Main fuel tap standpipe

Status
Not open for further replies.
Joined
Feb 7, 2010
Messages
4,195
Country flag
Can anyone tell me what the purpose of this is? Drained the Titanic's tank to put in some fresh 93 octane no-eth and I noticed more than an inch of fuel (a quart or so) left in the right side of the tank, while the left side (reserve) was completely drained except for a trickle left where the top of the tap stands proud of the bottom of the tank. The standpipe doesn't appear to be taller than the rear of the tank tunnel, so no way for any of that fuel to get into the lines. Unless there's a good reason I can't fathom, the pipe has got to go.
 
Thanks, Les. I don't believe that removing the pipe could somehow affect reserve capacity and I don't ever want to have to desperately tilt the tank. I can see where some of the fuel from the right could splash over to the reserve side in motion, but it has to be minimal. I got more than 2 1/2 gallons out of the main tap and another 1/2 gallon from the reserve, so there was at least a quart of fuel that can't be utilized.

I know you can run it either way, but I've always put the main tap on the right and the reserve on the left so it could e easily opened while rolling when the carbs start sucking wind. If you run out and for some reason you can only get a small amount of fuel (not enough to make much reserve) I would prefer to be able to use it all.
 
Last edited:
FWIW - on my Fastback tank I discovered the same thing. On my FB tank, once the fuel level drops to a certain point, there are essentially two separate fuel tanks with no 'connection' between them under normal conditions. So I installed reserve petcocks in both sides and use the right side as the main and the left as the reserve. Works great - there is a bit over 3 quarts of fuel left when I open the left side.

Don't know if the same sort of tank 'separation' exists on Roadster or Interstate tanks.
 
I don't believe that removing the pipe could somehow affect reserve capacity and I don't ever want to have to desperately tilt the tank. I can see where some of the fuel from the right could splash over to the reserve side in motion, but it has to be minimal. I got more than 2 1/2 gallons out of the main tap and another 1/2 gallon from the reserve, so there was at least a quart of fuel that can't be utilized.

Draining the tank statically, the amount of trapped fuel will be more than if you were riding.
If you fit two reserve taps to a Roadster tank then don't expect to get too far on that 'reserve' fuel supply.
 
Draining the tank statically, the amount of trapped fuel will be more than if you were riding.
If you fit two reserve taps to a Roadster tank then don't expect to get too far on that 'reserve' fuel supply.

I don't expect to get really far even on a full tank.
I know what you mean though as fuel splosh will reduce the theoretical amount from no difference to less.
 
The tank shape is different but 2 reserve taps on a 1969 TR6 home market tank will give you a reserve of 1/4 mile, luckily I was on the top of a hill with a filling station at the bottom. A standpipe got added when the tank was low again a couple of days later.
 
I've done about 10 but I found a garage before I ran out.
I feel an experiment coming on...
 
Draining the tank statically, the amount of trapped fuel will be more than if you were riding.
If you fit two reserve taps to a Roadster tank then don't expect to get too far on that 'reserve' fuel supply.

I wouldn't deny that, but I having unused fuel in the tank won't extend your range. Quite the opposite.

I've always done static drain tests on my bikes just to get an idea of the capacities. Many riders have no clue about their actual fuel range or mileage and some (my Harley-riding buddy) freak out when they hit reserve because of that ignorance. If I rode these old crocks any distance, I'd run 'em down to empty while carrying some spare fuel to see more precisely how far they'll go. I know
because of the tank shape, the SS clone has a very small reserve. The Titanic's Roadster tank is baffled and I assume that's to minimize splash and keep the fuel on the side it started on.
 
I have two like that, but with a pretty precise gauge on my KTM, I know when the light starts flashing, I have a gallon (40 miles) left.

I rode the ZX-14 down to fumes once in Oklahoma, getting 10-15 miles more than I thought I could and when I filled it up, it took 6 gallons to fill the 5.8-gallon tank.:oops:
 
but I having unused fuel in the tank won't extend your range. Quite the opposite.

I wasn't suggesting it would extend the range, with two 'reserves' you will travel further on 'main' supply and not so far on 'reserve' but with the stand pipe it's easy enough to lean a relatively light bike like a Commando over far enough to slosh the trapped fuel to the reserve side. Edit: Or, remove the tank and tip it.
 
I've done about 10 but I found a garage before I ran out.
I feel an experiment coming on...

That experiment then:
Roadster tank fitted with two reserve taps, I run the right hand side tap normally with the left hand tap being my "reserve reserve"
I ran the bike on A and B roads with plenty of turns and stops to get some splosh over from left to right whilst it was running down on the right hand side.
First falter I switched the left tap on and pulled over to take a picture.
Set off again until it ran out, second picture.
As I knew I had about three litres of fuel tucked away behind me I wasn't being frugal so I "might" have got slightly more mileage.
Result: A tad under 9 miles.
Main fuel tap standpipe
Main fuel tap standpipe
 
Last edited:
That experiment then:
Roadster tank fitted with two reserve taps, I run the right hand side tap normally with the left hand tap being my "reserve reserve"
I ran the bike on A and B roads with plenty of turns and stops to get some splosh over from left to right whilst it was running down on the right hand side.
First falter I switched the left tap on and pulled over to take a picture.
Set off again until it ran out, second picture.
As I knew I had about three litres of fuel tucked away behind me I wasn't being overly frugal so I "might" have got slightly more mileage.
Result: A tad under 9 miles.
View attachment 11059 View attachment 11060
Cool! Now we need you to do it, exactly same run, with a standpipe setup to see what difference it makes ;-)
 
Cool! Now we need you to do it, exactly same run, with a standpipe setup to see what difference it makes ;-)

It shouldn't in theory be different, however there would be some fuel left in the standpipe side to splosh over to the reserve side.

...and, no, I'm not going to prove it.
 
It shouldn't in theory be different, however there would be some fuel left in the standpipe side to splosh over to the reserve side.

...and, no, I'm not going to prove it.
One question, Nate, was the tank baffled or no?

The owners manual for the Simplex Servi-Cycle (1935-1952 divided tank, one petcock) advised the owner who had run out of fuel to lay the bike on it's side to allow the half-gallon on so on the opposite side to slosh over to the side with the petcock and be on your way. Not too difficult with a 135-lbs machine.
 
Does anyone use a 3 position reserve type tap? The positions are On, Off, Reserve.
These have a standpipe perhaps 2 or 2&1/2" long and bring fuel in from the top when in the "on" position. In the " Reserve" position fuel flows in around the base of the standpipe.
This way you have a decent reserve amount but also get full range from the tank.
I used one of these on the Special, Pingel brand as high flow was needed. 30 miles on reserve but it's a fairly big tank, 19 litres.

Glen
 
Last edited:
Does anyone use a 3 position reserve type tap? The positions are On, Off, Reserve.
These have a standpipe perhaps 2 or 2&1/2" long and bring fuel in from the top when in the "on" position. In the " Reserve" position fuel flows in around the base of the standpipe.
This way you have a decent reserve amount but also get full range from the tank.
I used one of these on the Special, Pingel brand as high flow was needed. 30 miles on reserve but it's a fairly big tank, 19 litres.

Glen

I use one on a B44 Victor Special tank, works well and the tank is nearly flat at the back so the one tap gets to nearly all the fuel. Using Two with a tank that traps fuel on one side would work.
 
Status
Not open for further replies.
Back
Top