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hpn gas tank vs markus underseat
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Mon Feb 06 2012, 03:57am
a/k/a Jake

Registered Member #15
Joined: Sat Jan 17 2009, 04:28pm

Posts: 232

I took a couple more pictures of the tank and crossover tube. The side legs do drop down a good bit below the main part of the tank:
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Here's the crossover line:

Flipping the tank upside down, you see it connects between the middle part of the tank and the legs. It doesn't connect to the return line, so there's nothing but gravity transferring fuel out of the legs.

A few months back I ran the bike until it was out of gas and then drained and measured all the gas that remained. It was 4.5 kg or about 5.5 L of gas. I did it again today with water and measured the amount left only in the legs when the main part of the tank is totally drained: 2.9 kg = 2.9 L. The amount my pump system would scavenge is in between.
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Sun Feb 12 2012, 12:10pm
Registered Member #115
Joined: Tue May 19 2009, 10:35am

Posts: 168
My apologies, I got the HPN setup confused with the Markus tank (I have both).
You are indeed correct about the HPN lines.
The Markus tank hooks up to the RETURN line.
You add a t-piece and cut the lines.

I've JUST got my bike back from my last trip: I ran out of time to ride back so I left it then air freighted it back.
I will confirm this, but looking at my tank both in and out of the bike, I THINK that the various drains are all arranged to allow the legs to drain by gravity into the main tank.

It's tricky to confirm for sure since (I don't think) the tank sits like your photo shows it when it's installed. It's tilted more.
You took a photo of it installed, but to me it's not clear enough to really see the angle.
And my tank isn't back in the bike after rinsing and flushing it so I cannot confirm.

Incidentally, why don't you just call up Klaus at HPN?? He's a friendly guy and I've talked to him a few time by phone, plus met him face to face. You need to speak to him tho, unless your German is good. Can try an email too.
Cut to the chase and ask him!! Use Skype to call if the thought of an overseas call is daunting. And remember the time difference.

As far as my HPN tank draining both legs, to my best knowledge it does NOW. But I also had problems. Either a kinked hose, or perhaps vapour block. I dropped by HPN and Klaus helped me solve the issue. Since we changed three things at once is hard to know which solved my issues:
- replaced fuel line with a different hose (different rubber)
- adjusted length so a better routing
- added an outer/insulating cover to it (it gets hot there and might be vaporizing the fuel)

But I'll take careful note when I put mine back in and see where the drains are: who knows maybe I still have a draining issue. You seem to have been pretty methodical about checking.

You might try putting the tank in the bike and then having it sit level: even someone sitting on it.
Then making a mark on the tank that is level to the ground.
Then removing the tank and setting it at that level and seeing if it DOES drain.
Even putting some fuel in and open the stopcocks and see if it DOES all drain when it's out of the bike, at the actual angle.

I might do this myself.

Seems a shame to add a pump just for that. I think you should consider a change in hose routing before you do that: simple is better!!! I have an extra pump because of the Markus tank and it's an extra hassle.

Anyways perhaps I'll call Klaus for a chat myself and say I'm back from my trip and the bike went well. And i'll ask him about the draining.

Alan Jarvis

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Sun Jun 11 2017, 12:22am
Registered Member #59
Joined: Sat Jan 24 2009, 06:09am

Posts: 50
Saddlemen seats made an HP2 seat with a hole in it for the Markus tank. Worked out very nicely. I have the HPN and I'm thinking of adding the Markus tank for the extra long range,
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Sun Jun 11 2017, 03:24pm
Registered Member #648
Joined: Tue Mar 19 2013, 02:20pm

Posts: 54
It was my seat.

For anyone thinking/interested in doing something similar...

I had to supply the seat to Saddlemen with the hole already cut. An important customisation I specified was to 'scallop' the section of the seat near the hole. I cut the smallest possible hole size but it proved very hard to get a good grip on the cap. The options were either to cut a bigger hole or to lower the foam height by scalloping.

Nearly 3 years later, I'm still very happy with my modified seat.

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Mon Jun 12 2017, 02:07am
Registered Member #59
Joined: Sat Jan 24 2009, 06:09am

Posts: 50
This is the seat Saddlemen made for my HP2. It's much so much better than the stock seat

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