Hard Starting

[TownsendsFJR1300]

This is a Primestart device for a four stroke model. Similar, but different, to the ones used on a two stroke.

Thanks.. Do you know what (generally-less volume?) would be different and why between the 2 and 4 strokes? (just curious)

[boscoe99]

Thanks.. Do you know what (generally-less volume?) would be different and why between the 2 and 4 strokes? (just curious)

Sorry, I don't have a clue as to why the differences. Other than a two stroke has the ability to create pressure pulses to help move gasoline whereas a four stroke has to depend on a pressure differential created in the carburetor.

[99yam40]

Thanks to the great drawings I think this problem is about solved. Looks like the thermal enrichment device is not working.

Thanks to everyone.

the thermal part is what shuts off the fuel flow after the motor warms up.
So I do not see how that could be the problem with motor not starting when cold.
problem with the thermal heater would be a problem with it running too rich after warm up

[TownsendsFJR1300]

Sorry, I don't have a clue as to why the differences. Other than a two stroke has the ability to create pressure pulses to help move gasoline whereas a four stroke has to depend on a pressure differential created in the carburetor.

Thanks........




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[rodbolt17]

the carbs for a two or 4 stroke work identically.

it uses a colum of air that at se*****l is about 14 miles high.

pulse pumps work on both two and fourstroke engines.

they have been around for years.

most large 4 stroke motors use another carb circuit called an accelerator circuit that most two strokes do not need.

[99yam40]

I believe this was referring more to the prime start enrichment system than the way the carb itself worked

[boscoe99]

Where does a four stroke carburetor get the air pressure pulses from to activate a pump?

[TownsendsFJR1300]

I believe this was referring more to the prime start enrichment system than the way the carb itself worked

Yes it was.

Is the prime start any different (basic operation) between the 2 and 4 stroke?

I would think just the volumne of air going thru ANY carb(cranking), (2 or 4 stroke), with the prime start "activated" would allow extra fuel to be sucked in

Just an educated guess...



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[99yam40]

I am not sure if the 4 stroke prime start enrichment system uses a diaphragm pump like the 2 stroke, mainly because I never looked at a 4 stroke one

[rodbolt17]

the 4 stroke prime start does not need the fuel enrichment pump.
it uses about 1/2 the fuel a two stroke does for each revolution.
but the principle is identical.