cruiser starts strong, but then...

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May 16, 2010
Madison, Wisconsin
Cruiser starts up strong but then within about 3 seconds starts running rough and blows lots of black smoke. Can't stay running. Wait a half hour, then I can start it strong again only to have it run rough within a few seconds. I have gone through all my ignition components and figure it is carb related at this point. Got a rebuild kit on order.

Anyone else experience these symptoms? What ultimatly was your solution?
You can go two ways on this. Your ignition could be failing to burn the fuel or your getting too much fuel. Either way you get big Black smoke. What do have for history?

Things to try: bypass your dropping resistor going to the coil and then start it. Don't leave it like that.
When you start it give it enough pedal so that the engine would run at 1500 RPM. This will use different paths in the carb.
I have seen condenser failure do this.
Give some description of your engine. Stock?
Detailed smoke facts

Steady white smoke; warm engine; any air temperature. This is bad news. The engine's coolant is leaking into the combustion chamber and creating a steady flow of steam. Caused by a leaking head gasket or a crack in a cylinder head, most commonly in the exhaust port area. Usually requires serious surgery on the engine.
Puff of white smoke during cranking, before the engine starts; cold engine; gas or diesel. This smoke is unburned fuel vapor being pumped out the exhaust pipe. The white is tiny droplets of fuel. In a gas engine, the spark plugs aren't firing, or the fuel mixture is too rich to ignite. It may mean the choke
plate is stuck closed, or a load of bad gasoline. In a diesel, this cranking smoke indicates defective glow plugs, but may also come from low compression caused by worn rings or valves.
Gray smoke seen only briefly when the engine first fires up; gas or diesel. This is engine oil that has gotten into the cylinder head combustion area or onto the back side of the exhaust valves as a result of worn valve stems or seals. The oil smolders and smokes at first, but then burns off when the engine gets running, and the smoke disappears. This can be an early warning sign of serious trouble. But if the engine isn't using a lot of oil, it's not a fatal condition.
Gray smoke when the engine is warmed up. Usually appears when the engine is accelerated and may be especially notable when the engine is idling. This is unburned oil drawn into the combustion chamber past worn rings or valve guides. In the best case, the oil is just too thin (old oil, wrong weight) and is slipping past the piston rings and valve seals. The oil sump may be overfull. The cure is a simple oil change. But that won't solve gray smoke resulting from a worn engine. In the worst case, gray smoke means the engine needs replacement or serious internal repair.
Black smoke in a steady stream; cold engine, gas or diesel. Black smoke contains carbon particles from fuel molecules that have broken down but have not burned completely. On gas engines, this can mean the
choke is not fully opened, the air filter is badly clogged, the ignition system is not firing every time or the carburetor or fuel injection system is set too rich. Normally fixable without tearing down the engine. On diesels, black smoke during warmup can result from a plugged air filter. It can also be a sign of weak compression in one or more cylinders or a maladjusted injection system. In gas and diesel engines, black smoke means excess fuel in the combustion chamber,which washes vital lubricating oil off the cylinder walls. Get it fixed quickly:eek::eek::eek:
White smoke= Water
Blue smoke= Too rich
Black= Possibly Oil....

Worth doing a compression test before anything else......

Hey Nails!

You need to edit here.

You've accidentally transposed your Blue/Black symptoms.

Wow. Great stuff here. Thanks guys.

When I take the cruiser out for a spin or accelerate beyond 1500 RPM's it runs real nice and smooth. So yeah maybe it is getting too much fuel. How can I tame that down?

I had it timed very well, but if I advance by turning the distributor or sucking on the vac advance tube, the engine runs smoother at idle but black smoke is still coming out. Again, higher revs clears it up.

F Engine is all stock and original to the cruiser. 2 barrel stock carb. EGR emissions system is gone. OEM consumables as much as possible. Don't know the history on valve adjustment... figured I would do that soon. Recently changed the air filter. Manual choke. Don't know history of PCV valve. Been driving it for the past 2 months with no problems... all of a sudden this started.
I don't know much about the stock carbs but if it started doing this all of a sudden it might be something like:
Carb float stuck or a hole in it.
Carb passage blocked.
There should be a site window on the carb for fuel level. What does that look like?

Check the fuel filter and probably rebuild the carb.
Another note... tonight while it was idling i took the air cleaner off and looked down the carb intake. I noticed that in one barrel there was a nice even spray or mist being created while on the other side it was just dripping. Is this normal? I revved the engine up, and still just drip drip drip from one side...pretty heavy stream but not a spray like the other.

Fuel filter is transparent and it has sediment collecting in the bottom. Fuel window on the carb indicates it is full...maybe too full. Is the fuel line suppose to be in the middle of the window?
I was going to rebuild the carb myself, but this would be my first time aside from rebuilding motorcycle carbs. I will consider a pro... who are Jim C. or Mark A?

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