yamaha 3 cyl prime start enrichment system

[99yam40]

Can someone explain how or if the Yamaha prime start/ enrichment system sends fuel to all tree cylinders when the system looks like it is only attached to the center carburetor? Does this system only send extra fuel to the middle cylinder allowing the top and bottom cylinders to run lean during start up and warm up? The old choke systems always closed butterflys on all the carburetors, but I do not see how the new prime start enrichment system could enrich all the cylinders.

 

[rodbolt]

Re: yamaha 3 cyl prime start enrichment system

yes
look very carfully behind the oil tank at the 6mm gray hose from the crankcase to the middle carb.
this is the enrichment pump fuel pump pulse line.
behind that cover that the red plastic manual overide is a small pulse type diaphram pump.
when cold starting this pump supplies fuel from the bowl,through the thermal valves open needle and, via the small gray tube from the middle carb to the upper stbd side of the intake, to the passages in the intake manifold for all 3 cylinders.
as the engine runs voltage is supplied via either 12V or the lighting coil, depending on model, to expand the wax pellet in the thermal valve. as the pellet expands the needle extends closing off the enrichment passage.
mostly if properly maintained and setup it works very very well.

 

[99yam40]

Re: yamaha 3 cyl prime start enrichment system

yes
look very carfully behind the oil tank at the 6mm gray hose from the crankcase to the middle carb.
this is the enrichment pump fuel pump pulse line.
behind that cover that the red plastic manual overide is a small pulse type diaphram pump.
when cold starting this pump supplies fuel from the bowl,through the thermal valves open needle and, via the small gray tube from the middle carb to the upper stbd side of the intake, to the passages in the intake manifold for all 3 cylinders.
as the engine runs voltage is supplied via either 12V or the lighting coil, depending on model, to expand the wax pellet in the thermal valve. as the pellet expands the needle extends closing off the enrichment passage.
mostly if properly maintained and setup it works very very well.

Thanks for the info!
There is no oil tank because this is a premix motor, but there is a line from the center part of the crankcase area and a line from the center carb to the upper stbd side of the intake.
So, I take it that the line to the upper stbd side of the intake goes to some internal passages in the intake manifold for all 3 cylinders?
Does the hose from the crankcase to the middle carb provide pulsating pressures to the diaphram to pump the fuel to the cylinders just while the motor is turning over?

 

[Dunaruna]

Re: yamaha 3 cyl prime start enrichment system

Woops, wrong thread

 

[rodbolt]

Re: yamaha 3 cyl prime start enrichment system

sorry about the oil tank but as yamaha has made inline 3 cylinder motors from 30 HP to 90 HP both with and without prime start or oil injection I gave you a generic thing as you thoughtfully left out the model number.
note to self, from now on out rodbolt wont reply to ANY thread without a proper model number designation.
that outta about cover it.
folks ya gotta remember, your lookig at your engine, we are looking at a monitor and a keyboard.

 

[Jethros]

Re: yamaha 3 cyl prime start enrichment system

I am patiently waiting on the manual for a '02 60hp but in the meantime... I am not getting any volts when I call for it with key pushed in and ignition on. Do you have any suggestions what could be failing my manual should be here saturday but have the time to work on it today.

 

[rodbolt]

Re: yamaha 3 cyl prime start enrichment system

jethros
are ya reading challenged?
if so the manual aint gonna help.
start a seperate thread and POST your model number.
if its a USA market motor I can tell you why, or maybe why not, your getting nothing on the blue wire .
either way your manual wont describe it. trust me.