Gravity or siphon gas line

Discussion in 'Motorized Bicycle General Discussion' started by scribling, Feb 12, 2015.

  1. scribling

    scribling New Member

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    Would it work having a gas line through the top of a tank using a siphon to move the gas rather than gravity out the bottom?

    I've broken 6 gas tanks now and I'm sick of it. I'm thinking of using a thermos or something like that with a siphon tube through the cap rather than a bung in the bottom.

    Maybe I'll test it. That may be quicker ...

    Thanks
     
  2. Flyman

    Flyman New Member

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    You need gravity feed unless you are running a diaphragm pump or pumper carb run off crank case compression.
    What,s breaking on your tanks?

    Fly
     
  3. KCvale

    KCvale Active Member

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    I am curious as to how you keep breaking gas tanks too.
    6 of them? Really?
    What are you building with, $99 E-pay crap kits?
     
  4. scribling

    scribling New Member

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    Yes, I'm up to six broken tanks. The rivets keep breaking. First, I mounted the tank as it should be, those rivets cracked and leaked. New tank same mount, crack, leak. I figured I'd reinforce a new tank with JB Marine Weld in and out. I let it dry for two weeks. JB Marine Weld claims to be petrol proof, but it is not. When the rivets broke, I looked inside, not a trace of the JB Weld remained. Next, I devised a new mounting system that didn't put pressure on the rivets but used them only to mount a bracket, I thought that was genius but the rivets still broke. I got a better quality tank that's smaller ... and it broke. These Chinee tanks are crap. They're made out of literally paper thin scrap metal.

    I also tried the rear, rack-mounted tank but that idiotic thing is engineer by a retard. The filler and bung are at the same end. So, if you fit it so you can get to the filler, at the rear, your gas line has to be 2.5' long; and if you mount it so the bung is close to the engine you can't open the filler because it's under the seat. Not to mention the tank doesn't fit the rack and the rack doesn't fit the bike and either configuration the tank gets in the way of the brakes. I seriously don't think this tank and this rack were ever meant to go together. I think they hate each other and refuse to work together.

    So now I've got the rear rack mounted tank zip tied where a normal tank would go. I have two upper tubes so it's stable at least, although it looks stupid.

    I have a straight frame, no shocks at all. Every time I go off-roading I break a tank. I'm not hitting huge jumps or anything, just dirt roads. Ok, maybe a couple jumps ... once in a while.

    I've seen a guy on a bike with a vertical, thermos looking tank that looks really cool but I can't find it online anywhere. He said he'd sell me one for $100, but I know he's not making them. So, he's getting them somewhere ...
     
  5. 2door

    2door Moderator
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    Lots of idea and discussion here > http://www.google.com/cse?cx=partne...gsc.tab=0&gsc.q=mounting fuel tank&gsc.page=1

    If you do off-road, rough riding you're going to have to find a way to cushion the tank from the frame and not rely on over tightening the studs to keep it in place. There have been many suggestions for this posted here. Thick rubber, cushioned double sided tape. automotive window glass mounting tape, silicone adhesive, etc.

    The biggest cause of stud/tank failure is over tightening of the stud mounts. This is exacerbated by rough terrain, curb jumping and bike frame abuse.

    Glue, epoxy based repairs usually don't last, if they work at all.

    Tom
     
  6. scribling

    scribling New Member

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    Yes, well my tanks were insulated from the frame with 1" foam cut from a kid's pool noodle.

    My mount that shouldn't have put any stress on the rivets should have worked great. I think it was just vibration that breaks these pieces of junk.
     
  7. mapbike

    mapbike Active Member

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    spray channel on bottom of tank with rubberized under coat like you find in the auto parts store, do the eame on the straps, do not overtighten nuts, use blue loctite on threads or double nut, key here is just enough force and grip to hold tank in place and not o r
    ertightening nuts.

    ive had one tank in 5 years leak at one of the studs, it was one of the junk chrome tanks and i had overtightened the nuts.

    i ride very rough dirt roads and my bikes take a beating and i have no problems breaking tanks off ebay or anywhere else.
     
  8. Davezilla

    Davezilla New Member

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    ^^ What map said...
    Having too much vibration insulation can be worse than none at all... What happens here is you stil got the vibration from the road to deal with, but with too much or too thick of insulation it viges the frame and the tank a "running start" before they contact or pull on the bracket etc, and this accelerates wear exponentailly to say the least.

    There are several methods to get it "just right" and your tank will last as long as your bike does... I use an old grip cut in half and glued to the top of the frame then I just bolt the tank onto that and Snug it down, just enough to where the tank won't move and that's it... A drop of locktite keeps the nuts from backing off and it hasn't failed me yet... I do most my riding on pavement but there are the occasional potholes and rough driveways to deal with.

    Other people have successfully used a piece of cut up inner tube, double sided tape, a few coats of that Flex Seal stuff on the top tube, undercoating, old gel grips cut up, etc. The idea is to insulate it from vibration and hard bumps, but it needs to be thin.. like 1/8" or thinner is all you need.
     
  9. KCvale

    KCvale Active Member

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    I use BMX foam grips on all my builds so there is always a little excess, I just us 2" wide strips of it on the top bar between both tank studs, and with 80 some tanks used only over tightened one enough to crack a stud free, Marine JX fixed that.

    You keep saying rivets, what rivets?
    The top and bottom haves are spot welded together all the way around, is that what is breaking? or is it the studs?
     
    #9 KCvale, Feb 13, 2015
    Last edited: Feb 13, 2015
  10. scribling

    scribling New Member

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    Studs, yes, that's what's breaking. Rivets is the wrong word.

    I tried small amounts of insulation first, inner tubing, pipe insulation ... before going big time to half pool noodle. Some isn't petrol proof and would just disappear. Hey, where'd it go? Oh, here's a tiny bit of it ...

    These tanks are literally paper thin. Ok, maybe 5-10 sheets of 20lb paper ... either way they're ridiculously thin. I have a hard time believing I'm the only one breaking them.

    BTW, these animated icons below remind me of a joke. The first day in prison at dinner time an inmate stands up and says, "Six." Everyone laughs. Another inmates stands up and says, "Twenty four." Everyone laughs. The new guys says to the guy next to him, "What's so funny about numbers?" "Well, we've all been in here so long that we all know the same jokes. So, we gave them numbers. Now, instead of telling the joke we can just say the number." So, the new guy stands up and says, "Fourteen!" Nothing ... No one laughs. He whispers to the guy next to him, "What happened?"
    "... Some people just don't know how to tell a joke ..."

    The point is we've all seen these icons and we're probably not impressed with them ... so just give them a number ... 4
     
  11. Rudz

    Rudz New Member

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    I used pieces of an old leather belt to cushion my tank and only snug it down. I already cracked the studs on my big 4L tank. I'm not made of money, I can't buy new $20-30 tanks every month, so I used the stock kit tank.

    Going to try and fix my bigger tank with water weld, of it works, good, if not, Oh well.
     
  12. scribling

    scribling New Member

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    I can tell you JB Marine weld will simply dissolve in petrol. No use what-so-ever.
     
  13. fatdaddy

    fatdaddy New Member

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    Getting back to your original question, If you have ever used a hose to steal gas from yer moms gas tank for your mini bike when you were a kid, then you know how it works. It will still be gravity feed, kinda, but just the gravity and suction from the hose you use. BUT, theres GOTTA be a better way bro. Maybe try yer rear tank on another rack. I do a lot of rear mount tanks and they seem to work well for the most part. I've also had the same stock tank on my bike for almost three years, no problems. knock on wood.LOL
    fatdaddy.usflg
     
  14. Trey

    Trey $50 Cruiser

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    fatdaddy's right. There's gotta be somethin. This is what mine looks like; http://motorbicycling.com/showthread.php?t=48562
    I put a piece of rubber hose under the tank where the tube would be, and all I have to do is check the tightness once in a while. Works far better than I expected.
    Gravity seems to be best with the majority of these set ups. There are carb options, as has been said.

    Hope this helps.
     
  15. fatdaddy

    fatdaddy New Member

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    A good friend of mine, Ocho ninja, Uses the Predator engines a lot but dont use the gas tanks that come with it. So a lot of the builds that come out of my shop have tanks that say predator on them. the 212 comes with a good size tank. they mount well to a rear rack. I dont recomend buying a predator engine just for the tank though.LOL
    fatdaddy.usflg
     
  16. Davezilla

    Davezilla New Member

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    He can buy the engine then take the tank off and send the engine to me, that way both pieces will be put to good use...
     
  17. scribling

    scribling New Member

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    I wouldn't be opposed to buying a new engine. Mine is so out of balance it's like riding a jackhammer. The vibrations are so bad at top speed I literally cannot hold the handle bars tight. Yes, I have dampeners on the frame mounts.
     
  18. 2door

    2door Moderator
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    There's your problem. If you are using any kind of rubber or resilient material between the engine and the frame you are increasing vibrations, not decreasing them. This explains why you can't hold onto your handlebars and probably why you keep breaking fuel tanks.

    It has been proven time and again that you can't mount the engine in rubber and expect not to get excessive vibration. Get rid of your "dampeners" and mount the engine as solid to the bike frame as possible. I won't get any argument from any experienced builder here.

    Tom
     
    #18 2door, Feb 14, 2015
    Last edited: Feb 14, 2015
  19. boxcar

    boxcar New Member

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    Yea , you will.
    I run a dampener ( not rubber ) system of sorts and all my bikes are as smooth as silk.
    Try copper tubing spacers between the clamp and the head of the studs.
    Eliminates the stress on the sheet metal the studs are welded to.....

    [​IMG]
     
  20. Trey

    Trey $50 Cruiser

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    Read this. It is the answer.
     

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