4hp 4 stroke Yam

[RedBaronj]

Help!
Yamaha 4hp . Engine has only about 15 hrs running time. Runs only with the
choke pulled out. Stripped and cleaned carb with carb cleaner & compressed
air, replaced fuel filter, symptom still persists.
Would be greatfull for any ideas.

[Rangerspeedboat]

If it only runs with the choke out then its running lean, my guess would be an air leak after the carburetor. Does the carb have a gasket on it?

[Frosty]

This is main jet. The choke restricts the air pulling fuel through the half dirty jet.

Water in these tiny carbs is the biggest problem and leaves white calcium that will not blow out.

[RedBaronj]

Tried that before with jet cleaners.
Thanks anyway.

Regards

Red

[kenJ]

I agree on the plugged main jet. Quite often it takes poking with a wire followed by the carb cleaner and air to unplug them. I've seen one or two so bad that the jet was completed blocked, looked like solid metal. I wasn't till I started poking did the jet become visible.

[PAR]

Ditto the jets, but also the bleed and other passages inside the carb need to be chased with a "sized" wire orifice ream. You can run carb cleaner through it all day, but if it's the over the counter stuff, it's weak and not very effective. The good stuff is 10 times as strong and the carb needs to soak in it for hours.

Since your engine has such low hours on it, it's very likely you have an obstruction in one or more of the passages. Depending on the year of your engine, you may have deteriorated fuel lines and rubber parts, that are depositing little bits of hard nuggets into the fuel stream. These can drive you nuts as they can be so small that you can't see them, but 2 of them can partly block a vent or other passage, making you run super lean.

Buy a set of orifice reams and carefully go through the carb with the appropriate sizes, after a long soak in cleaner. Rinse then blow out. It would be wise to examine the inside of the fuel lines for crumbly surfaces, which is a big tell.

[bruceb]

Did it ever run correctly? Also, does it run any better if you keep pumping the fuel line bulb? B