Awful gas mileage.

Is the carb vent line on the air box ? Had a fuel mileage issue on dad's viper venture and when dealer cleaned carbs and power valves, they forgot to plug the line back onto the air box. This makes the sled run rich, which from the plug pictures might be the problem.
 

Vent line is plugged in. I did a search on this forum and that was the first thing that came up so that was the first thing I checked.
 
loosen up the choke cable. see if the plungers are held open a bit.
 
If that's not it, adjust the floats. I've seen a lot of people having mileage issues on 10+ year old sleds lately and when my '01 SRX did this I messed with so many things like clutch settings, the TPS, jetting; anything and everything people here told me, then one day last March we were riding in 35+ degrees and my sled dropped down to 5-6 MPG and wouldn't run worth chit. That's when I kept popping the hood to look at what might be causing such a bad low speed bog and with the engine running I noticed some gas dripping out the over flows. Yanked the carbs, tore them down, bent the tang on the floats, dropped my needles all the way down (because it was warm and I was already in there) and threw it back together. "Holy hell" did that thing snap to life!!! Pulls to 90+ without so much as a miss. Been so much better on power throughout the entire throttle range this year and I'm averaging 11-12 MPG no matter the temperature!!! :brr
 
Wizard said:
If that's not it, adjust the floats.
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Ok....Thats the one thing I did not adjust or check. Everything looked good visually. The service manual recommends 11.3-15.3 mm, thats alot of room for error. Is there a way to check without taking the carbs off? You mentioned watching fuel come out the overflows. What did you set your carbs at, is there a happy medium 12.5mm?
 
I'd never looked very close at the carbs because on colder days up to that point it seemed to run fine up to about 60 or 70 when it would sometimes start missing sometimes not so much. I was assuming it was something else altogether the whole time. I was double and triple checking the servos motor functions, cable play lengths, looking for pull throughs and dirty sticky power valves; all that sort of stuff. It was dumb luck seeing the over flow and changing the float levels was just a hunch. I was 7 hours from home (3 families rented a house in Iron River, Mi. over Spring break), I didn't have float valves which I assumed may be getting old and thus worn out, and we were all going for another ride the next afternoon. The ride we were on was so stinking bad, I had to try something! So,I set mine at the 11-1/2'ish mark and hoped for the best. It worked, the next ride was a blast and I've not been into the carbs since. If you can find brand new float valves, I'd suggest what you said, set them in the middle of the range. My sled only had just over 6000 miles when it began acting up, and while I don't know how long float valves should last, once I went to the minimum float level setting, mine are still closing gas off like they should.
 
Wizard said:
I'd never looked very close at the carbs because on colder days up to that point it seemed to run fine up to about 60 or 70 when it would sometimes start missing sometimes not so much. I was assuming it was something else altogether the whole time. I was double and triple checking the servos motor functions, cable play lengths, looking for pull throughs and dirty sticky power valves; all that sort of stuff. It was dumb luck seeing the over flow and changing the float levels was just a hunch. I was 7 hours from home (3 families rented a house in Iron River, Mi. over Spring break), I didn't have float valves which I assumed may be getting old and thus worn out, and we were all going for another ride the next afternoon. The ride we were on was so stinking bad, I had to try something! So,I set mine at the 11-1/2'ish mark and hoped for the best. It worked, the next ride was a blast and I've not been into the carbs since. If you can find brand new float valves, I'd suggest what you said, set them in the middle of the range. My sled only had just over 6000 miles when it began acting up, and while I don't know how long float valves should last, once I went to the minimum float level setting, mine are still closing gas off like they should.
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Alright thanks. I was already looking in the carbs, I already went through them, I just never thought of the floats. I ended up just getting new inlet valve assemblies, o-rings for the inlets and o-rings for the fuel screws. While I'm in there I might as well cover all my bases. Someone on this forum also mentioned that 14mm is the perfect number for setting floats, I'll set them there, Since you measure upside down I think 14mm means less fuel in the bowl than 11.5mm. Hopefully this solves my problem. Buying double the gas sucks!
 
im pretty sure your needle setting will be your issue but let uss know after your next ride
 
I am getting bad mileage on one of my vipers too. I just went through everything tonight. Re-cleaned carbs, set floats and pulled reeds. I had a chipped reed in all 3 cylinders. Hoping this is the problem. Might be worth a check for you. Also, make sure the oil pump cable guide didnt get pulled out of the adjuster, making the cable pull too far.

Is the sled performing any different at all from last year....hard to start, bogging out of the hole....anything?

Keep us posted on what you find!
 
Just checked the floats, they're are in spec. Ranging from 12.8-14.1mm. Suppose that's not my issue. I'm hoping its a needle and or seat problem. The sled has a bog or hesitation in the mid range, around 5000 rpm. Felt like I had to give it more throttle than I should to get it out of that range.


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1 full clip will be a average of 1 gallon more of gaz for the same ride ...;)! so u can do the calculation
 
modsrx said:
1 full clip will be a average of 1 gallon more of gaz for the same ride ...;)! so u can do the calculation
Click to expand...

I only went up .25 from stock, so isn't that only a litre? Or are you saying going up .25 would burn a gallon?


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just to look at your plug its pretty easy to see that your needle setting are at wrong position ,unless u did something to your vent that goes to the air box ...thats sled must be running not very well in midrange
 
modsrx said:
just to look at your plug its pretty easy to see that your needle setting are at wrong position ,unless u did something to your vent that goes to the air box ...thats sled must be running not very well in midrange
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You are correct sir, it runs like SHITE! I raised my needles to be safe, raising my needles was recommended on this site to prevent viper burn down. I'll change my needles back to 3 and see if that helps. I really just want to not worry about gas every 90km
 
its hard to get the correct jetting with someone who is not in the same elevation ....i know viper are prone the burn down but i think its not related to needle setting
 
Did you ever check your reeds? How does your piston wash look? Airbox have alot of fuel in it? Are your carb slides syncronized? How about plug chops to find out where you're rich since your plugs are showing rich. I have my needles set to 3.25 and still get 10-12 mpg on average on hard pack and I'm a pretty aggressive rider.
 
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