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Discussion Starter #1
Howdy all, We know the Bonneville Tank is a bad design with 3/4 gallon or so fuel trapped in the RH tunnel [not sure if the Speedmaster/America has this fault] which gives a poor fuel range [under 100 miles per tank in my case]. Triumph have done nothing to fix this problem[the Bonnie has been out for 7 years now]. An easy fix at the factory would be to as HD do and fit a balance pipe to the tank, -problem solved.
A home fix should be possible, drill a hole at the bottom of each side of the tunnel, weld on a small length of metal tube and fit a rubber pipe with jubilee clips. Main problem would be welding a tank that has held gas/petrol and also ruining your nice paintwork. Has anyone done this mod?, I know there are some skilled engineers out there.
My idea for a non explosive fix is to use gas fitters or plumbers couplings. Drill the holes as before [maybe need to be bigger] slide the threaded coupling along a piece of wire into the tank and manoevre the thread out through the hole, fit sealing washers and the nuts on both couplings. A pipe could then be screwed on to each thread. The end product would be same but without sterilizing the tank or burning the paint one bit.
This is just theory at this stage, was wondering if anyone else has tried this out before I find there is some drawback why it would not work and I make a hash of my tank.
UK Daveski
 

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I'd be inclined to do something using a second stock petcock. It should be possible to just drill the tank and have self-tapping screws to attach it. That way you would have a filter. The fuel management part would have to be figured out by trial and error.
The main problem with this idea is that any leaks would be a major fire hazard.
 

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The second petcock is obviously the way to go. The old Bonnevilles had them. What COULD they have been thinking by eliminating them?

I poked a hole in the gas tank of my truck years back. Removed tank, removed all of the plugs in the tank. Flushed with water numerous times. attached an air hose to it blowing a large amount of air through the tank and while the air was blowing, welded the hole in the tank with a gas torch. No problem with unwanted fire. A similar method could be used on a Bonneville tank BUT... there is the paint job to think about as was already mentioned.

There has to be more to it than self tapping screws as the metal is too thin for me to trust that. When it comes to safety while sitting on a gas tank, no shortcuts should ever be taken.
I'm sure there MUST be some sort of design out there that would allow you to get a 3/4" to 1" flanged fitting on the inside of the tank through a 1/2" dia hole. The fitting would have to be threaded and get a sealing washer securely fitted to the outside. Its hard for me to describe what I'm thinking about without an illustration. The flange would have to be slotted allowing you to sort of 'thread' the flange through the hole in the tank.....
Or maybe after the hole is in the tank, run a piece of wire through the filler opening inside the tank and out the hole. Then slide the threaded fitting with the flange down the wire. Wiggle 'til the end comes through the hole. Apply RTV sealant through the hole and a rubber sealing washer and a nut to the outside. Attach a petcock and use an in-line filter. Just thoughts anyway.....
 

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Discussion Starter #4
The second petcock is obviously the way to go. The old Bonnevilles had them. What COULD they have been thinking by eliminating them?

I poked a hole in the gas tank of my truck years back. Removed tank, removed all of the plugs in the tank. Flushed with water numerous times. attached an air hose to it blowing a large amount of air through the tank and while the air was blowing, welded the hole in the tank with a gas torch. No problem with unwanted fire. A similar method could be used on a Bonneville tank BUT... there is the paint job to think about as was already mentioned.

There has to be more to it than self tapping screws as the metal is too thin for me to trust that. When it comes to safety while sitting on a gas tank, no shortcuts should ever be taken.
I'm sure there MUST be some sort of design out there that would allow you to get a 3/4" to 1" flanged fitting on the inside of the tank through a 1/2" dia hole. The fitting would have to be threaded and get a sealing washer securely fitted to the outside. Its hard for me to describe what I'm thinking about without an illustration. The flange would have to be slotted allowing you to sort of 'thread' the flange through the hole in the tank.....
Or maybe after the hole is in the tank, run a piece of wire through the filler opening inside the tank and out the hole. Then slide the threaded fitting with the flange down the wire. Wiggle 'til the end comes through the hole. Apply RTV sealant through the hole and a rubber sealing washer and a nut to the outside. Attach a petcock and use an in-line filter. Just thoughts anyway.....
Thanks for the advice, I did not think of a second petcock route, it sounds easier than the balance pipe method. I am still thinking along the line of gas or plumming fittings as has been mentioned self tappers could be a bit dodgy. The hardest bit could be joining the 2 petrol pipes. Small diameter standard pipe, spliced to a larger diameter gas pipe. I am not sure how small gas/plumming fitments go, I will ahve to check out what is available before I go any further.
 

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I haven't had one apart, but if the tank-to-petcock gasket is outside of the screw fittings then you could use riv-nuts as used for door mirrors etc. They come in pretty small sizes but don't seal fluids very well. If they are within the gasket then it would't be a problem.
 

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We know the Bonneville Tank is a bad design with 3/4 gallon or so fuel trapped in the RH tunnel [not sure if the Speedmaster/America has this fault] which gives a poor fuel range [under 100 miles per tank in my case]. Triumph have done nothing to fix this problem[the Bonnie has been out for 7 years now]. An easy fix at the factory would be to as HD do and fit a balance pipe to the tank, -problem solved.

A home fix should be possible...
Here's my fix.

1) after hitting reserve & riding a bit, I lean the bike to the left when stopped at a traffic signal.

2) Upon resuming forward motion, I return the petcock to the normal postion.

3) Repeat.

4) Stop for gas when the above routine grows tiresome.

Cheers,

--Rich
 

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3/4 gallon mystery

Could someone please explain about the tank. You run out ot fuel and switch to reserve. Is that the 3/4 gallon in question? Or is there an additional 3/4 gallon lurking around unused?
 

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If you look at the tank it straddles the frame thereby having a section either side of the frame that contains fuel. The petcock is at the bottom on the left section. Once the level in the tank drops below the height of the frame the fuel in the right section will not flow into the left side thereby being inaccesible. The reserve is all to do with the petcock plumbing. In an emergency you can tilt the bike over to the left far enough for the fuel in the right section to flow over into the left section. The discussion is about fitting a tap in the bottom of the right section to allow the fuel to flow across freely.
 

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Does this mean I should just get a turkey baster (with a flex-hose) and use it to suck up the right side and squirt it into the left side, when I need a reserve on my reserve?
 

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Yeah, you could do that, but at the risk of being called a bastard.
 

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Seems like a lot more trouble than it's worth.

On long trips where fuel availability may be questionable, I make sure I've got a socket or spanner of the appropriate size with me so that - worst case scenario - I can pull the seat and dismount the tank (two bolts) to roll it to the right and slosh the fuel over (no need to disconnect the fuel hose). Slightly more time consuming, but safer and more effective than trying to tip the bike over far enough to get it all.
 

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I thought about the same thing. Just a 1/4" fitting on each side of the tunnel with a hose connecting them would be sufficent. I thought silver soldering would work, strong but still too hot to save the paint, or my perfered process TIG. I welded on a fuel tank just last summer. Flushed it with water many times, put a running air hose for a long time and left in the sun forever. Still was scared, but came out okay. May try it this winter, planning on a paint change anyhow. Seems a shame to not have the range. Would be so simple for the factory to fix.
 

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I don't understand why people keep talking about welding. What about one of these:



Seals on both sides - designed for fuel.

All you would need to add would be an inline valve or something.
 

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Am I being thick?

I don't understand why people keep talking about welding. What about one of these:



Seals on both sides - designed for fuel.

All you would need to add would be an inline valve or something.
How do you tighten the part in the tank?

Cheers,

SK
 

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The fitting that Pokeyjoe is showing is an Aeroquip bulkhead fitting used on aircraft and commonly adapted to race cars. With Teflon washers, it would make a good seal. They are made from anodized aluminium and would not rust or otherwise contaminate the tank. The only drawbacks that I can see is installing it and tightening the nut with a back-up wrench. Also, the flare end is 37 degrees instead of the usual 45 degrees found on plumbing type fittings. This would require a special flaring tool, if you wanted to put a tube nipple on it for a hose. Maybe a Swagelock brand of bulkhead fitting would work more easily.They come in Stainless steel or Brass and have a replaceable ferrule, just insert the tube and tighten the nut to crimp it. ( no link, but I'm sure you could find it on Google)

If you want to weld on a gasoline tank safely, it should/must be purged with Argon, Nitrogen, or Carbon Dioxide, just eliminate the Oxygen. After pouring out all the gasoline possible, let the remainder dry with the filler neck open. The poor man's way is to drop small chunks of dry ice into the filler neck, as the solid sublimates into Carbon Dioxide gas it will displace the air and make it safe to weld. This way you don't have to contend with eliminating the water from trying to wash the gasoline out. I personally have used this technique to weld an aluminum tank that had held gasoline, just don't be stingy with the dry ice. I can't help with the burned paint job though.----James.
 

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I think I recall seeing a yellow Bonnie somewhere online that had a second fuel tap installed on the right side of the tank. It might have even been on this site.
 

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Discussion Starter #20
How do you tighten the part in the tank?

Cheers,

SK
That fitting looks just the job. I find 'blind' nuts where you cannot get a spanner to often can be tightened by 'pulling' on the accessable nut while tightening it. The inner nut will often grip on the metal enough to get some friction to allow it to be tightened.
Where can I get some of them?.
UK Daveski
 
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