Anyone tried increasing fuel capacity on a Vmax?

Lakehouse2021

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I really enjoyed running my 600 vmax last winter, but I'm taking a bunch of harassment from my buddy for running out of fuel on runs. Their new sleds can go alot farther between gas stations then mine can. Has me wondering if there might be a way to add additional inline fuel capacity? Anyone tried this?
 

super1c

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If I remember right this is a 96? Man the were pigs on fuel. The best I got was only about 8-10 mpg downhill if I remember. There are a few things we did back then that did help. Removed layer from head gasket or change to 95 head gasket. Jet down (can’t remember to what) and change to a good set of carbon fiber reeds. improves mpg and peps it up nicely. Do a search and see what ya find. I’ll see if I can find the info in my old notes.
 

Lakehouse2021

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If I remember right this is a 96? Man the were pigs on fuel. The best I got was only about 8-10 mpg downhill if I remember. There are a few things we did back then that did help. Removed layer from head gasket or change to 95 head gasket. Jet down (can’t remember to what) and change to a good set of carbon fiber reeds. improves mpg and peps it up nicely. Do a search and see what ya find. I’ll see if I can find the info in my old notes.
Thanks super1c, it is a 95 sled, still looks good too.

carbon reeds makes sense, I'll look into that.

I was thinking of raising the seat up off the tunnel 6 inches and placing a marine tank under and build the lines as inline with a pump to move fuel with touch of a button... Am I crazy?
 

Maim

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do not need a pump. the tour buddy for the yamaha's of that era, mounted on top of the belt gaurd if memory serves. they would hook the vent line to the straw in the tour buddy and it would vent through the tour buddy vent. it will suck the tour buddy dry 1st before using any gas out of the main tank. brother made a 5 gallon seat spacer/fuel tank/tunnel extension for my old sx500r that i sold him when i bought my rx war. he was then able to go just as far as the rx for range when we rode together with it geared down for a 136" track. the old belt gaurd one only held 2 gallons but that was usually enough with that sled in stock form to match the rx war and my other brothers sx viper for fuel range.
 

Lakehouse2021

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do not need a pump. the tour buddy for the yamaha's of that era, mounted on top of the belt gaurd if memory serves. they would hook the vent line to the straw in the tour buddy and it would vent through the tour buddy vent. it will suck the tour buddy dry 1st before using any gas out of the main tank. brother made a 5 gallon seat spacer/fuel tank/tunnel extension for my old sx500r that i sold him when i bought my rx war. he was then able to go just as far as the rx for range when we rode together with it geared down for a 136" track. the old belt gaurd one only held 2 gallons but that was usually enough with that sled in stock form to match the rx war and my other brothers sx viper for fuel range.
Love the idea of this, unfortunately they are out of business... Another company out of Oregon is making larger tanks but only replacements, not secondary. Tour Buddy, spoke with one of them today, really nice guy, but tooling up for me would be a REALLY high cost of creation...

I'll continue my ideas...
 

Maim

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you could get an aluminum one built for on the belt gaurd as it is not much heavier than a plastic one would have been.
 

Maim

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just had evil thought. small engine fuel tank for a snow blower or water pump as those can be gotten at a store like fleet and farm and hold over a gallon of fuel. had to put one on a mini z when the oe tank failed.
 

Lakehouse2021

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just had evil thought. small engine fuel tank for a snow blower or water pump as those can be gotten at a store like fleet and farm and hold over a gallon of fuel. had to put one on a mini z when the oe tank failed.
I'm thinking along those same lines, I was searching for a small off-shelf tank from something. I need to take some measurements and find one that fits.

The aluminum one is also an option, I could tig one up but it takes a lot of work to get them air tight...
 

Maim

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I'm thinking along those same lines, I was searching for a small off-shelf tank from something. I need to take some measurements and find one that fits.

The aluminum one is also an option, I could tig one up but it takes a lot of work to get them air tight...
i know sealing the pinholes is a pita but might be an epoxy sealer gas safe you could line the tank with. i know they make one for re conditioning old motorcycle tanks that are full of rust.
 

Jack99

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Is the 95/96 factory gearing too low - which creates too high of engine RPM (which loves fuel)?

If wondering, I always felt my '99 Venture 600 2-UP was geared too low (which creates high RPM engine) and I changed its chain's upper gear. Went 2 teeth higher (on upper gear) and its engine RPM is now a little lower (for its same ground speed). Since I do 99% packed trail riding, knocking its engine RPM lower worked great (for me).

Perhaps gear changing might work great for your 2-stroke engine as well?
 
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Lakehouse2021

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Is the 95/96 factory gearing too low - which creates too high of engine RPM (which loves fuel)?

If wondering, I always felt my '99 Venture 600 2-UP was geared too low (which creates high RPM engine) and I changed its chain's upper gear. Went 2 teeth higher (on upper gear) and its engine RPM is now a little lower (for its same ground speed). Since I do 99% packed trail riding, knocking its engine RPM lower worked great (for me).

Perhaps gear changing might work great for your 2-stroke engine as well?
Jack, great ideas, thanks! I went the other route and just bought a 4s... LOL now Im working on gettting it ready for snow
 

Maim

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nice lol. the nitro in your sig could use gearing up as well as they where geared for snowcross corner to corner snap but still way better fuel milage than a twin. it should still get north of 15 mpg in stock form.
 

Lakehouse2021

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nice lol. the nitro in your sig could use gearing up as well as they where geared for snowcross corner to corner snap but still way better fuel milage than a twin. it should still get north of 15 mpg in stock form.
I am SO excited to get greater than 8mph!!! and have a few extra ponies to work with on the trail...
 

Lakehouse2021

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Not sure about a 95, but with proper jetting, my sx 600 with tempaflow will get 11 or maybe even 12 mpg.
Thanks Norwegian! I tried going up and down the jetting charts last winter, I couldn't get any better than 8... I know there are other things I could do to improve performance, but I took the lazy way out and bought a 4s. :)
 

BornYamaha

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If it has many mile on it replace the needle jets. They are brass and wear over time from the vibration and enlarge. Will never get great mpg but it may help. Especially if it sounds garbly in the mid range
 

Lakehouse2021

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If it has many mile on it replace the needle jets. They are brass and wear over time from the vibration and enlarge. Will never get great mpg but it may help. Especially if it sounds garbly in the mid range
Thanks Born, Last winter I tore the engine down to crank halves and changed both seals, then proceeded to rebuild everything all the way upto carbs. I changed jets several times and finally got it running less-rich but it might still be able to lean out further. But I dont think that would get me another 30 miles of trail, especially the way I drive this thing... LOL
 


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