4 HP Yamaha only runs with choke pulled.....

[Norseman]

So I bought this motor new 3 years ago. Low hours and well maintained.
I use fuel stabilizer and try to run in once a month in a tank. This time I may have been over by
a few weeks.
Tried to run it in a tank yesterday and could not get it started.
Tried again today and finally got it going after 20 to 30 pulls. Then realized it only ran with the
choke know pulled. Every time I tried to push the knob in, the engine tried to die...
Got it warmed up and it would run rough and sputter at full throttle with the choke pushed in.
Pulling the choke back out got it running better.

Sooo, what is the problem? A clogged jet? Bad fuel.? (The fuel is from May this year, but the engine with internal
tank has been stored outside in 90 degree heat)

Any ideas...?

 

[emoney]

Re: 4 HP Yamaha only runs with choke pulled.....

Time to clean the carbs I think. Fuel stabilizer doesn't guarantee that today's fuel will be "debris free", it only helps. It's an easy enough job and if it's been 3 years, it's time.

 

[Norseman]

Re: 4 HP Yamaha only runs with choke pulled.....

Ah, good idea.
Is there "kits" for that kind of job?

Guess I could search right here at iboats...

Thx

 

[Norseman]

Re: 4 HP Yamaha only runs with choke pulled.....

Yamaha Outboard Carburetor Kits






There are no results for this search. Please correct search values or generalize your search.

Guess not....:facepalm:

4 HP and 2009 did not produce the desired result..Will try a broader search and Google and or ebay..

 

[Capt Ken]

Re: 4 HP Yamaha only runs with choke pulled.....

Remove the carb and clean. The o-rings should be reusable and if you are careful with the gaskets, they should be good alsol

 

[Norseman]

Re: 4 HP Yamaha only runs with choke pulled.....

Hmm, okay.
I hate to tear into a brand new engine without having a gasket kit ready, but whatever it takes...
If some jets are fouled up, I need air, or does carb cleaner do the same thing..?

 

[99yam40]

Re: 4 HP Yamaha only runs with choke pulled.....

use both
cleaner will help loosen and then blow out with compressed air

 

[emoney]

Re: 4 HP Yamaha only runs with choke pulled.....

It being only 3 years old, and as long as you're careful and take your time, you'll be ok reusing what's in there. Handy to have a camera by your side and a notepad for keeping track of what goes where. The key is to be thorough, somewhat anal, about cleaning each passage and port. Great little motors but they don't like dirt.

 

[Norseman]

Re: 4 HP Yamaha only runs with choke pulled.....

Handy to have a camera by your side and a notepad for keeping track of what goes where.

Yeah, good idea, thanks.

 

[Norseman]

Re: 4 HP Yamaha only runs with choke pulled.....

Well I got the problem solved and if anybody else has the same symptoms, here is the gouge:

Part Nr. 5 and Nr. 10 was glogged and gummed up with some hard black substance:
Used needles, brushes, carb cleaner and compressed air and finally got everything clean. Now the
little motor runs like a swiss watch and purrs on idle like a kitten.

Reference the numbers above, here is a parts diagram:




Nr. 5 is not a rubber cap, but rather a bronze nut/valve.

After seeing the innards of the carb, it was surprising the engine ran at all.
Not sure what caused the problem, but once or twice I have used a gas can that held 2-stroke fuel previously, hence
some oil residue could be present..(Don't think it did the carb in, bit who knows?)
The fules lines and fuel filter was clean, so dirty fuel is not suspect, more some chemical reaction in the carb...(?)

google F4MSH if the diagram does not show..