journeyman
Active member
Well I just got back from Northern Wisconsin from a 2 day ride and I could use some thoughts on a current issue I have. I put on 290 miles in 2 days but my fuel mileage was terrible. Both days I rode over 100+ miles and I would make it to the 60 mile mark and the fuel light was on. I was getting about 8 MPG. That's in the piped Viper territory. My buddies 600 SRX which usually would be a half gallon better from point to point got 13-14 MPG. I had this issue last year but thought I had it cured when I found my reeds were shot, which I replaced. The only running issue I seem to have is a low speed babble like almost a dieseling sound in the pilot portion of the throttle position......4500 to 6000 rpm. Once it hits 6000 rpm and above it cleans right up and runs perfect. From a standing idle it sounds fine. My midrange and top end are good. I read all the poor mileage Viper posts I could pull up on a search and will look into those. BTW, my rings are fresh this year and my carbs are clean.
here are some of my thoughts:
1) carb vent on airbox unplugged
2) bad stator ( but I did a voltage test which was good and it starts just fine)
3) bad fuel pump
4) bad cdi
5) bad plug caps (they do seem a bit looser than usual and I saw a darker color on the plug tips) spark plugs are new too and I did foul a plug yesterday but it was caused from snow dust. I always need to turn on carb heat in those situations.
6) maybe a leaky fuel line but I would expect alot of fuel in the belly pan.
7) as mentioned reeds are new unless one is pre-maturely chipped
8 ) wire harness rub through....a couple years ago I think I had this issue causing the tach and lights to go wacko and it just went away when I hit a trail whoop and it never has happened again. That was almost 2000 miles ago.
My Viper now has 8111 miles as of today.
Any thoughts are appreciated.
here are some of my thoughts:
1) carb vent on airbox unplugged
2) bad stator ( but I did a voltage test which was good and it starts just fine)
3) bad fuel pump
4) bad cdi
5) bad plug caps (they do seem a bit looser than usual and I saw a darker color on the plug tips) spark plugs are new too and I did foul a plug yesterday but it was caused from snow dust. I always need to turn on carb heat in those situations.
6) maybe a leaky fuel line but I would expect alot of fuel in the belly pan.
7) as mentioned reeds are new unless one is pre-maturely chipped
8 ) wire harness rub through....a couple years ago I think I had this issue causing the tach and lights to go wacko and it just went away when I hit a trail whoop and it never has happened again. That was almost 2000 miles ago.
My Viper now has 8111 miles as of today.
Any thoughts are appreciated.
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If it makes you feel any better, I was out for my first ride with SLP pipes this weekend and I got 6.7 mpg. That was pretty much all medium speed (40 mph) trail riding with about a 1/2 hour of goofing around in a powder field. I obvioulsy don't have it dialed in yet (it is running really rich). I am running it setup with -20F jetting at 0 - 3000 ft... 165 mains, needle at 4 and 47.5 pilot. This week I am going to install an ATACC and hopefully that will solve the problems. I have 9000 miles on mine. I am in St. Cloud... we should try to hook up some time to compare performance. I must say, if my mileage doesn't improve I think that I will be going back to stock pipes sooner than later. I will go broke buying gas!
I would go with your #1. Vent tube not in air box.
Check the skid. Might have a bad bearing or two.
Or its in the clutches. When's the last time you did bushings or checked them? Clutches could be hanging up not giving you full shift out.
How's the rpms? Topping out at 8400?
Check the skid. Might have a bad bearing or two.
Or its in the clutches. When's the last time you did bushings or checked them? Clutches could be hanging up not giving you full shift out.
How's the rpms? Topping out at 8400?
journeyman
Active member
My clutches are good, just had them apart and cleaned. It tachs perfect at 8500 and creeps to 8700 on a long pull. I just had the rear skid out too this year and all my bearings were good. My shocks are all rebuilt too. I just feel that the strange running quality from 4500 to 6000 is the key to what is going on. I am kind of looking for other high mileage Viper owners that may have seen an issue like mine. It is still rideable, but sucks fuel like a camel taking on water. Kind of spendy.........
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viperking
Active member
If you have not previously run it with the vent in the airbox unplugged i would try that, if you didn't pipe/bigbore it i would leave the vent lines hooked up, removing them will greatly richen the sled up from what i understand on the subject
journeyman
Active member
If I remember right the guys that said they had bad stators usually experienced poor top end and hard starting with a warm engine. Neither one of these has come up. Boy I was looking up some of the parts new on Port Yamaha........a new CDI is over $600.....ouch!!
journeyman
Active member
well I think I figured it out. The air screws in the carbs are iced over. I probably did not turn on the carb heat early enough and they never melted off enough making my fuel/air mixture too rich. I rode 45 miles the day before I went up north around home and had no issues so this now makes total sense. Usually I can run until it starts to babble and then I pull over and turn on the carb heaters with a small channelock I keep in the back storage just for that reason. I was trying to flag my buddy down that day to stop because it was getting really bad and I ended up fouling the middle plug. From that point on it babbled on low end and sucked fuel like crazy. Being the sled never thawed out it never went away. I guess I'll know that from now on. Just run the heaters when I am up there. My sled has always been real finicky in snow dust conditions. Must mean my air induction is working good. LOL!!