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1990 Nissan NS5B what is this button?

R

rbc123

New member
New to me NS5B year 1990.
Front op panel has choke, kill button(not emergency off switch) empty hole with rubber plug then a push button (missing rubber cover). When I push button gas leaks out,push again and it stops. The button leads to a fuel line that goes to a Y connector. One part of Y is this fuel line,other part leads to fuel filter then to carb. The leg leads to a manual shut off at the fuel tank. I have looked in parts manual but it does not show this button? What the heck is this button?
Cleaned carb but couldn't get screw out that holds float. Tried to start engine but it will only run on the fuel I spray into intake. I assume I need to take carb apart again and clean float valve.
thanks for any help
RBC
 
Sounds like you have a 5BS, which can also use an external tank.
What method did you use to "clean" the carb? You Must completely disassemble it (including float valve, jets and emulsion tube nozzle), and do a 4-hour soak in real carb dip, followed by a liberal blow-out with generic carb spray.
 
It is a NS5B with internal tank.
I took carb completly apart and did also finally get float screw loose. Carb was clean to start with but also used pressurized carb cleaner. When I took it apart second time to work on float there was no gas in float chamber. So I am pretty sure that is where no start problem is. The fuel pump diaphragm looks OK. Not sure how that works.
But would really like to know what that push button is for. I will try to take it apart today.
thanks for the reply.
RBC
 
Spray cleaner is not aggressive enough to clear small passages. If they are clogged, you will need a soak in carb dip.
The pump diaphragm works on alternation pressure/vacuum from the crankcase, just like all small 2-stroke motors do.
It is not a push button. It is a connector for external tank. That model can use either internal or external tank.
 
Paul, thanks for your help. I got the float screw free and cleaned out area. I think maybe float needle was stuck.
I also removed ext. tank line and installed line from int. tank thru filter to fuel pump. Couple of pulls she started. Just need to put in tank to check water flow.
RBC
 
Bad idea to start -- even for a second -- out of water. You may well now need a wp kit. The rubber impeller will immediately stick, melt, and or burn in the stainless cup and liner. But at that age, it may have needed one already. Be advised that if you have a metal internal tank, they are NLA, so keep it in good condition -- no rust. If ever you need a new tank, it will be plastic.
 
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