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Looking at longer rides where 2.5 won't reach to the next gas station. I've got the stock tank on my 2004 and don't want to switch out with an Acerbis 3.2 because I want to be able to keep the bike light for shorter rides, so I'm looking at external options like the rotopax, maybe a 2 gallon-er? Are the 2 gallons too big, or are there other options I don't know about? Thanks in advance.   

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You're going to have the same amount of weight anyways. Why not run a 3.7,3.9 or 4 gal tank then switch back to the stock tank for the shorter rides? That way there's no rigging,lugging and pouring from an aux can all the time.

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The roto-pax is actually a 1.75 us gal. Unless you get the smaller 1.0 gal.

I didn't like weight up high with the 1.75 sitting behind the seat.

Love my Acerbis 3.7 so much better, as far as handling the steep rocky hills.

And I've gott'n over 240 miles with my stock engine and the 3.7

Edited by bucket list
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Plastic tanks are lighter than stock steel tank and they can carry 2 gallons as well as 3.7, 3.9, 3.2 or whatever full is for your particular make.  

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13 hours ago, bumtarder said:

You're going to have the same amount of weight anyways. Why not run a 3.7,3.9 or 4 gal tank then switch back to the stock tank for the shorter rides? That way there's no rigging,lugging and pouring from an aux can all the time.

I was initially looking for a one-size fits all solution, which I think ultimately the acerbis tanks are, with the exception of IMO the stock tank just looks cool, ha. But I think the reality is I won't be doing longer trips like this every week so getting the acerbis and *putting less gas in the tank when I don't need it is the obvious best way to go. @olendorf 

Edited by J.M.

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8 hours ago, bucket list said:

The roto-pax is actually a 1.75 us gal. Unless you get the smaller 1.0 gal.

I didn't like weight up high with the 1.75 sitting behind the seat.

Love my Acerbis 3.7 so much better, as far as handling the steep rocky hills.

And I've gott'n over 240 miles with my stock engine and the 3.7

Weight was another consideration, good to hear your experience with having it strapped and sloshing on the bike rack wasn't ideal. Thanks for the range on that too, that would clear big sections easily and I wouldn't be stressing about the next fill-up. 

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I use the 3.9 Clarke and love it.  For my "lunatic" Tuesday rides with my KTM friends (yes some of them are okay guys...ha) on the really gnarly stuff,  I made a dipstick for the tank, and allow 4L per 100Km we intend to ride.  I just dip the tank and figure out how much to add.  This means that I have the lighter plastic tank on at all times, and simply decide how much fuel weight to start the day with depending on the ride.  For those much longer DS rides I just filler up.

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18 minutes ago, dad2u said:

I use the 3.9 Clarke and love it.  For my "lunatic" Tuesday rides with my KTM friends (yes some of them are okay guys...ha) on the really gnarly stuff,  I made a dipstick for the tank, and allow 4L per 100Km we intend to ride.  I just dip the tank and figure out how much to add.  This means that I have the lighter plastic tank on at all times, and simply decide how much fuel weight to start the day with depending on the ride.  For those much longer DS rides I just filler up.

Are there any big differences between Clarke and Acerbis tanks?

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Not sure.  From the image the Acerbis looks perhaps a bit wider, and my Clarke has a bit more height at the gas cap, but hard to tell. 

The dipstick idea is still a champ: Fill the tank right full, find a length of aluminum stock 1/2 inch wide by 1/8 or so, and gently insert it down til it gets to the petcock side, bottom of the tank.  Now pull it out and use an impact engraver to mark a line to show when the dipstick is fully inserted.  Now....unhook the fuel line off the petcock and direct it into an empty gas can.  Turn on the fuel and measure exactly 1 Liter out, then dip the tank and mark the new level on the dipstick.  Drain another liter out, mark again.  Continue until you hit reserve (fuel stops flowing in the normal petcock setting).  At this point you can mark the lines on the new dipstick with the number of litres above reserve.  (0 at the reserve line, and 1,2,3 as the lines go up the stick.)  (yes with a vacuum petcock you will need to apply vacuum for this process.....)

 Now select reserve and carefully measure the fuel that comes out, draining til empty, so that you know the total reserve volume.  Finally, put the cap back on to the "now dry" tank, lay the bike down on its left side to get the fuel trapped in the right lobe to flow across to the left lobe, stand it up, and again measure the total volume of new fuel that flows out.  You should end up with a solid knowledge of the useable fuel before reserve (and a dipstick that you can use to guide your daily fuel load decision), a solid idea of the reserve fuel capacity, and a solid idea of the additional "trapped" fuel reserve in the right lobe. 

In my case, after modding my petcock reserve standpipe (I installed a Raptor manual petcock with virtually no reserve, see other articles by me on this) I ended up with:   Reserve 1.5L.  Main tank plus reserve: 14.7 (Clarke 3.9US gal= 14.7 so they did not lie!!)   AND....an extra 1.7L that is trapped on the right side as the fuel level drops.  So when I hit reserve I actually have 1.5+1.7= 3.2Litres, at 4.5L/100km this gives me 70km!!

The value of this work is to aid you in deciding how much fuel to have onboard before setting off on that gnarly, but short distance ride.  So, if it is a 120km day, I need about 6L.  So I dip the tank to see how much is in it, and add whatever it takes to get to 6.  Now I know that this is on top of the 1.5+1.7 that is in the tank when I hit reserve, so even if I badly misjudge the length of the day, I have quite a margin of safety.  Alternatively, if I really want to go light, I can factor the 1.5+1.7 into my fuel needs for the day....

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8 minutes ago, J.M. said:

And answered my question in this post 🙂

 

They don't review the Clarke 3.9 so here goes: from these new images the outer shape and size is very similar.  In my case it mounted easily, and clears the rad guards.  The petcock and rad shroud mounting holes are all threaded and ready for the stock bolts...and are brass lined.  I overpressurized my tank (hot day, slow hard ride so extreme heat, with resulting high fuel vapour pressure build up in tank:  and as previously discussed in another thread, tanks vent in only, not out) and the tank itself had no issues....finally got a fuel leak going at the petcock seal...which ceased as soon as I opened the cap to see what was going on and had the huge whoosh of fuel vapour blow out). 

As I mentioned earlier, tank holds 14.7L (3.9 US Gal) plus 1.7L that is trapped on the right side and can be used by laying bike over on left side after exhausting the reserve fuel.  

What was not mentioned earlier: no matter what tank you pick you will find some intellectually interesting challenges in routing the fuel line from whatever petcock you use, to the carb.  In the case of the Clarke 3.9 with a Raptor petcock the outlet nipple on the petcock lines up perfectly with the carb intake nipple on the carb (stock S) and thus it was the simplest possible connection: a straight hose 4 inches long.  If you search this forum you will find lots of challenges and ideas used to connect petcocks to carbs in the various configurations that exist.

 

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5 hours ago, J.M. said:

But I think the reality is I won't be doing longer trips like this every week so getting the acerbis and swapping out the stock when im not on the long-haul is the obvious best way to go. 

No. The obvious way to go is to put less gas in your tank when you don't need it.   It reminds me of an Amazon review where the lady got a 2liter camelback and returned it for a 1 liter size because 2liters of water was too heavy.

 

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16 hours ago, bucket list said:

And I've gott'n over 240 miles with my stock engine and the 3.7

Wow! That is 64+ mpg.  Downhill both ways? 🤪  That rocks! I can barely hit 40 mpg 2002E.

I'm not a big fan of the large bulging tanks either.  When needed, I put a 2L bottle in my tailbag to ensure I can get back without walking.

image.thumb.png.8e51b96eb94606a2a367d1621a9331e1.png

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The Clarke 3.9 looks great...it is not an obviously larger tank unless you really look at it....and it does not seem to inhibit flying either.

(I did not crash, but needed help to get back out of the trees!)

IMG_5563.jpg

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2 hours ago, Ruggage said:

Wow! That is 64+ mpg.  Downhill both ways? 🤪  That rocks! I can barely hit 40 mpg 2002E.

I'm not a big fan of the large bulging tanks either.  When needed, I put a 2L bottle in my tailbag to ensure I can get back without walking.

image.thumb.png.8e51b96eb94606a2a367d1621a9331e1.png

Ya, i resisted going to the larger tank, like the slim feel of the stock tank, but i've been pleasantly suprised  that the extra width doesn't bother me and my tank bag sits on it better.

That mileage is from a mix of riding, mostly FSR's, some hiway and a little stop and go city. Those pumper carb's on the E contribute big time to the lower fuel mileage and since i'm mostly adventure riding into very remote places, that little CV carb on my new S model does me just fine. Heck, i haven't even gott'n around to doing the 3X3 and jetting yet and with the awesome mileage i'm getting, may never do it.

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10 hours ago, dad2u said:

Not sure.  From the image the Acerbis looks perhaps a bit wider, and my Clarke has a bit more height at the gas cap, but hard to tell. 

The dipstick idea is still a champ: Fill the tank right full, find a length of aluminum stock 1/2 inch wide by 1/8 or so, and gently insert it down til it gets to the petcock side, bottom of the tank.  Now pull it out and use an impact engraver to mark a line to show when the dipstick is fully inserted.  Now....unhook the fuel line off the petcock and direct it into an empty gas can.  Turn on the fuel and measure exactly 1 Liter out, then dip the tank and mark the new level on the dipstick.  Drain another liter out, mark again.  Continue until you hit reserve (fuel stops flowing in the normal petcock setting).  At this point you can mark the lines on the new dipstick with the number of litres above reserve.  (0 at the reserve line, and 1,2,3 as the lines go up the stick.)  (yes with a vacuum petcock you will need to apply vacuum for this process.....)

 Now select reserve and carefully measure the fuel that comes out, draining til empty, so that you know the total reserve volume.  Finally, put the cap back on to the "now dry" tank, lay the bike down on its left side to get the fuel trapped in the right lobe to flow across to the left lobe, stand it up, and again measure the total volume of new fuel that flows out.  You should end up with a solid knowledge of the useable fuel before reserve (and a dipstick that you can use to guide your daily fuel load decision), a solid idea of the reserve fuel capacity, and a solid idea of the additional "trapped" fuel reserve in the right lobe. 

In my case, after modding my petcock reserve standpipe (I installed a Raptor manual petcock with virtually no reserve, see other articles by me on this) I ended up with:   Reserve 1.5L.  Main tank plus reserve: 14.7 (Clarke 3.9US gal= 14.7 so they did not lie!!)   AND....an extra 1.7L that is trapped on the right side as the fuel level drops.  So when I hit reserve I actually have 1.5+1.7= 3.2Litres, at 4.5L/100km this gives me 70km!!

The value of this work is to aid you in deciding how much fuel to have onboard before setting off on that gnarly, but short distance ride.  So, if it is a 120km day, I need about 6L.  So I dip the tank to see how much is in it, and add whatever it takes to get to 6.  Now I know that this is on top of the 1.5+1.7 that is in the tank when I hit reserve, so even if I badly misjudge the length of the day, I have quite a margin of safety.  Alternatively, if I really want to go light, I can factor the 1.5+1.7 into my fuel needs for the day....

No need for a dipstick, holds 16 L, measured. Clarke tank and I'd replace with same if necessary:

DSC02869.JPG

Edited by shuswap1
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1 hour ago, bucket list said:

Heck, i haven't even gott'n around to doing the 3X3 and jetting yet and with the awesome mileage i'm getting, may never do it.

I see the merit to keep as is without the mods for the mileage. Trade off is missing the AP squirt of power (ooh-rah!).

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