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Message started by trapper_canada on 06/27/09 at 15:12:15

Title: Quick DUMB carb question
Post by trapper_canada on 06/27/09 at 15:12:15

Looking down at the carb from above there are two black hoses coming out of each side of the carb. They are the same length.

Do they go anywhere?

I pulled the carb and didn't notice if they went anyplace. Are they just breathers? If so..where should they be routed???

Title: Re: Quick DUMB carb question
Post by Boule’tard on 06/27/09 at 15:15:21

Yep, just breathers. Tuck them into the frame channel above the carb.

Title: Re: Quick DUMB carb question
Post by trapper_canada on 06/27/09 at 15:30:59

515C465F5647524157330 wrote:

Yep, just breathers. Tuck them into the frame channel above the carb.

Awesome! Thanks.

Title: Re: Quick DUMB carb question
Post by Gort on 06/27/09 at 15:46:30

The hoses will release fuel in the event of bowl overflow. It happened to me. On emission spec. bikes, they connect to a charcoal canister at the bottom of the bike, so as to stop gas from being released into the atmosphere. I removed the charcoal canister on my bike, and when I had a bowl overflow issue, those hoses dripped fuel onto the ground. Mine were long enough to be easily routed to the ground, but if yours are too short to make it to the ground, I would replace them with ones that will. You don't want fuel trickling down onto a hot engine/exhaust.

Title: Re: Quick DUMB carb question
Post by Boule’tard on 06/27/09 at 17:17:21

That's not a bad idea, but don't go straight from the carb to the ground. Sure, the gas would drain to a safe place, but is far more likely to spew out in the first place. You can get the best of both configurations by routing the hoses as high as they would normally go in the frame channel, then to the ground. If you don't do that, the frame channel will direct any spillage behind the cylinder, not on your header or anything super hot. Should be ok if you keep the Rubber Side Down :D

Title: Re: Quick DUMB carb question
Post by Gort on 06/27/09 at 18:02:16

Fuel spews out the hoses because the bowl float is stuck open. When the bowl overflows due to a stuck float, the height of the hoses is irrelevant. As long as the bike is running, the bowl will empty itself through the hoses until the engine is off or until the gas tank is empty, because the tank is higher than the bowl and frame, and has a pressure head. The only solution is to resolve the stuck float issue. Routing the hoses up along the frame channel will distribute that fuel everywhere, especially if the float sticks when you are driving forward through the air. These hoses need to be aimed at the ground, or directly down into the charcoal canister, if you have one.

Title: Re: Quick DUMB carb question
Post by Boule’tard on 06/27/09 at 18:56:05

Ooh I just love debating the finer points with Gort! [smiley=happy.gif] And trapper_canada thought he had a dumb question.

It does indeed matter how high you route the hoses, because the lobes of the tank are below the frame rail so that the level in the tank is below the end of the vent lines much of the time. Not all of the time (I think the bottom of the filler neck is above the frame rail) but a stuck float would never cause the tank to empty out of the vent hoses.

The other thing is, the vent hoses as routed by the factory would pressurize the bowl to 3 or 4 times the normal head before leaking gas, and I serously doubt the engine would run under that condition. I don't know that for sure though, so will trust the engineers on that point, then my own ability to shut it down when it's running poorly, and failing that, at least these bikes aren't known for spontaneous combustion. ;)

Original design ..good
Routing straight to ground ..worse
Routing up then to ground per Gort's idea ..best. I'd do it that way if I wasn't about to change carbs.

Title: Re: Quick DUMB carb question
Post by Gort on 06/27/09 at 19:12:59

Indeed, a good technical discussion with you is most satisfying, and after considering the 4 to 5 times pressure issue you pointed out, I must agree with you.

One fine thing about this site as compared to every other cycle site I've visited, is that newbies have a wealth of information at hand, if they just visit everyday. And for the few site support dollars it costs to become an Alliance Member, they have access to even more info, including Sluggo's porno collection.

Title: Re: Quick DUMB carb question
Post by trapper_canada on 06/27/09 at 19:15:44

Thanks for the info. I ended up having them going up and then it curls down a bit...but if I go spewing gas it will end up splashing on the big rubber tube between the carb and the cylindar.