I'm going to be digging into the carbs on my Vipers and I'm considering going up a jet size and raising the needles to the 4th groove if they are at stock settings just to be safe during cleaning. Anybody else running stock Vipers up a jet size? Did you just go up a size on both the pilots and the mains? Plugs have looked fine in one Viper last year and the other is new to me this season. My only reasoning in doing so is to be on the safe side now that ethanol fuel is the norm these days. Is the the majority here running the stock jetting these days in stock sleds at near sea level altitudes? I don't want an overly rich pig but I will sacrifice a little for protection... though I'm not sure if it's an issue with the Vipers.... though I see Yamaha recommends it in the manual when running ethanol fuel. I am going to go ahead with raising the needles a bit due to Vipers getting lean in the mid range but look forward to any comments on the jetting.
Lot's of great info on the site. I have been reading this site for quite a while and learned a lot about the Vipers.....maybe too much...to the point of expecting one of them to blow up this season.
Lot's of great info on the site. I have been reading this site for quite a while and learned a lot about the Vipers.....maybe too much...to the point of expecting one of them to blow up this season.
Last edited:
FJViper
New member
My Viper is stock right now. As soon as I get it in the garage for pre-season maint. I'll be raising my needles to 4th clip. Most of my riding is done on the pilots(which are set at 2 turns out to take care of an idle hang) and the needles. Haven't heard of anyone upping their mains unless your running pipes. You may have seen the article by Mr.Viper that thoroughly explains the jetting circuits and what you can do to prevent a lean burn down. Don't know if anyone has any experience running the needles a little richer on a stock Viper but I would imagine it should pull a little better unless it's 45* out. I'm sure someone will chime in on this.
--Brian
Poss. snow showers this week in NH. Things are shaping up!!
(dammit!)
--Brian
Poss. snow showers this week in NH. Things are shaping up!!
(dammit!)I have read the posts from Mr.Viper on the needles which headed me to going that route. I just haven't seen a whole lot on going up on jetting due to ethanol fuel on stock sleds as Yamaha recommends. On a couple other brand sleds, I have gone up on jetting on one and run the ethanol wire on the ECU on an EFI sled to be safe. Vipers are a little new to me. Appreciate the info boys. 
the main jets are not so much into play on a viper, or as much of a problem. Its the mid range cruising circuit(needles) along with the increased ign. timing and a head that does not do a good job at removing the heat from the mag cylinder. The compression is also higher in the center and mag cylinders.
depending on how cold of a temp you ride in you can go to 4th groove with a shim above and below the clip or 4th groove with both shims on top which will be slightly richer, but not as rich and possibly blubbery(rich) running if your in warmer temps.
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depending on how cold of a temp you ride in you can go to 4th groove with a shim above and below the clip or 4th groove with both shims on top which will be slightly richer, but not as rich and possibly blubbery(rich) running if your in warmer temps.
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