really hard cold start

[medicineman]

I have purchased a 1987 yamaha 70 hp that sat for several years. I have cleaned carbs, put in new plugs, installed new fuel pump, cleaned fuel filter, and replaced water pump. It runs and idles great once i get it cranked, but can be a beast to get it going. To get it to crank, i set it with fast throttle all the way up and choke all way closed, it smokes quite a bit and sounds like it is running on two cylinders when it finally hits, then gradually over a minute or two smooths out and will idle perfectly. rIf i cut if off it will restart immediately. Let it sit an hour or two and have the same problem all over again.By the way, compression check shows 130, 130, 125 on cylinders. All suggestions appreciated!

[panasonic]

Do you have a manual for the engine? Does it run well after you get it going?

Please provide the engine data plate information so we know exactly what engine you have.

[rodbolt17]

watch the choke plates with the air box off. make sure all 3 close correctly.

[TownsendsFJR1300]

Do you have a manual for the engine? Does it run well after you get it going?

Please provide the engine data plate information so we know exactly what engine you have.

On the parts site here, there's only one engine with a carb pic.

As noted above, all three carbs have a simple choke plate for cold start up.


http://www.boats.net/parts/search/Ya...TOR/parts.html

[medicineman]

Do you have a manual for the engine? Does it run well after you get it going?

Please provide the engine data plate information so we know exactly what engine you have.

70 etlh is model. runs and idles perfect (at least on muffs as i have not installed it yet) once i get it going. i have removed both jets and needle valve assemblies and clean them and their holes out well. I thought i blew carburetor fluid thru all passages in carb body.......but it is possible i missed something i guess. I do have the factory manual.

[medicineman]

watch the choke plates with the air box off. make sure all 3 close correctly.

all three choke plates close completely. when i pulled them off to clean the carbs a couple of days ago all three bowls contained fuel----can't say whether they were full, but seemed quite a bit did dump out of them when i removed them. I am really wondering if i missed cleaning some passageway in carburetors----i am sure nozzles and jets were cleaned well.

[rodbolt17]

dude google some operational parts of a carb. the choke on that system bypasses most everything.now if the choke plates wont close AND stay closed when cranking no extra fuel for cold start is avalible and guess what? it wont start cold. have you tried starting it with the manual choke?

[99yam40]

I am thinking he may be flooding it due to all of the smoke at start up.
needs some air as well as fuel to fire properly
have you tried checking spark to make sure all is good when it is not starting up.

spraying some fuel mix into the carb throats at a cold start to see if it will fire up might help determine if the problem is lack of enough fuel

[boscoe99]

If what you are doing is not working try something different. For example, don't raise the fast idle lever and see what happens. Maybe try the fast idle lever just half way up and see what happens.

Try applying the choke for only a moment when the motor is first cranked and then remove the choke and see what happens. You might stumbled upon a procedure that works.

I agree with 99yam. Sounds like it might be flooding out and not starting. The smoke, the motor not running well at first but then clearing up over time, sounds like an excessively rich condition at start up.

[JerEazy2]

my older carbed engines had almost a ritual required before they would start. Like my old Johnson was fuel bulb till hard, pump the throttle to WOT 3 times, Turn key for 7 seconds, tap choke twice while engine is turning, stop turning key key, pump the throttle again, Turn key with no choke and hold until start (normally was 3-5 seconds)

you just need to figure out the ritual.

[boscoe99]

my older carbed engines had almost a ritual required before they would start. Like my old Johnson was fuel bulb till hard, pump the throttle to WOT 3 times, Turn key for 7 seconds, tap choke twice while engine is turning, stop turning key key, pump the throttle again, Turn key with no choke and hold until start (normally was 3-5 seconds)

you just need to figure out the ritual.

Exactly. Find out what it is that the motor wants. Then give it to her.

[99yam40]

my older carbed engines had almost a ritual required before they would start. Like my old Johnson was fuel bulb till hard, pump the throttle to WOT 3 times, Turn key for 7 seconds, tap choke twice while engine is turning, stop turning key key, pump the throttle again, Turn key with no choke and hold until start (normally was 3-5 seconds)

you just need to figure out the ritual.

Pumping(moving) the throttle back and forth only helps if there is something in the system that will shoot extra fuel into the throat/intake (like an accelerator pump on older model carbed automobiles).
In my opinion doing it on an old 1987 70 2 stroke is not going to do much to add more fuel to a cold motor
and I am not sure if it helped on your old johnson, because I have no clue if it had anything to to dump more fuel either

[medicineman]

If what you are doing is not working try something different. For example, don't raise the fast idle lever and see what happens. Maybe try the fast idle lever just half way up and see what happens.

Try applying the choke for only a moment when the motor is first cranked and then remove the choke and see what happens. You might stumbled upon a procedure that works.

I agree with 99yam. Sounds like it might be flooding out and not starting. The smoke, the motor not running well at first but then clearing up over time, sounds like an excessively rich condition at start up.

I have tried many ways, but that is the only way i can seem to get it cranked. I am thinking of opening fuel screw about 1/4 turn on each carb as i have it set at the 1 5/8 turn manual calls for now. if that does not help i am wondering if i need to splurge for 3 carb kits as all i did was open these up and clean them. very basic design (about like a briggs and stratton) and besides a little residue looked good so i just cleaned and reassembled. Like i said earlier, unless i missed a passage in carb body, i feel i got the jets opened up fine.

[JerEazy2]

Pumping(moving) the throttle back and forth only helps if there is something in the system that will shoot extra fuel into the throat/intake (like an accelerator pump on older model carbed automobiles).
In my opinion doing it on an old 1987 70 2 stroke is not going to do much to add more fuel to a cold motor
and I am not sure if it helped on your old johnson, because I have no clue if it had anything to to dump more fuel either

You might be right - it may have done nothing. All i know is that (like the Fonz and a jukebox) if i did that, it started. If i didn't, it wouldn't.

We all know engines are more fickle than women. sometimes they just need some lovin.

[TownsendsFJR1300]

I have tried many ways, but that is the only way i can seem to get it cranked. I am thinking of opening fuel screw about 1/4 turn on each carb as i have it set at the 1 5/8 turn manual calls for now. if that does not help i am wondering if i need to splurge for 3 carb kits as all i did was open these up and clean them. very basic design (about like a briggs and stratton) and besides a little residue looked good so i just cleaned and reassembled. Like i said earlier, unless i missed a passage in carb body, i feel i got the jets opened up fine.

Did you pull the idle and HS jets for a visual?

Often, these jets have orifices that go sideways and simply looking thru one end won't cut it...

Each jet should be pulled, initially check to see if light can be seen thru it, then cleaned.

You'd be surprised how much varnish can build up in those very, very small holes..