Petrol reserve tap

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Aug 13, 2008
Ran out of fuel the other day so I switched on the reserve tap and only got 5 miles before it spluttered to a halt.I had to lean the bike right over to the left to try and get the remaining petrol in the right hand side, to the reserve tap.Then got just 2 miles.Anyone else had this problem.How much is in reserve?
1976 mk3 850 e/s.
I have a Roadster tank on at the moment, and last year when mine went onto reserve, I got about 12 miles before having to resort to tipping the bike over to get the dregs across to the reserve side, and then got about 4 miles where I knew that there was a petrol station, but not confident if it would be open. Luckily for me it was :D

Possibly a taller stand pipe on the resrve tap would help matters :?:

The above event causes me to head :p straight to the nearest petrol station when the fuel goes onto reseve, and so far always with success.
Possibly a taller stand pipe on the resrve tap would help matters

The stand pipe is on the main tap not the reserve.

Commando 1954,
Are you sure you have the taps in "correctly"? I put the quotes on the word as not all dealers seem to have put the reserve tap on the left side.

Another possibility is you have two reserve taps or two main taps. The frame recess will hold enough fuel on one side to run about 5 miles when the main goes dry if the same tap is in both sides.
My '72 fiberglass tank that I've had since new has the Reserve decal and tap on the right but the used steel tank I just got has it on the left. Maybe it depends on country regs. or conventions. My '72 came from Comerfords in England.

I also noticed the steel tank flip cap faces the opposite way so you can't see in very well when riding. My guess is that this is a safety reg in case of a crash where the cap flips up while you are sliding forward on the tank - Owwwww!

Up to 1974, the Commando main tap was normally on the left, and the reserve on the right, with a "Reserve" sticker applied to the right side of the tank close to the tap.

For 1975 (MkIII) the taps swapped sides. The reserve now on the left, and main on the right (this can be checked by consulting the various year models of riders' handbooks).
The new '75 taps themselves had a quadrant-shaped plate that matched the arc of the lever's movement, with either "Main" or "Res" stamped on them, and the reserve tap lever now had to be turned up for ON instead of down.
This change may have had something to do with (impending?) US legislation, as the L/H gearchange and labelling/labeling of switches etc. were?

Previous owners could of course have swapped them over, or trimmed the standpipe? or fitted two reserve taps? As I doubt there are many original taps still working?
The best thing to do is to remove them both and check what is fitted and where?
My '73 basketcase came with a fiberglass tank with the fuel cap hinged at the front. I don't know which side the reserve tap was on, as it was in a separate box. The reserve is now on the right, as I was told is correct for the '73.
The steel tank (which is on the bike now) has the fuel cap hinged at the rear. I have yet to see a newer bike with the fuel cap hinged at the front, so I would assume this is either by regulation or convention.

As to only getting about 7 miles on reserve, there are several factors to consider:

1. What is the volume in each side of the tank? If the tank has been repaired or 'sealed', interior volume is reduced.

2. How far over to the main side had the bike been leaning before running the main tap dry? One could potentially slosh all of the fuel over to the main side, leaving the reserve side essentially dry and the only reserve in the tank being the little bit below the standpipe.

3. How high is the standpipe on the main tap? My apparently original main tap looks identical to the reserve tap, save for the approximately 1 1/2" long tube (standpipe) inside the brass mesh. This standpipe prevents the bottom inch-and-a-half of fuel from going through the main tap.

4. Do you have two main taps or two reserve taps? Either of these conditions will greatly reduce your reserve capacity, as two reserves with a reserve tap in the main position will drain that side of the tank completely, and two mains with a main tap in the reserve position will prevent you from accessing all the fuel in the tank.

While out on my ride on Saturday (still sorting out and breaking in), I stalled the bike at a traffic light. Tried to kick start it and failed. Rolled over to the side of the road, put it on its sidestand, and took off my jacket. Tried to start it again and it fired right up. Rode about four miles, and it happened again! This time, I rolled it over to the side of the road, under a tree, and noticed that the fuel line was dry. I hadn't paid attention to the fact that I had gone over 130 miles. I leaned the bike over to the right (my reserve side), opened the reserve tap, and started right up. Rode about 12 miles to my local gas station, and put 3.07 gallons in the tank.

I still need to get used to the fact that there isn't a low fuel warning light on this thing.

Since there was at least a quart of fuel left in the tank, I think the Pakistani tank holds about 3 1/2 US gallons
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