Nissan NS 70A won't idle in neutral

[Fishemup]

I have a NS70A nissan that will not idle .It stalls every time I stop and put the shifter into neutral.It will run if I put it it start up by moving the shift lever forward out of gear.It also spitters at slow speeds or when I am trolling .Can air leakage from bad fuel lines or lines on the carbs cause this?.
Could this be electrical I noticed that at 3000 rmp I was charging 14-15 volts?

 

[rogerwa]

Re: Nissan NS 70A won't idle in neutral

I would start with a good carb cleaning, link and synch. You need to follow the procedure in the factory manual to get it right. To keep it running temporarily you many be able to increase the idle speed by adjusting the screw on the top of the carb stack that will open all three carb throats at the same time . Probably a bad description but inpsect the carbs and you should find it.

Your low speed circuit, which has really small passages may be clogged.

 

[Fishemup]

Re: Nissan NS 70A won't idle in neutral

Thanks for getting back.

I have the green manual .It is a little vage in how to do do things .

Should I remove the carbs from the block or can I clean them still installed ?

Can the drain screw on the side of the carb help with cleaning ?

I noticed a little gas under the bottom of the lower bowl .I put a paper towel between them to see if there was any leaks.

Could this be caused when the engine is lifted for travel then put back down?

Where do I find the low speed circuit?

 

[James R]

Re: Nissan NS 70A won't idle in neutral

A good manual will save you time and money. The carbs must be removed and stripped. Parts and jets must be soaked to soften deposits, I recommend Gunk Parts and Carb cleaner. It comes in a gallon can with a little basket for small parts. Don't use spray cleaners as they can damage parts especially plastics and sealants.
Follow the instructions on the can.
Use new carb kits to rebuild.
Before doing all this it is a good idea to do a compression test and a spark test to ensure that all is well with these.
Your symptom is typical of one or more cylinders not working.
I forgot to ask if this has just now manifested itself or is there some history.

 

[Fishemup]

Re: Nissan NS 70A won't idle in neutral

Hi This seemed to come on when I changed 2 stroke oil and fuel filter .

I have the service manual that came with the boat ,is there a better on to use ?

Where can I get a carb kit .

I saw a small leak on the gas line on the side that conects the 2 carbs.

Would a air leak cause this problem?

 

[TOHATSU GURU]

Re: Nissan NS 70A won't idle in neutral

Parts are no longer available for that model engine and yes, an air leak will cause a problem like that.

 

[Fishemup]

Re: Nissan NS 70A won't idle in neutral

checked compression it was 148 psi in both upper and lower cylinders

ckeaned carbs .blew them out with compressed air

re installed them and it fired up

I have one question the needle valve on the side with the spring on it .

is there a setting that I should start at .I backed them out and they both had 9.5 turns .

what does this valve do ?

is it a idle or lean /rich ?

is this a fine tune valve?

thanks for the help

 

[pvanv]

Re: Nissan NS 70A won't idle in neutral

You set the pilot screws to about 1-3/4 turns out for initial start. Then you need to do a link and sync. That is all detailed in the Factory service manual. But beware that your model is obsolete, and parts are very rare to NLA.

 

[Fishemup]

Re: Nissan NS 70A won't idle in neutral

this may sound silly but what is link and sync ?

Is this where the Green service manual talks about extending the cables open and closed ?

it doesn't talk about that needle valve.

Any help would be great or a link to a web site.

 

[pvanv]

Re: Nissan NS 70A won't idle in neutral

this may sound silly but what is link and sync ?

Is this where the Green service manual talks about extending the cables open and closed ?

it doesn't talk about that needle valve.

Any help would be great or a link to a web site.

You need a better Factory service manual. Adjusting ignition/carb sync is fairly straightforward, as is adjusting the carbs. But beware that your model is obsolete, and parts are very rare to NLA.

 

[James R]

Re: Nissan NS 70A won't idle in neutral

Motors need to be adjusted so that the throttles open in sync with the ignition timing advance. I don't have a manual for your motor but you will find the procedure there. This is link and sync. One thing you can set is the adjustment to ensure that all throttles are closed fully when in idle. To do any adjustments disconnect the throttle remote cable.
The pilot screws or idle jet screws, the ones with the springs, should be initially set as stated. Once the motor is running it must reach working temperature and then adjust the idle jet screws in or out, one at a time, in 1/8 turn increments to achieve the best idle. Make an adjustment and allow a few minutes for the motor to adapt to the new setting before adjusting further. There may be a small spring tensioned screw on one of the carbs which sits on a stop in the fully closed position. Adjust this screw to set an idle you can start with then as you adjust the idle jet screws back this screw out to get to the lowest sustainable idle and continue to adjust the idle jets until smooth running or as near as you can get. Once achieved you can adjust the throttle stop screw to bring the RPM up to 850-950 with the prop engaged in the water or a little more without the prop engaged and in the water. This is to prevent stalling when engaging the prop in the water.
Best I can tell you flying blind. so to speak.

 

[Fishemup]

Re: Nissan NS 70A won't idle in neutral

Hi did what you stated and it idels good,but when i troll for a while and then start to move to a diferent location the motor bogs down and caughs then it pickes up and runs great.
I have pulled the plugs and the top plug looks new but the bottom one has carbon on it and is
brown color .
I went to the dealer and was told i have the wrong plugs installed .He told me I need NGK BPHS-10 not BHS-10 and the gap should be 38 not 40 as it says on the sticker in side the motor.
Is there a carb adjustment I may have missed

 

[pvanv]

Re: Nissan NS 70A won't idle in neutral

That dealer is mistaken. The P plugs have a projected tip, which is not what the motor was designed to use. Likewise, the correct gap is 1mm, which is roughly a tight 0.040", so 0.038" is OK, but will foul faster. You want B8HS or BR8HS. the -10 means absolutely nothing except that NGK made the plugs to run at 1.0 mm gap.

Did you ever do a complete disassembly and 4-hour soak (in real carb dip) of the carbs. If not, you are masking a varnishing problem. Start with the basics.

 

[James R]

Re: Nissan NS 70A won't idle in neutral

pvavv is somewhat correct about soaking the carbs. Four hours is a bit long. One hour and move the carbs around in the cleaner to get the stuff into the tiny bores. Dont use spray cleaner as that and does do damage. Use Gunk Parts and Carb cleaner Kit. It comes as a gallon with a small parts container, It will soften and remove deposits. Follow the instructions on the can.
Sounds like the idle jets are not quite set good. The transition is not good from the idle to the main jets, Try screwing them out 1/8 of a turn.

 

[Fishemup]

Re: Nissan NS 70A won't idle in neutral

Soaked over night

Do the idel screws (ones with springs) have to be in the same position mean up and down or can they be at different angles?

I have them both set at about 1 1/6 turns up and down ?

I had a hard time getting it to idel smoothly should I do them seperatly or together

When I tightned them (snug) the screws didnt line up the same does this matter?

 

[pvanv]

Re: Nissan NS 70A won't idle in neutral

The slots do not necessarily line up. Start at about 1-1/2 turns out initially. Try to adjust them equally.