Carburetor problems and how to repair them.
While compression and spark are necessary for an engine to run, the spark is just a glimmer without the fuel for an explosion to push the piston down and turn the crankshaft!
The first check we all probably make is for the presence of fuel at the hose or line entering the carburetor.
This is a great first check but barely scratches the tip of proper fuel flow as the Real Deal takes place inside the Carb.
* DON'T use Starting Fluid or Ether to Crank or Test Your outboard motor ! *
On a 4 stroke engine starting fluid will wipe away any lubrication on cylinder walls and allow easy scoring.
On a Two-Stroke outboard all internal parts of engine are lubed VIA oil mixed with the fuel. Starting fluid wipes away all the lubrication present on crankshaft, connecting rod, bearings, piston skirts, rings, etc.
This is a good way to add a years worth of wear and tear to your motor in a matter of minutes!
For testing etc. use a oil-squirt can wit gas and oil mixture in it and NOT starting fluids or ether.
I'll try to simply explain what has to happen inside the carbs for any engine to idle and run correctly; any diagrams will be generic, but basic idea and principles apply to all models.
Notice that needle and seat inlet is the first place the fuel has to pass through.
It is only a valve that the float opens and closes as the level of fuel in the bowl raises and lowers the float. If a motor has been in storage without draining the fuel(which turns into a sticky substance)then it is possible for the float valve to be stuck shut.
No fuel can enter the carburetor in that case. That same sticky gunk can of course cause valve to stick open causing the carb to overflow with fuel. In either case removal, disassemble to clean,and renew parts as needed will be necessary. Heres a picture of a carburetor bowl removed from a motor sitting up for 4 months with fuel left in carb.
The brownish, black gunk is the oil left after gas has evaporated.
Fresh fuel will dislodge the gunk in pieces and start plugging main jet if motor is used in this condition.
The only way to clean this carburetor is disassembly and soaking in some carburetor cleaner or Gunk.
The main jet is right in the bottom of bowl, a little off center.
Pictured below is a gummed up carburetor that's been removed from a motor that was stored for a couple months with fuel left in carb.
Of course the gaskets are compressed, distorted, and should not be reused.
Attempting to remove the main jet in this carburetor without first soaking it in a carburetor-cleaning cleaning solution, or Gunk will probably destroy the jet.
Soak it an hour or so and then remove main fuel jet.
Never try to clean or open up any jets or passages in a carburetor using a piece of wire or drill bit.
Soaking, rinsing, and blowing all passages clean with compressed air is required for a properly functioning fuel delivery system!
Also shown is an old screwdriver carefully ground to fit closely in hole to remove the main jet. The tip should be thick enough to fit tightly into slot of jet and same width as hole.
Core plug removal is often necessary to clear idle passages etc. you can't see. With a little care and attention, it's a snap too.
Click here for a page on fuel flow and reed valve function.
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