What would cause a carb to do this?

[Quinc]

Helping a friend install this sbn44 on his stock kawa 650 and I cant figure this out. Tried jetting from 120/140 to 127.5/150/155. Pop off is around 21psi. Tried hooking the fuel line directly to the reserve line, tried with and without the flame arrestor. Carb had the shaft and seals replaced by jetworks a few season ago, I put in new mikuni diaphragm, rest of the gaskets and check valves where new a few seasons ago and look good. internal fuel filter is clean. Ski ran fine with the oem 38 carb. any ideas? Pop off to low? carb is junk? I dont think its an air leak as it goes back to idle after letting off the throttle.

 

[Storbeck]

Personally, I never trust the last guy especially if the last guy was me. I'd be going back and rechecking the stuff I already checked. I'd go right back to the old carb. That would either eliminate the entire fuel system and any possibility I'd an electrical problem (assuming old carb does in fact work fine), or eliminate the carb as the problem (if you still have the problem with the old carb). Alternatively put a known good sbn on there or put this carb on a known good motor (might be less work than switching to the old intake)

 

[Quinc]

Only other carb I have is an sbn 38. Rest of my skis are all dual carb. But good idea on putting on the old carb and manifold to see if it makes a difference.

*Except I do not have anymore manifold gaskets. Anyone else have any ideas? Ski is also running BR7ES plugs.

 

[Quinc]

cutting plug wires and new sparkplugs it reved up normal a few times and the weird bog at full throttle is not nearly as bad. So thinking its the coil wires.

 

[orangefinger]

besides tank vent valve etc, did u check reeds ?

 

[Quinc]

besides tank vent valve etc, did u check reeds ?

New reeds, also tried with the gas cap cracked. cut the wires back some more and cleaned the plug boots but same issue. did manage to get a little backfire up through the carb one time as well.

After searching a ton of threads and youtube videos I found a bunch of videos showing the same thing and tons of different solutions. =/ New gasket kit on the way and old carb going back on.

 

[Storbeck]

For the hell of it I would check to make sure you don't have a carb with the return restrictor drilled. I'm very doubtful that's the issue, but it's easy to check. Also check the little screen and the check valves while in there.

 

[kevbo]

If its too lean you can slide your hand over the carb and at some level of restriction it will run correctly at full throttle. Kawasaki 650s have weak intake vacuum so larger main jets may be required.

 

[Big Kahuna]

Only other carb I have is an sbn 38. Rest of my skis are all dual carb. But good idea on putting on the old carb and manifold to see if it makes a difference.

*Except I do not have anymore manifold gaskets. Anyone else have any ideas? Ski is also running BR7ES plugs.

You mean the square gaskets? I think I have some if you need them.

 

[Quinc]

If its too lean you can slide your hand over the carb and at some level of restriction it will run correctly at full throttle. Kawasaki 650s have weak intake vacuum so larger main jets may be required.

I tried that to and no dice. Also tried it with a k&n filter that looks to be pretty restrictive. Buddy already took his ski home and is doing the best thing he can do. Ride it the rest of the season with stock carb then sell it and buying a superjet.