Tanks

[tinman905]

Can anyone tell me is there a difference between a 81 Sp tank and a 80 Sp tank . I thought they were the same but the one I received doesn't have a fuel sensor , the person I bought it from said it was for a 81 Sp.

[John]

They are the same tank. If the tank you have does not have a sender in it, then it may be from a 750-850 Special. They look similar, but the 11's tank has a dimple in the bottom seam to clear the valve cover, and the front mounting pockets are in different locations.

[ExcessiveBiker]

Tank change

Just put a standard tank on my 81 special, with a few mods to make things work. My problem is the low fuel warning light works backwards. When the tank is full, the light is bright. When the level approaches reserve, the light starts to dim.
What gives??????
thanks,
EscessiveBiker

[TopCatGr58]

Hey Excessive,

The problem is the fuel sender unit for the Standard uses a float system with variable resistor for the actual gauge. You can just swap out the sender from the old Special tank into the Standard tank, and then your light should work just fine.
T.C.

[Do Lee]

Excessive,
I've been running my 79 Special for years with a Standard tank and I'm using the sender from my old Special tank but it upside down because the Standard tanks sender hole is on the opposite side so your reserve level sender tip is lower than normal about half a gallon or so. I'm getting 155-160 miles when I need to go to reserve and 175-180 miles before the light starts to light-up and 195+++ starts sucking fumes and dies and this is ideal running conditions. Only done that once. I log all my fill-up and try to full-up around 150 miles or so witch is normally 4.3 to 4.7 gallons. Once you log your trips with the bigger tank you really won't use the fuel light. Your numbers will very.

[DJinNH]

Originally posted by John
They are the same tank. If the tank you have does not have a sender in it, then it may be from a 750-850 Special. They look similar, but the 11's tank has a dimple in the bottom seam to clear the valve cover, and the front mounting pockets are in different locations.

Well I am sure relieved to see you wrote they are the same, John. This topic had me worried when I first started reading. I just had both tanks painted and like the candy red better than the maroon. Since I already put the triple tree that was painted maroon (because it was rusted) on my SH, I sure as heck didn't want to have to change it back to the SG all over again.



Don

[fredintoon]

Inverted, eh?

Hi Do Lee,
I'm in the middle of swapping a Standard tank onto my Special and I will also be keeping the Special's fuel sender to retain compatibility with my Special's instrumentation. The thing is, I'm used to seeing that red low fuel light turn on 10 miles before the bike goes onto reserve. 10 miles after it goes onto reserve it runs out of gas. Having the red fuel warning light come on then is superfluous because when the engine stops the red low oil pressure light will come on anyway.
You say you put the Special's fuel sensor in the Standard tank upside down "because it's on the other side of the tank"? Could you not have extended the signal cable a little and put it on hind side foremost instead? And would that have made a difference to the fuel level that the Special's sender works at? While I can understand how the Standard's sender works with it's little float arm and all, I have no idea about how the Special's sender works. Can anyone tell me?

[John]

Fred, the sender in the Special is basically a resistor that heats up when uncovered by the fuel, therefor completing a ground circuit, causing the light to come on.

[fredintoon]

Hi John,
According to Do Lee's post, the Special sender doesn't switch the red warning light on until 15-20 miles after the Standard tank has gone onto reserve and once the red light is on the bike will go a further 15-20 miles before it actually runs out of gas. OK, I can live with that. But Do Lee also says he installed the Special sender upside down (presumably because that's the way the wiring pointed when it was on the other side of the tank) My next question is, does the Special sender operate at a different fuel level if it's upside down?

[John]

Fred, the resistor that is used is not very long at all. When my low fuel light comes, I have about 5 miles before I need to switch over. I don't know if the opening in the Standard tank is located in a different level than the Special tank, but that could be the case.