SAFETY CONCERN ?? 2017 G4-850 Fuel tank pressurized

Not the usual fit and finish you would expect from ski-doo. All jokes aside it collects a lot of pine needles/tree branches keeps pushing tank up. Always garaged & trailered in enclosed trailer. Maybe skidoo will perform another bandaid fix haha.
wow that sucks! I wonder if this is a result of the tank being pressurized and then warping from it over time?? On the bright side you shouldn't have any trouble getting it warrantied.
I will have to take a closer look at mine!
 

NHRoadking

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I was really hoping BRP would chime in. And not with a bs bracket or something like that.
Did you email them or reach out to them on they Facebook page? They've always answered my emailed questions and on their Facebook page.
 
why not eliminate the valve . i cut mine to away have zero pressure in the thank . i just cut the little rober valve so air can come in out . i did that because the gas pump and gas pressure regulator is in the tank . if air pressure increase buy one psi , gas pressure raise buy one psi also . not sure if it holding 1-2-3 psi or vacuum ?? psi but i know it have a big effect on gas pressure and engine performance variation .
i did play with gas pressure regulator and a wide-band to tune ported engine .
 

Clutched Films

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why not eliminate the valve . i cut mine to away have zero pressure in the thank . i just cut the little rober valve so air can come in out . i did that because the gas pump and gas pressure regulator is in the tank . if air pressure increase buy one psi , gas pressure raise buy one psi also . not sure if it holding 1-2-3 psi or vacuum ?? psi but i know it have a big effect on gas pressure and engine performance variation .
i did play with gas pressure regulator and a wide-band to tune ported engine .
Wouldn't the air vent be designed to allow more than enough air through while running at WOT? Pressure in the tank wouldn't affect HP + or - unless the vent is plugged. pressure from the injectors is what it is you can't turne up you injector pressure with Tank pressure unless you get a computer programmer. I thought the 800R injectors where pretty much maxed out. Maybe the 850 injectors aren't ? I think the vent works fine while running just sucks at venting while on the trailer up to the mountain or sitting on the hill during the day. That's how I thought it worked could be wrong I'm just a hydro physicist. Currently working on converting this beer into pure p*ss:beer; has the cut on vent rubber helped? Does BRP make a vented cap for the 850 like on the race sleds? I have been leaving the cap loos on my 850 to keep the tank from bulging up so far it kinda helps.
 

medicman

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This pressurized gas tank is nothing new with ski doo. I had a 2005 rev 800 and did the same thing. Point down hill gas runs out tube. Ride a bit and stop on a level surface and releas the gas cap and massive back pressure. Ski doo used a ****ty vent/ valve system. Pulled the valves out and re routed the vent lines. No more problems. This continued clear up through the last 2010 ski doo I had
 

Matte Murder

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Long term issue with Doo. I would bet that’s why there some extra room in the XM tanks that most people would burp and put another 1/2-3/4 gal in the tank. A little room for expansion. It actually annoying as heck sometimes. I had to slip off a small cliff a couple weeks ago and the sled got stuck nose down. Took us about 15-20 min to get it out and the whole time gas is peeing out the vent. It seems to be siphoning once it starts to flow too. You learn on the warm days to not park downhill but if you get stuck downhill you are fooked. I also had a sled drip gas on my floor of my trailer over the summer and eat a hole thru the rhino liner about a foot across from this same vent and pressure problem.
 

Ox

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This pressurized gas tank is nothing new with ski doo. I had a 2005 rev 800 and did the same thing. Point down hill gas runs out tube. Ride a bit and stop on a level surface and releas the gas cap and massive back pressure. Ski doo used a ****ty vent/ valve system. Pulled the valves out and re routed the vent lines. No more problems. This continued clear up through the last 2010 ski doo I had
Apparently they don't have a vent hose down to one footwell, then back up to the bars, and back down to the other footwell anymore?

Any reason not to - doo to fuel infection - or other?


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Ox

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OK, well I had'ta figger it out fer muh'self....

I want to set my sled up with an aux gas tank like I have been running for the last 25 yrs. It's more work and investment up front, but a lot more better when it's time to ride.

I figger on making an alum tank that will set just behind and a bit above the OEM tank, and then I plumb them right into the vent line on the main tank, and let it suck it dry.

The very nice points of this are that you can fill it clear up if you want for a big ride, or even an overnight ride. (planned or not eh?) If you don't want any, don't put gas in it. I think my old tank on my ZX weighs 12# @ 10 gallon capacity. But the aux tank empty's first as it continuously refills the main tank as you ride, where that five'r on the back is still there....

Of course the part about not having to try to pour gas in the weather, or possibly getting snow in your tank, or ....
I just find it so much better to toss 3-4 gal in the back and suck it dry right away, and not frett over gas - even on the [planned] short rides.

Years ago me and my chum sucked down 20 gallons breaking trail (and subsequently camped out overnight) on our old 600 / 136's. (1990's) I will say tho that I don't think that we have ever used more than 15 gallons since we got out 800/151's or longer. But I have hopes of some big rides in the future yet, so ....

EH _ KNEE _ HOW .....

So I pulled the plastic back and found the vent line. Just setting in the garage - the tank was still under pressure when I took the cap loose. (good grief...)


So here you can see where the fitting fit into the tank neck, just below the cap:





You jist need to back out the T15 screw (that you can't git to) and the fitting pulls out. It has an O-ring seal on the outside:




Inside you find just a piece of rubber that is acting as a check valve. I'm sure that if you wanted to "fix the problem" all you'd haf'ta doo is grab ahold of it with a needle nose or whatnot and pull on it to break it, and then put the fitting back on. I'm not sure if I'll just "fix" this fitting, or make a new one for my porpoise?



I have heard of a cpl of tanks imploding before as well, and I would venture to guess that the other end of the vent line - which comes out above the left shock got iced up / plugged, and the fuel pump had more suck than the plastic tank had structural integrity. Traditionally these vent lines use'ta go down to one foot well, double back up over the top and back down and vent out above the other foot well. It may not be 100% drip proof, but by going all that way - I don't know that I've ever seen one drain out - no matter how long a sled was upside down, so ....


I would not recommend just clipping the rubber seal / check valve and letting the vent line go strait out to the ski recess in the pan like OEM. I am sure that you would end up with a lot of drainage, so if you go this route, I would highly recommend that you go with the old skewl looped vent line like I just mentioned above. It worked fine for decades prior...

FWIW - mine is an '18.


Also outlined a bit in post 50 above.



BTW - The vent fitting takes 1/4" ID line in case anyone wants to make the change.

I'd be willin' to bet that the porpoise that they went with this design is for EPA mandates regarding gas tank evap.
Same as that "Service Engine Soon" light that comes on if you don't git'cher gas cap on your truck tight enough.
Sure glad someone is lookin' out for my well being!



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