised up. But have cleaned now and will try again. Glad I stumbled onto this great resource! Thanks KCW
You know what we have to get is a pocket KCW so he is always there when you need him.

I ain't lost until the tank is empty!
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