SX/SXi/SXi Pro 96 SXI with 93SX motor with Dual Mikuni 38 SBN's Bogging Badly

[Gunner_626]

Hey guys, my dual 38 SBN's on my SXI are bogging really bad after I decelerate from going fast for a long time. They especially will bog horribly after accelerating to jump a wave and then after I land and hit the throttle. These carbs are off of a 2003 Kawasaki SXR, I just had them professionally rebuilt 2 weeks ago with genuine kits, and they bogged exactly the same before and after having them rebuilt. They are jetted to spec for my motor and the high and low speed screws are set to stock specifications.

Heres the weird part that I want to mention. On a full tank of gas these carbs bog badly after hitting the throttle right after a fast decleration, but once I burn a half of a tank of gas or more, the ski runs perfectly all the way an empty tank, no bogging what so ever. This has happened every single time I have ever taken the ski out, less than a half of a tank of gas and she doesn't bog at all. But more than a half tank and it bogs horribly.

Any advice is greatly appreciated. Scott.

 

[turboracer]

Do you have some detail on your set up? Pipe, head, prop, your weight...etc...Mikuni manual has a suggestion at the end to double up on the anti siphon valves if you are having a problem like this. Have you tried this?

 

[Gunner_626]

Hey, I read that in the manual, but to tell you the truth I have no clue what the anti siphon valve thing is, or how to double up on them...

West Coast 185 psi head, stock pipe, Skat Trak prop, 155 lbs

 

[turboracer]

When you open your carbs to change the jets, you have to remove a metal crescent shaped metal piece that is held down with 2 phillips head screws. On the back of this crescent shaped plate is a very thin piece of plastic held down with a small phillips head screw and small metal plate. That plastic is the valve. On page 7 of the manual you will find a diagram. Third line under the high speed needle labeled check valve. You may want to just check the condition of the ones you have. If they are bent or damaged they wont seal well against the plate. If not damaged, get 2 more of those( they come in the rebuild kits). Stack them 2 in each carb. This will make it harder for the engine to create enough vacuum on closing the throttle to pull extra fuel from the bowl. No promises on this being the fix, but it's worth a shot. Good Luck!

What jets are you running? What pop off?