04 Viper Fuel Economy Loss?

I

ILLYamaRider

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Mar 22, 2005
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Age
43
Location
Illinois
My 04 Viper ER I have had for 10 years and now has about 6500miles on it. I used to get about 15mpg riding pretty hard in Wisconsin. The last 2 trips has been down around 10mpg. I am trying to figure out what is happening with my mpg. Here is what I know:

- Checked compression cold and I got 120, 135, 135 (from 1, 2, 3). Everything thing I have seen on here tells me that this is about right.
- It did have some idle hang, so I did recheck my pilot screw adjustment and found that they were in about 1.5 turns instead of the 1 7/8 recommended. I made that adjustment. However, before I adjusted the pilot screws I used to find that it would have a lot less idle hang if I kept the idle speed down around 1300 instead of the recommended 1800.
- I did put on a heelclicker primary clutch kit many years ago, and it didn't effect the mpg much (just wanted to everyone to know). Otherwise the sled is bone stock.
- I always use premium fuel.
- I clean my power valves every season (about every 500 miles is all I get anymore).
- I still think it has as much power as ever and no hesitation
- I will assume there are more losses in my older track wheel bearings and such (I check them every year, and most are still good (but probably not as good as new)
- I did change this year from BR9ES NGK to the iridium version BR9EIX

Any thoughts as to where my mpg has gone? Would the idle hang really use that much more fuel? Would the spark plug change cause a decrease? I put them in hoping for some increase in performance or at least reliability. Any help appreciated. Thanks.
 
Is it possible you have a fuel leak? Ive seen fuel lines wear through before where they are rubbing on something. Like the clips that hold them down under the jackshaft for example. You can get a tiny pin hole and what will happen is it creates a bit of a mist and ends up sucking into the airbox. It's something to check anyway. Your foam airbox seal will be a little gooey If this is the case. I don't think the plugs will make an difference. Not noticable anyway. Maybe time to rebuild your clutches. Check the basic things like track tension and chain tension. Could be something in the carb too maybe go through them.

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Hard to say. The heel clickers will get ya a little but you have been running them a while know. My thoughts are Sleds older, parts are worn, gas is bad ect.... Mine are right around 12mpg on good days.
 
With ethanol in the fuel, you need more fuel for the same power output than when the sled was made 11 years ago with MTBE as the oxygenator. That's why you hear so often to raise the needles, increase jet size, open idle mixture screw (for hanging idle/lean). At least this is my understanding of ethanol.
 
Possibly float levels or bad shut off seals, too. I was getting 8'ish on my '01 SRX for a while and then it started getting even worse. Too a while to figure out it was too much gas in the bowl; eventually it showed up as overflow. Reset the levels and right back up to 12 MPG plus it began to run better again.


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Also watch out for jackshaft and drive axle bearings. And the driveshaft itself.
 
I would look at the rear upper wheels, lots of people overlook those and they may not seem loose to the wiggle but they will act like a brake and drag, with 6500 miles on it, those would be highly suspect as will be the driveshaft bearings.
 
Check orings in carbs Needle valves and fuel screws, if one is bad it Will run crappy Idling and suck fuel like crazy, bit since you have Three of them it will run better that one would think and when Open the gas it will clear up and run fine.

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