Awful gas mileage.

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02YamiSxViper

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Location
Ottawa
What would cause a stock viper to have ridiculous gas mileage. Went 110km (75 miles) on one tank.


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What color are your plugs? Do you have any bad bearings in drivetrain or wheels? Is your parking brake on lol. Actually I'm serious about the parking brake…… you wouldn't be the first.
 
How much actual fuel did you use? When mine says empty it has a few gallons left. Worst I've gotten this year is 9.5 MPG (USA gallons), when it was above freezing.
 
I got 7-8 MPG on an unpiped viper. My bearings are brand new replaced them 200mi ago. The whole skid was rebuilt. I just went through the carbs again. I guess the person who owned this before me messed with the fuel screws. Had a washer under the o-ring in one spot, the other 2 were good, not sure if that would do anything or not. Checked and cleaned everything else. As for the parking break, no it wasn't on but I've definitely done that before. Pretty sure I accidentally turned it on when reaming on the handle bars trying to get unstuck one time. This was on hard pack BTW, my wifes SRX went through only a quarter tank while my stupid gas light was on. My fuel screws are set at 1 7/8 ish and my needles are 3.25 as per Dons advice.
 
Well the typical things I see posted are 1) check your track tension 2) Clean your clutches/belt 3) check your ski alignment, should be slightly toe'd-out 4) try driving slower just to see if that makes a difference (you should get 11-12 easily if you stay under half throttle on hardpack).
 
Track tension is good, perhaps a little on the loose side, skiis are toed out 1/8". My clutches are spotless, cleaned everything in the summer. When we went my wife stayed on my tail the whole time, and she used like 1/2 or more less fuel than me. I think something else is happening.


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No, I checked that. With the lever flipped up the choke is completely off.


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02YamiSxViper said:
I got 7-8 MPG on an unpiped viper...
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I can echo the above 11-12 mpg range when riding on groomed trails with a stock Viper, at all around speeds, some cruising and a bit of hot rodding. May even see 13mpg range from time to time. That's not estimating, it's set the tripometer on a full tank to add up the miles and divide by how many gallons are used up thru the last fillup.

02YamiSxViper said:
... I guess the person who owned this before me messed with the fuel screws. Had a washer under the o-ring in one spot, the other 2 were good, not sure if that would do anything or not...
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Fuel screws should have a washer. The order is: Fuel Screw > Spring > Tiny Washer > Tiny O-ring
I've found a few carbs that are missing this washer, and it's very easy to pull the screw and spring out and forget that there are two other little parts still inside the carb! It also doesn't sound like a good idea to let that spring bear up against the o-ring, as the end of the spring could conceivably damage/deform the flexible o-ring.
If the tiny o-ring is in good condition, it will hold all four parts together nicely for installation into the carb, as the ID of the o-ring grips the shank of the fuel screw.
 
srx700c said:
Fuel screws should have a washer. The order is: Fuel Screw > Spring > Tiny Washer > Tiny O-ring
I've found a few carbs that are missing this washer, and it's very easy to pull the screw and spring out and forget that there are two other little parts still inside the carb! It also doesn't sound like a good idea to let that spring bear up against the o-ring, as the end of the spring could conceivably damage/deform the flexible o-ring.
If the tiny o-ring is in good condition, it will hold all four parts together nicely for installation into the carb, as the ID of the o-ring grips the shank of the fuel screw.
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Yea I know the guy before me messed up on one. But I wasn't sure if having the washer under the O-ring would cause me to burn too much fuel. The rest of the screws were Screw-Spring-Washer and Oring but one had the washer under the o-ring so on that one screw it was Screw-Spring-Oring and washer. Other than that the carbs looked good, the pilot and main could have been screwed in a little tighter but I don't think thats cause for concern.
 
Maybe throw the back of the sled up un the air, pull the belt, and see how everything spins. Should spin track by hand quite easily. There has to be excess drag somewhere.

That's if jetting looks good and clutches / rpm are where they should be.
 
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ssrrxx said:
Maybe throw the back of the sled up un the air, pull the belt, and see how everything spins. Should spin track by hand quite easily. There has to be excess drag somewhere.
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Already done. Everything spins great. I'm also having a problem with my power valve servo. I've been revving it up on the lift to see if the servo opens and it doesn't, I get 7 flashes when going really fast or when coming back down to an idle but the valves have to be working because it gets upto 8500 rpm.
 
Not necessarily, I had 2 pull thru's on my SRX and didn't even know it. Still pulled 8400, but my mileage didn't drop like yours. Has this sled always been thirsty for gas ?
 
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ssrrxx said:
Not necessarily, I had 2 pull thru's on my SRX and didn't even know it. Still pulled 8400, but my mileage didn't drop like yours. Has this sled always been thirsty for gas ?
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No was pretty good last year. At least 12 MPG. I know my valves aren't pulled through just went through them. I raised the needles over the summer as per Don's recommendation, would raising the needles to 3.25 from 3 have that big an effect on the gas mileage?
 
I don't think it would cause that much of a drop, if your plugs are not black, I don't think your problem is fuel related. Are you measuring your mileage by the gas gauge or how much fuel you added?
 
02YamiSxViper said:
No was pretty good last year. At least 12 MPG. I know my valves aren't pulled through just went through them. I raised the needles over the summer as per Don's recommendation, would raising the needles to 3.25 from 3 have that big an effect on the gas mileage?
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no, something else.
 
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