yamaha 4sj carburetor problems

[munderwood62]

Yamaha 4sj four horsepower engine sat for 4 years without running. It would run briefly when fuel was poured into carburetor. I disassembled & cleaned carb with spray carb cleaner, the carburetor looked new inside. The engine probably only has 40 hours run time on it, used on a sailboat for a short time. Reassembled replacing the two diaphragms & gaskets next to diaphragms. The engine then started but would bog when throttle was applied. The engine would run at higher rpm with the choke 3/4 on. I disassembled carb again & soaked the metal parts in Berrymans Carburetor Cleaner thinking something must still be plugged up. Reassembled the carb and started the engine, starts on the first or second pull but again, bogs when throttle is applied. Put choke 3/4 on and it seems to reach full throttle but doesn't idle down low enough to shift without slamming into gear. Still seems like it's starved for fuel if run with choke off. Fuel flow from the fuel tank is more than adequate. Can you offer some advise?

[boscoe99]

My experience has been that it is beneficial to completely dismantle the carburetor to the extent that you can do so and to then clean it in a heated ultrasonic cleaner. Using a good cleaner of course. I prefer the Yamaha brand. Maybe run a piece of soft copper wire into any orifices to try and rod out any debris. Blow out all of the passageways of the carburetor to make sure they are free and clear. May jet some water under pressure through them as well to visually verify the passageways are open.

It sounds to me like yours is still clogged.

[zenoahphobic]

Try with cap off fuel tank to be sure that fuel continues to flow.

Make sure your float and seat not holding fuel level too low.

To verify restriction of fuel, does the engine run better with the choke a little on?

Had this symptom with a Honda motor until it was realised that there was a neatly hidden vent screw in the cap that needed to be opened. (Put there to stop fuel running out when tilting)

[BQUICK]

You need to pull the jets (idle and main) out and look thru them. No longer does soaking and blowing out with air do it like the old days when it was just gum and vanish.
Ethanol fuel leaves a white crust that has to be physically reamed out. I use a piece cut from my wire brush to clear when even after cleaning and blowing out to no avail.
Ultrasonic should also do the trick but for one little carb probably not worth it....

[TownsendsFJR1300]

+100 ^^^.

Pull the main and idle jets fully out. If you can't see light thru them, that "cleaning" doesn't count..

Putting it into choke is richening up the mix, no idle is a clogged idle jet..

Your carb is simply clogged up..