Acerbis/HPN tank question

[brassmonkey001]

I have the 43l tank on my bike and when the fuel level gets low it starts to cut out as you'd imagine it would.
However, I put it on reserve and then check the fuel level when I get home with a torch and I see that the level is actually above the top of the petcock. So I've always assumed that it's an idiosyncrasy of the bike that it gets a bit of fuel starvation when the level starts getting low due to the lobes of the tank being very low, combined with the fact that I have both inline fuel filters and quick-release connectors making the flow of fuel not quite as efficient as it would be if the fuel lines were straight through to the carbs.
I happened to notice last night that the nearside petcock was totally submerged in fuel but the offside one was sticking out above the fuel level, so I wondered if this was intentional, like a sort of dual reserve system? I.e. you go to 1st reserve when fuel is getting low and 2nd reserve is when you really ought to make finding a petrol station a priority. Not an issue on British roads I know, but maybe useful when out in the desert perhaps?

And no, I didn't have the bike on the sidestand...

 

[Sean Kelly]

Hi

I always use mine like that, something like 40 miles on the first reserve and somewhat less on the second. Could never get fuel filters working right with the big tank.

Sean

 

[Flipfly]

Al, i think it is a trait of the HPN tank.

Mine runs out and then does hardly any miles on the reserve on the left of the tank. It then does around 60 miles on the other side.

It is a pain, but they do not seem to be equal in the way they pick up the fuel on reserve.

I use the left side first and the right as a last resort.

need to remove the taps really to find out why this happens, but realistically it's easier to just fill it back up with fuel

 

[brassmonkey001]

Answered my own question

After trying it this morning with the N/S tap on 'On' and the O/S tap on 'Reserve' I have reached the conclusion that it is not something that has been engineered in on purpose. Rather, it is more likely the designers thought 'Ah, they're near enough level' and left it at that.
I have in the past tried running one lobe then the other but with the set-up I've got it never seems to work properly - the float bowls can't fill up fast enough at speed without fuel flowing from both taps.

At least I know now that when it hits reserve I should turn the O/S tap first.

Phil - have you got your left and right mixed up? The left (Nearside) should hold much more fuel than the right (Offside).