Sport Jet 120 - Fuel Pouring out of Bottom Carb/Lacks Power

[Frsmith2]

Folks,

Here's what I got, looking for direction as to where to begin my diagnostics:

Sport Jet 120 on a Regal Rush XP. Ran beautifully last season after replacing the ENTIRE ignition system. Last time it ran perfect was Sept. 2012 as the season was ending.

Took it out two months later for a warm Thanksgiving. Started hesitating at WOT. Fuel from Sept. was high octane and had stabilizer in it. Noticed at the time the bottom carb was wet near the throat and sound actuator.

Removed carbs, cleaned and installed new needles and gaskets. Put on this week and test drove. Seemed to idle fine but would bog/hesitate at WOT. Fuel still coming out of the mouth of the bottom carb.

When I was cleaning the carbs, the bottom vent was plugged but I cleared that out already.

Boats out of the water and ready for me to dig in...before I went crazy, looking for any direction on how to prioritize.

Thanks all.

 

[pnwboat]

Re: Sport Jet 120 - Fuel Pouring out of Bottom Carb/Lacks Power

First thing I would check is compression. Low compression will cause many symptoms. If compression checks out OK, then I would take a look at the carbs.

Since you mentioned that you have fuel coming out of the carbs, you may have a needle valve issue. Best way to check if the needle valves are closing properly is to squeeze the primer bulb (if you've got one). The bulb should get firm after 4 or 5 squeezes. If it doesn't, and fuel starts leaking out of the carb, you've got a needle valve that is not sealing properly. Make sure that there is absolutely no debris in the fuel. An inline fuel filter between the fuel pump and carbs is a good idea.

If the needle valve is leaking, I would also take a close look at the float level adjustment (you said that you replaced the needle valves themselves). Especially if you have the black foam type of floats. I've had quite a few of these floats when adjusted per the factory specs, (float should be parallel to carb body when held upside down) they leaked even with new needle valves. I found that if I adjusted the floats so that the free end of the float was about 1/16 - 1/8 inch farther away from the carburetor body, they worked just fine. I suspect that the float has lost some of it's buoyancy due to age and by adjusting it like this compensates for it. I've tried ordering new plastic floats, but the piece that pushes against the needle valve is plastic and you can't bend it to adjust the float level. They're not much good as far as adjustments.

Double check the fuel bowl vents again. Make sure they're not plugged. If you have a hoses that connect to the vents, make sure that they aren't plugged either.

If the needle valves aren't leaking and pass the primer bulb test, take a look at the fuel pump diaphragm. Make sure it's in good shape and doesn't have any holes and is not hard and stiff. It should be rubbery and flexible.

If you have a fuel primer solenoid instead of a mechanical choke plate, check to make sure the solenoid is not leaking fuel into the carburetor throat. Usually when they leak, it affects low RPM operation. It kinda floods the motor. Doesn't appear this is happening in your case, but might want to check it.

 

[Frsmith2]

Re: Sport Jet 120 - Fuel Pouring out of Bottom Carb/Lacks Power

Thanks, I'll try some of this. Couple points to clarify if this helps - my floats are the plastic "orange" colored floats. Also, I don't have a primer bulb it uses an auto enrichiner attached to the top carb.

I bought a fuel pump rebuild kit and will do that anyway, so will look at it. The flow pulses slightly when cranking into a clear container but fills the container pretty quick.

The lower carb having fuel at the mouth where it shouldn't be has to be a symptom of something fun happening...

Thanks again!

 

[pnwboat]

Re: Sport Jet 120 - Fuel Pouring out of Bottom Carb/Lacks Power

If you don't have the primer bulb, I guess cranking the motor will work too. Not sure why the Sport Jets don't have one. Probably some type of Coast Guard regulation or something like that. Anyways....the orange-ish plastic floats with the metal tab for float adjustment are the one's that you want. I always do a compression check just for good measure. For what ever reason, these motors seem to be sensitive to compression issues....more so than a four stroke motor.

I would try replacing the fuel pump diaphragm. Especially if you haven't done so for several years. If you look at the general symptom, bogging at WOT, runs fine at idle, that could be a fuel delivery problem.

To eliminate the auto enrichener, just plug off the hose between it and the upper carb fuel bowl.

I would still at least be thinking about tweaking the float in the lower carb.

It's just a process of elimination. Do the easy, low cost things first. Good luck and let us know how it works.