[help]rough idle , dies -1988 40hp 2 stroke

[midskargard]

hello everyone , this is my first post .


i have a 1988 Yamaha 40 2 stroke 3 cylinder Autolube
last year it ran good , but. not 100% !

Started it up 1 week ago and it takes 3 tries almost every time to start.
once started it idles VERY rough . a low idle and then suddenly a higher idle and then a low idle , then "click" , "pop" and it dies . all of this happens in about 10-13 seconds from starting -
the motor does this religiously just after being started .

ive gauged the new spark plugs . new impeller and gaskets , new gas in a new tank.charged the battery and was all ready to go when the motor wasnt .

im not a mechanic .
but i have been trying to educate myself .
i tried un-plugging spark plug wire 1 and starting the motor .
it idles rough , and it's a click , pop and die .
the same thing with spark plug wire 2 un-plugged ( 1 & 3 connected ) -
when i unplug wire 3 ( with 1 & 2 connected ) it idles rough , but not as rough and doesnt die .
a bad coil ?
im positive the carbs should be cleaned out , but. what other things should be looking at , or considering . im heading up to the marina a few clicks from here to talk to a mechanic in the morning .
but i was hoping for some help from the Yamaha pro's here on the forums .
thanks for any help advice before hand
Cheers

[99yam40]

It is always a good idea to test compression, spark, and timing on a motor just to make sure it is all good to start out with.

Checking Fuel pump is something on the fuel system you did not mention looking at yet. How old is it?

Clean the carbs and set as service manual calls for (Link and sync) every time the carbs are reinstalled.
The bottom carb usually ends up as the one with the most residue after fuel evaporates out of the bowls.
You are describing a lean sneeze caused by the pilot jet/passages plugging.

It is never a good idea to keep running a motor that is not running correctly. if running lean it will toast a piston

[TownsendsFJR1300]

+1 ^^^ re the carbs.

Thats a small engine and it doesn't take much to clog up the jets, especially the idle jets.

Make sure you actually pull them out, just don't look thru one end. Many of them have holes PERPENDICULAR (VERY SMALL, BTW) that you cannot see unless pulled out.

If you don't have a shop manual, it would be well worth your investment. Bringing up the parts fisch above (under purchase Yamaha parts) will give you a break down of where the jets are, etc...

I would strongly recommend, once fixed, a fuel stabilizer, even if you run it dry. A little bit of fuel will ALWAYS remain in the bowl and it usually clogs those jets... Yamaha's "RingFree" is an excellent fuel system cleaner (but isn't a stabilizer). Yamaha does make a separate fuel stabilizer.

Go slow, one carb at a time, find those jets and get them spotless.

Any fuel filters you find, clean or replace as well...

[midskargard]

HI .
i thank you both for the input and advice .

I managed to get to Marina this morning and talk with the head mechanic and explained the situation with the motor . the mechanic basically said the same things the two of you said . almost positive from my description its a carb related issue .
as i stated before . im not a spark & fuel mechanic ..
after talking with the machnaic
i drove back home thinking about the boatmotor and was told by the mechanic if i wasnt able to get the boat to him today its would be a few weeks before they could troubleshoot the motor .
in a desperate push . i drove back home , started up the boat and and it didnt die . amazingly i made it to the marina without a cough , sputter , at around ½ throttle all the way . it's a 30 min boat ride .
the boat is now in their hands and ill have a report back from them in a few days .
would it be ok if i posted what the result diagnosis is here , for other users ?

thanks again
CHeers from Sweden !
/MID Skärgård

[TownsendsFJR1300]

HI .
i thank you both for the input and advice .

I managed to get to Marina this morning and talk with the head mechanic and explained the situation with the motor . the mechanic basically said the same things the two of you said . almost positive from my description its a carb related issue .
as i stated before . im not a spark & fuel mechanic ..
after talking with the machnaic
i drove back home thinking about the boatmotor and was told by the mechanic if i wasnt able to get the boat to him today its would be a few weeks before they could troubleshoot the motor .
in a desperate push . i drove back home , started up the boat and and it didnt die . amazingly i made it to the marina without a cough , sputter , at around ½ throttle all the way . it's a 30 min boat ride .
the boat is now in their hands and ill have a report back from them in a few days .
would it be ok if i posted what the result diagnosis is here , for other users ?

thanks again
CHeers from Sweden !
/MID Skärgård

Yes, PLEASE post your fix. Most of the time we DON'T hear the results but personally, I would.

Just as a side note, if that motor ran that far, a good full dose of Ring Free, (now that it can get thru the carb) may have very well solved your issue. Also, as it ran that far, its likely not as clogged or you pushed some goo thru and the engine is now geting more fuel.

[midskargard]

@TownsendsFJR1300

HI again .
well this happened a lot quicker than i anticipated . the mechanic and i hit it off as he is a cyclist as well , so just after i left he put one of his best guys on the job.
it wasnt more than 2½ hours later i received a call from the mechanic . i was prepared for the worst . but what i received was good news . they cleaned the carbs and adjusted them and now he said its running like a clock .

so the bottom line is , clean and adjust the carbs .

on the other part . the mechanic said that the stering cable ( not sure whats its called in English ) is dead . so they will replace that on monday for me . for now i am on my way to take the boat home and and pike fish a couple spots on the way .
thanks again everyone for answering my question and for the prompt replies .
this documentation online hopefully helps someone else .

by the way : What is Ring Free
Cheers
/Mid Skärgård

i hope its ok to post the marinas info below ?if not please let me know and i'll remove it

a special thanks to Dyviks varv & Marina here in Roslagen Sweden

[TownsendsFJR1300]

"Ring Free" is a Yamaha product (if your marina is a Yamaha shop, they should have it or be able to get it) for cleaning the fuel system and top end of the engine. I run it 100% of the time in my boat and have NEVER had an ethonol issue. I do run Non-ethonol fuel for the last 2.5 years.

IMO, well worth the investment, much cheaper than paying someone to clean your carbs and NO down time.

Some folks will run their carbs dry after use however, UNLESS you pull the float bowl drains, there is ALWAYS going to be a little bit of fuel left in there. As the fuel evaporates, it varnishes up the innerds.


HIGHLY RECOMMENDED, (even Rodbolt uses it)...

Yamaha Ring Free Fuel Additive

[midskargard]

.. i actually googled it . and it seems to be a good product . those who use it are well impressed .
unfortunately the nearest marina ( Dyvik varv ) are Mercury & Suzuki re-sellers. so no yamaha gear . Ill try a bit south from me , there are Yamaha shops and im positive they have this product !

again , a bit thanks for all the tips and replies .
All the best .
/MID Skärgård !

[kingfish56]

'88 40hp .. last 3 times out, it runs flawlessly at higher rpm's, but when I shut it off and restart it, it won't run but a little past idle. It sounds like it's bogging starving for gas, but I'll hit the choke and it bogges it down so I dont think its not a fuel problem. It's not overheating, but being warmed up could be a factor. All the coils seem to be firing.....it almost seems like a timing thing. When I first go out, I can run it forever no problem...I have to shut it off and restart it before it malfunctions...thats the pattern...any ideas?

[TownsendsFJR1300]

Sounds like the idle jets (the smallest) may be clogged. Has the boat sat for awhile W/O a fuel stabilizer?

No other recent work, correct?

I'd at least drain the carbs, catch what comes out (looking for any crap/water) using the drain plug on the bottom of each bowl..



BTW, it's easier for us if you start a new thread. Keeps folks from getting engines(in the thread) mixed up-un-needed confusion.

[kingfish56]

Thanks for your input Scott...boat did sit...replaced fuel tank......yep, I went through carbs...dipped them when I puchased the boat, then again when performance started heading south.....their clean..cleaned fuel filter...I'll run it on muffs and check things out again this weekend and hope for the best...oh yea..my bad...I'm new here and couldnt figure out how to start a new thread...I gots to work on that too.

[walleye1]

Top left corner, new topic.

[TownsendsFJR1300]

Thanks for the additional information.

Dipping usually works good BUT those little orifices in the jets, as stated earlier do clog up with old fuel.

They (jets) HAVE TO COME OUT and be inspected after cleaning..

If you can't see light thru them, it ain't clean, don't count and you get to do a "do over"..


Pic of a badly varnished carb on a small machine I repaired:



And after sonic cleaning: