Real world Viper jetting?

thegrizzly1

thegrizzly1

Previous sleds:
Joined
Jan 6, 2009
Messages
56
Age
50
Location
Chisholm Mn.
Looking for real world setup people have for their "stock" vipers for elevation around 1500ft.

I purchased a 2003 mountain viper with a bunch of mods done to it, including SLP triple pipes. I want to go back to stock primairly for mileage reasons. I already picked up stock exhaust and started second guessing myself on jetting.

Generally, when piping a sled, I've always seen recommendations for jetting "up" one or two sizes or going a little richer.

With the triple pipes (that came with the sled) I have 152.5 mains and #45 pilot jets. According to a stock setup for my elevation I should have 156.3 mains with a stock exhaust. I did check my plugs, and if anything I was on the rich side with the triple pipes. I've heard all manufactures jet a little rich from the factory, but this is a big swing. I'm afraid if I go for the 156.3's that are called for, I'll be way to rich.

For those of you in a similar elevation, what are you running?
Any thoughts why it would seem so rich triple piped with such lean jets?

Thanks in advance for any help.
 
Last edited:

According to this chart, i would jet for zero degrees, that should have you covered from almost all riding days. A 156.3 main with a 45 pilot will have you set, you don't wanna run a viper too lean due to higher compression nature of the motor as well as more timing versus other yamaha engines. I personally run the fuel air screw a little lean and a fatter pilot to rid the viper of the off idle bog, just a personal preference.
 
156.3 mains, 45 pilots but raise the needles even with the stock pipe or you can and likely will have problems with todays lousy gas.
 
staggs65, it was properly vented to the airbox. I made the mistake last year of not hooking up the vent line to the airbox after a carb cleaning and it would really fall on it's face. Way to rich. I had the sled at the give away ride in Muni last year and it ran just fine.

Guess I never thought of them being drilled. Didn't look modified to my eye but I suppose the only true way to check would be to measure the orifice.

So I take it many of you at a similar elevation are running the 156.3's per the oem setup?
 
Last edited:
I know I'll have to pull them apart again for the yearly carb cleaning. I'll double check then. Just got out of another shoulder/rotator cuff surgery, so it will be a while before I can pull apart.

Does anyone know if the jet size # correlates to a physical dimension of the opening? I.E. a 156.3 = .0xx" orifice?

If it turns out they're not drilled and are in fact 152.5's, any other thoughts on what would cause an apparrent rich condition with such lean jetting? This sled is a new to me sled more or less, but it doesn't have anything like a dial-a-jet or ATTAC/Tempaflow.
 
Just thought I'd follow up on this. I'm back in enough shape to be doing some work on the sled again. Pulled the carbs off last night. The mains were a little mangled from previous owners, but I think they were in fact 162.5's. Those buggers are really tough to read! The pilots aren't much better.
Thanks for all the help.
 
I bought myself a magnifying glass at the local hardware store for a dollar,it's about 3" in diameter and it saves me from having to squint trying to read them tiny numbers.I have second guessed myself many times and finally found the magnifying glass in the bargain bin,saves a lot of screwing around.
 
You must log in or register to reply here.


Back
Top