Nissan NS40C

[ventureman]

I have a 1985 nissan NS40C that won't idle. It would start with choke on, but would die after 1 or 2 seconds. Would not restart without the choke, but would start with the choke. Also, if I am fast enough with the throttle, it would run(in gear) to wide open but would cut out to lesser rpm before it hits wide open again, and then cut out again, and then wide open again, you get the idea. I took fuel pump apart, inspect,clean and looks like the diaphram is ok, but can really tell since a pinhole tear would be naked to the human eyes.
Remove carb, clean and reinstalled. Cleaned needle as well. Replaced spark plugs. Has good fire. Compression tested about 91 for both cylinders. Still problem persists. Bypass fuel pump today with no difference. Primer bulb is hard even during cut out(bog). Now, beginning to wonder if my gas is bad since it has been sitting for 6 months. Ran Sea Foam in gas and Deep Creep
in engine. Sounds like fuel starvation to me, but could it be the carb? Motor will start with choke on but would stall out seconds later even if you have the choke on. Please help, fuel, carb or gas???? Could it be reed also????
Visual inspection of the reed is ok, but what is the function of the reed?

 

[John_S]

Re: Nissan NS40C

The gas would be a quick check, but suspect the carb needs a very good cleaning. Something gummed up in the idle circuits. Use a rebuild kit.

 

[TOHATSU GURU]

Re: Nissan NS40C

What he said and your compression is low if you have an accurate gauge.

 

[ventureman]

Re: Nissan NS40C

Thanks guys, I am going to run some fresh gas to the motor this week. I think my last fill up was last August mix into about a year old gas. I hardly ever use my boat because I fish with a partner that has a nice boat. I clean the needle with some very fine sandpaper. Is this a no-no??? I am going to soak the carb for a few hours this time and see if that helps. Use a blow gun the last time. I will have to recheck my compression to be sure for the low numbers. Motor seems strong to me. Had motor since 1997.

 

[John_S]

Re: Nissan NS40C

" I clean the needle with some very fine sandpaper. Is this a no-no???"

yes, replace the needle.

 

[ventureman]

Re: Nissan NS40C

What is the proper procedure to clean the needlle? Can I buy just the needle and seat? What's the part number. I search online and it is returning part number 345-87122-0(Carb kit). It looks different though. This might be a dumb question, but I don't think I have a pee hole on this motor. Is that correct? Been running this motor this way since I bought it. Never overheated on me. Replaced impeller just last August.

 

[John_S]

Re: Nissan NS40C

Guru will have to help with the part numbers. As far as cleaning, I just soak and blow-off with compressed air. Needles usually get replaced with carb kits, but can't remember for sure if they come in the one for the 40C.

 

[TOHATSU GURU]

Re: Nissan NS40C

All 40 C models have the same carburetor and use the same kit. They all have a pee hole too.

 

[ventureman]

Re: Nissan NS40C

Took boat out yesterday, problem still persists with idle. Could only start with choke on but dies almost immediately. If I am quick enoiugh with the throttle, it would go. No hesitation at mid range to wide open, but once I throttle back motor dies(low rpm). Or I could start in forward gear with mid throttle and it would run just fine. I recleaned the carb, but am suspecting my needle needs replacing since I messed up cleaning the needle. My question is why does the replacement kit comes in a kit to replace 2 carbs when I only have 1 carb. Basically, I only need the needle and seat but would probably have to buy the entire kit. Any ideas/suggestions???

 

[John_S]

Re: Nissan NS40C

"My question is why does the replacement kit comes in a kit to replace 2 carbs when I only have 1 carb."

Huh? Not in the last one I received. I suspect either they sent you kits for a different engine, or mistakenly sent you two for the price of one.

"Basically, I only need the needle and seat but would probably have to buy the entire kit."

Thats true with just about all carb kits. It is usually not worth buying the piece parts. Harder to find too.

 

[TOHATSU GURU]

Re: Nissan NS40C

Sounds like afternarket junk to me.

 

[ventureman]

Re: Nissan NS40C

First of all, guru is correct. I ordered Sierra carb kit, made in Taiwan. After a little research, I found I could have ordered nissan (needle and seat only) for a lot less. Anyway, took motor out again today, still having the same problem.
Have to choke to start but die immediately. Mid range to wot is smooth. Not sure if my float is properly seated. What is the function of the float??? I think it open and close the needle. At idle, should the float be open or close? I am trying to understand the mechanics of the carburetor so that I can fix my problem. Primer bulb stayed hard all the time, so I think I can rule out the fuel pump. I have a diaphram (ordered to save on shipping with carb kit), but realized I need 2 for the fuel pump. I set my idle mixture at 1 3/4 turn. Lower and higher makes no difference. As for the pee hole, it is now working. It was clogged. Tried blowing with compressed air but that didn't do it, so I run weedeater line thru it, and is now peeing strong. I had always thought it was a thru exhaust water discharge. Thanks everyone. Still need your 2 cents on my idle problem.

 

[TOHATSU GURU]

Re: Nissan NS40C

Set the float by turning the carb upside and down and adjusting it until it is level. Your service manual, I'm sure you have one, has the answers to all your questions.