Stock 04 Viper Center CYL Running Lean

[sledneckdon]

I have a stock 04 Viper and the center cyl is running leaner then the outer 2. Did Yamaha change anything in 04? My 03 did not have this problem. I know they added the deto sensor and I heard they reduced compression in one of the cylenders. Power valves are clean. Anyway what adjustments can I make to get all 3 cyl running toasty brown. Right now the outer 2 cyl are dark brown/black and the center cyl is light brown. I have heard of two other 04 viper owners cooking thier engines center cyl I don't want to be next.

 

[A K MtnViper]

my 03 runs rich on the pto cyl. I just went 1 step leaner on jetting that cyl only.
for riding at 10,000 feet pto 145, center 147.5, mag 147.5. Runs great and plugs look even in color. If I were you i'd just adjust the jettimg to even it out.

 

[Ding]

Sorry for stating the obvious, but . . .

1. Make sure your carb is clean.
2. Make sure there are no air leaks in the rubber boots.
3. Possibly do a leak down test to make sure you don't have a leak in the cases somewhere.

Did this change suddenly, over time, or has it always been this way?

If it is a change, I would look for the cause instead of simply making adjustments to correct it.

 

[sledneckdon]

Thanks for the tip. I am running at maybe 1000' above sea leval on the east coast with very few miles on the sled 800 max. I thought it was odd to have 1 cyl that much leaner than the others. Also, I know two other 04 Viper owners that have fried center cylenders at relativaly low miles. I will start with the jet changes. Thanks again.

 

[sledneckdon]

carbs, power valves both clean and no leaks.

 

[YamerDown]

FYI - It's the PTO cylinder with the reduced compression, not the center.

 

[sniperviper]

"Low" compression on PTO cylinder is stock on the viper. My 2002 has 120, 140, 140 psi.

check the air went hose from center carb to the airfilter box and be sure that it's open and not blocked.