General Aux Fuel Specs that never seem to go out of date


Active Member
All: Add to this list of fun as you can.

1- IF your filler cap is not easily replaced buy a purchase at the nearest NAPA, TETHER the cap (Thanx to famed rider Dave E.B. Smith). Having a spare cap w/ replacement tether buried in your kit is not overkill.
2- Those odd-looking 3.5gal aluminium tanks from Summit Racing are rarely more than 3.25gal. Beware that they vary. IF you want to know exactly how much they hold, plug the outlet and fill at the local gas station. Note the capacity on the tank or as you will.
3- Said tank, as above, has a check-ball/valve in the vent to block spillage at a tip-over. The ball likes to rattle until it doesn't. When it doesn't, the ball likes to jam in the valve seat. This causes the vent not to. Thus gravity feed may not work because the draw on a 5/32" hose is not strong enough to pull the ball free. Do not panic when/if you notice that your fuel gauge is not going up. Find a safe place to stop and open the filler cap. That releases the vacuum and fuel should drop in the tank as the main fills. Taker a convenient rock or maybe your handy multi-tool and give the check-valve a slight tap/rap to knock the ball loose. Replace tank cap and note if fuel is still being transferred. Eventually, the ball will beat up the seat enough that it won't get stuck...very often. Some riders remove the ball and pig-tail the vent ...or not.
4- Said tank, as above, is not nearly as sturdy as one might think if being dragged along a gravel road for a surprisingly short distance. (Don't ask how I know this. I too was very much surprised at how non-sturdy it turned out to be.) No, I cannot guess how the poly tanks fair to the same abuse. Now that I know this, I wonder how it can be sold as "racing" spec? Now that I know how bad it is, I would hate to be in a spectacular racing wreck with that thing on board. My next aux tank is likely to be a poly as it surely can't be any less sturdy?
5- IF your aux tank is mounted high and over the tail piece AND you can engineer the bike to run the aux fuel dry FIRST, do so. If you can't, note that moment on your main tank when you can open the aux tank and transfer the fuel to the main as soon as possible. Assuming that one decides that an empty aux tank back there is safer than a full one? Or a partial?
6- Aux fuel mounted over the tail piece is way...out there...and will suffer larger/stronger harmonics in the mounting tabs as well as the mounting frame/structure. Some over-engineering here is a good thing. And frequent inspection for stress fractures is not overkill nor OCD. I put some poly " vibe dampeners" under "said tank" and still broke all 4 mounting tabs on the gravel roads of the Far North (Dempster, Campbell, etc). Granted said tank worked well on pavement for a few previous years and gave me false confidence that it would hold up to serious gravel. IF...I was to do such a thing again, I would engineer at least 2 "over-straps" and place some sort of "full footprint" dampener pad (old computer mouse pad?) between it and the support frame/deck. N.B. 3.5gal+tank+mounting hardware=30lbs+? That's a lot of weight to be buzzing away out there. Figure that you are going to stress/vibe fracture the tabs no matter what might be engineered right from the start. Even if the bike is only going to be used on pavement, how many serious chuck-holes can that hardware take before weakness shows up? And it is cumulative. Thus frequent inspection, like every pre-ride and post-ride, is not OCD.
7- I had a 4gal Rotopax "lashed down" and thus not 'plumbed-in' that worked fine on am similar AK trip. From my POV, transporting aux fuel as a 'lash-down' just so one does not have to worry (2gal?) could be the hot set-up? Check your rally rules before you decide to go thru tech. Plumbed-in is sure fun to have but not always ideal for what needs to be done. If one is going to do this, check that the cap really does seal in all positions.

ps: This place says that I am a 'new member'. For who knows why, when the site changed over a few years back; all my stuff got deleted and I couldn't get back on w/o a 'new join'. Gotta luv this digital fun. Story Time: While traveling in the Far North with 2 biker budds each carrying lash-downs, one stopped to inform us that he was never going to make the 30+ miles to the next fuel and had 'forgot' to fill his lash downs. The other budd had not fueled his lash down either. I let them jaw about a minute about how we were going to solve this fuel issue. Then I teased 'em,,, mercilessly. My bike at the time was plumbed-in. So I got one of their lash-downs and filled it from my aux tank "tee" engineered just so I could do such a thing... at a saunter.... and w/o fuss. Told 'em that I had put enough fuel in my aux system way back in the States so that I could keep an eye out for any leaks in my system AND for moments just like the one that we were having. Bwah-ha-ha... FYI: If a rider worthy of this web site isn't already carrying siphon equip for helping other road users, maybe such a rider might rethink how s/he does things?
Your Fun May Vary,

pps; Luv ya and miss ya, torqueman, wherever you are.