Nissan 2005 6 HP 4 Stroke Surging and poor idle

[w2much]

Can not get this thing to idle correctly . Starts well. Sometimes the idle is way to high other times it will stall at the same throttle setting.Have to keep playing with the throttle to keep it running.If I screw in the idle stop screw it will idle fine then next start it will rev way to fast. Can I soak this carb? It has plastic choke and throttle plates?

 

[tommarvin]

Sounds like a dirty carb, I would start by cleaning it without taking it off the motor, Take the bowl off check the float switch,moves freely ? Most important,clean the idle jet for a smooth idle.Get the largest drill bit that will fit in the idle jet tube,gently clean it out. blow with compressed air if possible.There are a lot of little holes in idle jets. There's a high speed jet also, check that also,

 

[raczekp1]

its common in 4-6 hp 4 stroke Tohatsu/Mercury/Mariner/Nissan that when you start motor rpm are to high but after a couple seconds it just go down to propper idle.
but its no harm to clean the carb

 

[pvanv]

Clean the carb correctly. Do not use any drill bits anywhere near it.

 

[w2much]

Thank you for your replies. The slow jet and the main jet will not budge for me. I need to remove them both for proper cleaning and to get to the main nozzle. They obviously have been tried in the past as the screwdiver slots are disfigured and I am unable to turn them ccw for removal. I guess I will have to drill them out unless there are better suggestions. The idle surges even when engine is plenty warmed and it surges quite high.

 

[w2much]

Forgot to ask again about soaking the carb. It has plastic throttle and choke plates. How long can they be soaked without harming them?

 

[tommarvin]

Time to take the carb off, we spray PB blaster three times on everything seized and wait at least over night. IDK what cleaner is ok for soaking plastic, some plastic can be plenty strong, get the largest diameter wire,drill bit don't turn it just ream it out gently, tooth picks just clean all the little holes, blow with compressed air if possible.
Or should you try a spray carb cleaner first,spray it in the throat since it run, if it didn't run you have to take it off to clean it.

 

[w2much]

This is a 1 cylinder engine. What should the compression be.What low is acceptable. I came up with only 60 lbs

 

[pvanv]

Definitely sounds like you need a good carb cleaning. Yes, you want to pull the jets to get to the emulsion tube nozzle, but if you can't get them out due to prior screwdriver damage, that's a sign that the carb was abused. These carbs can be submerged in carb dip for 4 hours no problem; we then thoroughly blow them out with a whole can of generic carb spray. Often, there is some crud that cannot be removed with the jets and tube in, so you could try drilling (jets are available), but you may well end up with a new carb, since it's pretty easy to do damage when drilling. If ordering a carb, order the one for the 6A2, as it will have the best idle.

 

[pvanv]

The motor has a decompression feature to make starting easier, so 60 pounds is fine.

 

[Sea Rider]

Could apply an overdose of power tuner in every jet, slot, let soak for some time, to clean apply carb spray liberaly. If jet screwdriver slots are worn-out that carb has already had it. If you run carb dry after each outing will not need to clean/soak, mess with carb as will stay inwardly clean.

Happy Boating

 

[w2much]

Picked up this motor for a song. As long as the compression is ok I think it best to buy the new carb. They are priced very reasonably. There are two carbs listed for my motor which is a 1 cylinder 4 stroke 6HP NSF6B S 3r4-1 Serial # 001262XH Nissan I believe it is a 2005. There are two carbs listed for this motor under Tohatsu. Under the Tohatsu parts list for the NSF6B there is the 3R4A 3R4 03200 0 and the 3AUA 3AU 3200-0. For the 6HP NFS6A2 only the 3R4 03200-0 is listed. Which carb is the best carb for my motor? PVANV are you saying that the 3R4 03200 0 carb is preferred over the 3AU 3200-0.? What is the difference?

 

[pvanv]

The earlier carb was designed to an earlier EPA standard, and is less sensitive to minor variations in operating conditions. They usually idle better, and have better tip-in characteristics. The newer carb has leaner, narrower, longer passages, which, while producing slightly lower emissions, do not perform as well. The carb for the 6A2 is the better all-around choice, and is what people use to up the HP of any MFS 4 or 5, as well as the preferred replacement for the MFS6.

 

[w2much]

OK great.Is there another carb that will give more HP to my engine? Thank you for your reply.

 

[pvanv]

OK great.Is there another carb that will give more HP to my engine? Thank you for your reply.

Nope. The 6 is the big brother in the 4/5/6 family. The 8 is a 2-cylinder unit.

 

[w2much]

pvanv. Thank you . I am going to order a new carb and other parts today.Appreciate your replies.

 

[pvanv]

Glad it helped. I would suggest carb base gaskets (2) and a fuel filter might be on the list. Possible oil drain plug gaskets. maybe some non-epa fuel hose (sold in 1-meter lengths), and if you have the "new style" epa-rated fuel line clamps (flat metal type) get a few of the older-style stainless wire-type clamps -- much easier to get on and off, and they seal just fine. Don't try to pull the long carb mounting screws with a phillips screwdriver -- you'll mangle them. Use a 10 mm socket. If needed, pull the 3 screws (also 10 mm heads) to get the recoil out of your way.

Remember to always, religiously, run the carb out at the end of each and every day, unless you KNOW you will be running tomorrow. That will greatly reduce varnishing. Use non-synthetic 10w-30 FC-W oil... never a drop over full. Change the plug when dirty, even though it is still firing. Non-E gas if you can get it; stabilizer if you can't; dump it in the car after 30 days.

 

[w2much]

Got my package of goodies today. Replaced a few parts. New carb went on easily I was done and starting her up in ten minutes. No idle adjustment just pulled it and it ran perfect. In this case much easier to just bite the bullet and buy the new carb. Thanks for your help