Originally posted by boscoe99
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Yamaha Two Stroke Primestart
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Originally posted by pstephens46 View Post
Where would that lead?
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from what i remember in troubleshooting my C40, when in the normal position there was no liquid fuel being pumped into the line that ran to the intake.
but when placed in the on position there was liquid fuel.
I placed a piece of clear tubing in there to see what was going on.
I asked about this happening back in 08 I think and no one could answer if that was normal or not.
So I would think that when in normal position the pump is not doing anything.
The motor just sucks enriched air/fuel mixture into the intake as long as the needle is letting fuel past
I drew some diagrams of the system back then and posted them when asking about them.
I think it was Rodbolt that said I was trying to make too much out of it, thinking too much.
I you would like I can see if I can find them again to post up here on this thread.
here is a link to that thread
http://www.yamahaoutboardparts.com/f...ystem-questionLast edited by 99yam40; 02-10-2018, 11:54 AM.
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Originally posted by rodbolt17 View Postyall be whay whay over tinking.
it is a simple pulse pump with a heated wax pellet connected to a needle. as the pellet expands it simply shoves that tapered needle into a seat and shuts off the fuel.
yep it is actually that simple.
Yamaha only addresses the needle being open or closed as far as I can tell. What about the rest of the system?
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Actually the prime start enrichment system gets its fuel from the carb fuel bowl (Center one on my C40).
I am not sure if the diaphragm is needed to pump fuel thru the needle open port, or if the intake suction would pull it along with the air or not.
the more I think about it I would think the liquid fuel would be better off being pumped(under pressure at the needle portLast edited by 99yam40; 02-10-2018, 12:08 PM.
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Originally posted by 99yam40 View PostActually the prime start enrichment system gets its fuel from the carb fuel bowl (Center one on my C40).
I am not sure if the diaphragm is needed to pump fuel thru the needle open port, or if the intake suction would pull it along with the air or not.
the more I think about it I would think the liquid fuel would be better off being pumped(under pressure at the needle port
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I have seen this done on some Yams. The screw mechanism is normally locked from the factory with some type of sealant. Sealant is broken loose without damaging the PS.
https://www.youtube.com/watch?v=toYTwg2XR-0
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Originally posted by walleye1 View PostThe only time I have had to change that diaphragm is when the engine has running issues, like popping through the intake from the timing being off.
Would be nice to have a way to remove the carburetor with the PS and then apply pressure pulses to it to see if it pumps gasoline. I once knew a gal that could probably do it but she is long since gone.
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