Gas tank venting

Peckerwood

Active Member
Sum BITCH!!! I think it's that crappy HD cap after all. Tried sucking of the cap again, and it won't vent with easy pressure, only hard. Heading to the dealer again to check out that new one. Thanks again for the help and suggestions, I'll let you all know how the ride goes.
 

HMAN

I just like my Freedom
Supporting Member
FWIW, here's what I did on the Pit with dual tanks. Where the crossover tube is under the dash, I cut it in half and installed a tee. Then ran a line to the rear downtube and straight down till the line was just visible under the bike. ALWAYS have positive ventilation then. Just my .02
 

Dragonslave

Active Member
FWIW, here's what I did on the Pit with dual tanks. Where the crossover tube is under the dash, I cut it in half and installed a tee. Then ran a line to the rear downtube and straight down till the line was just visible under the bike. ALWAYS have positive ventilation then. Just my .02
This is what I did with mine also.
 

chubs

Guru
If the tank builds pressure when the gas heats up in the sun, wouldn't that also put extra pressure against the float and hold it shut? Seems like you would want the vent to work both ways. :oldconfused: :oldconfused:
 

Th3InfamousI

Administrator
Staff member
FWIW, here's what I did on the Pit with dual tanks. Where the crossover tube is under the dash, I cut it in half and installed a tee. Then ran a line to the rear downtube and straight down till the line was just visible under the bike. ALWAYS have positive ventilation then. Just my .02
T pointing up, yes? Otherwise you'd be losing gas?

Sent from my 831C using Tapatalk
 

Peckerwood

Active Member
I just needed to say all y'all are great people. Thanks for all the help. And, after all, it was the fuckin' Motor Company OEM gas cap, vent was partially plugged. I did the ride and the Dog ran great, an important one for one of my friends who had complications from dropping his bike (hospital acquired infection that almost killed him). We must have had 300 bikes. 200 miles, no problems, except for the fact that I'm getting too old to ride a soft tail. I feel like I went a few rounds with Mile Tyson. I like the idea of the T fitting. Hope I can return the favor some day.
 

Hirter6Pack

Not Quite A Guru
This has nothing to do with the gas vent except that my overflow tube is not capped, but it has everything to do with the power of the pack.
Let me tell you all a little story, it's a true story. I was going to call it the sales man but since were on the big dog biker lm to call it the power of the pack. When l was a whole lot younger we lived on a farm east of town. I had two dogs, a mutt and a German Shepherd. It was my job to feed the cows every morning and every night after school. The dogs we're always there helping. One evening after school while we were feeding the cows we noticed a car coming up the gravel road slowing down to turn in the lane. The dogs took off towards the house one went one way and one with the other. I had to put the feed buckets away. when I came out of the barn The dude has gotten out of his car. The mutt right in front of him barking. The dudes eyes were wide open not moving a muscle except for one eye that looked at me. Then the dude hollered at me. He said is that dog gonna bite me. I said that's not the dog you have to worry about its the one sneaking up behind you that's going to bite you in the ass. That dude stood there for one more second before he made a leap to his car and just got the door closed before both dogs were right there at the door. That dude took off back down the road. with both dogs running after him barking one over the other. We never saw that dude again. I think he was a salesman. That is the power of the pack, always working together.
Good Jo's getting another one back on the road.
:old2::chopper:
 

Srodden

Well-Known Member
If the tank builds pressure when the gas heats up in the sun, wouldn't that also put extra pressure against the float and hold it shut? Seems like you would want the vent to work both ways. :oldconfused: :oldconfused:
No ! It's a float not a valve
 

chubs

Guru
No ! It's a float not a valve
Granted it is a float, but with the higher pressure in the bowl, I believe it can actually hold the needle seated. Why would, with the tank being pressurized and the bike not run, but when the pressure is relieved it runs fine?
 

Th3InfamousI

Administrator
Staff member
Granted it is a float, but with the higher pressure in the bowl, I believe it can actually hold the needle seated. Why would, with the tank being pressurized and the bike not run, but when the pressure is relieved it runs fine?
Because the high pressure in the tank was creating a vacuum not allowing the gas to actually leave the tank to fill the carb.

Think about your plastic lawnmower gas can in the shed. When the air hole on the opposite end of the spicket is closed it barely dribbles out when your trying to fill your mower. Take you an hour to get a pint out.

Pressure always has to remain equalized as gas leaves your tank air fills it up.

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chubs

Guru
Because the high pressure in the tank was creating a vacuum not allowing the gas to actually leave the tank to fill the carb.

Think about your plastic lawnmower gas can in the shed. When the air hole on the opposite end of the spicket is closed it barely dribbles out when your trying to fill your mower. Take you an hour to get a pint out.

Pressure always has to remain equalized as gas leaves your tank air fills it up.

Sent from my 831C using Tapatalk
Okay , my bad! I was of the impression the tank was building pressure sitting in the sun and causing the problem. I understand the concept of the vacuum, and agree with ya on that point! :old2::cheers:
 

chubs

Guru
going back to the beginning and reading again, in post #6 he states that after setting in the sun for a while, "there was a LOT of pressure" pressure doesn't create a vacuum, but instead will negate it. Your example of the gas can Shows what a vacuum will do to the flow, but now lets hook a hose to that little vent hole and pressurize the can. It'll empty out in no time! I still think the float needle was being held closed by the pressure difference. (But I do respect your opinion :cheers: ) Stay Safe!
 
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