Throwing fuel out exhaust

[Floatober]

Hey fellas. 90 Frankenstein been running great till 2 weeks ago. Last week started great at dock after not being started for a month. Got about 500 yards from dock and had to turn back due to extreme vibration. I tried to throttle through it but motor wouldn’t increase rpm under load. So I pulled her out and took her back home. Even though the tank is literally brand new and the gas was fresh, I rebuilt carbs to eliminate this option. They were clean, but still used a rebuild kit. So this evening I put on muffs, as neighbors were hanging their lights..and the yammy ran horribly. Started like a champ, idled at 1300 nicely for seconds the shut off. I’m pumped...start her back up easily and idle is choppy fighting to keep it running. So it’s smoking while doing this, no surprise there, but my prop was 2’ from my closed garage door. I notice it spitting fuel mixture onto the white door. A lot of it, along with tons of smoke for my neighbor...I could easily start it but not maintain idle. Increasing throttle didn’t increase rpm, but I could tell the choke was turning on and off by engaging it. So, what would you expect the problem was? Also brand new plugs...Appreciate it y’all

[boscoe99]

Ruptured fuel pump diaphragm would be my guess. Assuming it is a two stroke model.

[TownsendsFJR1300]

Plus 1 ^^^.

The spark plug/cylinder is takes it's pulses from should show it (the spark plug), being wet/ fouled...



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[rodbolt17]

dunno
is this a gas motor or electric?
not enough information.
my weedeater has a carb.
why is it so difficult to ID the motor when asking questions???????

[TownsendsFJR1300]

dunno
is this a gas motor or electric?
not enough information.
my weedeater has a carb.
why is it so difficult to ID the motor when asking questions???????

From an earlier thread:

"the mid section evidently is a late 80's the power head and lower unit are late 90's, according to local Yamaha guy."



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[rodbolt17]

does anyone realize how many motors of various brands I deal with everyday plus posting?
you expect me to look at old threads?
why not simply post what you have BEFORE asking the question.
it is that simple.
you wont walk into an auto store and ask for an alternator to fit a truck.

[Floatober]

Good point Rod, appreciate the reference Towns. It’s a Late 90’s powerhead and lower unit with a late 80’s middle. It’s a 90hp Yamaha 2 stroke. I’m gonna take the fuel pump apart now to look for a tear, I can’t believe the amount of oil this thing spit out! Appreciate the feedback.

[Floatober]

Update...I took all 3 carbs apart and reset the float angle. My Yamaha rebuild kit came with entirely plastic floats. I didn’t measure the depth but all 3 didn’t seat the needle entirely when I flipped the carburetor over. So I heated and bent the tab on the hinged side of the float. Now all 3 allow the needle to plug the jet entirely. This is all I did before taking it out for a test run. It ran great! No more spitting fuel or vibration and had full power. BUT now my idle is only at 500 rpm and dies easily when shifting from neutral to gear. What a headache this is when docking. So question how to adjust idle correctly and why is it so much lower than it was before...around 700rpm

[panasonic]

I don't why you would have to bend the float tabs to get the needle valves to shut completely. They are preset set from the factory....perhaps they are not the right ones for your carbs? Did you replace the float needles as well?


Never the less you have it done now. Did you link and sync the carbs after putting them back on? If so, you can turn up the idle with the idle screw on on the carb linkage.

[Floatober]

Yeah that’s what I thought but I confirmed the part with my supplier. Yes the needle valve is new. So the link n sync is on point I think and when I adjusted the idle screw on the water it didn’t seem to make a difference. I’m confused as to why the idle would have changed, any theories?

[TownsendsFJR1300]

It shouldn't have changed..

Advanced timing would raise the idle but you didn't mess with it..

The throttle shafts (all of them) ARE FULLY CLOSED?

There should be an adjustment between the throttle linkages. Perhaps one moved (or just the R&R of the carbs slop) and one throttle blade is NOT closed fully.

Loosen all the linkages and make sure ALL are fully closed (then linkages tightened) before adjusting the idle screw.


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[99yam40]

every time the carbs are put back on they need to be synced together. Hope you did that when reinstalling them. During the link and sync you adjust the RPMs with the idle speed screw. as far as why it changed ,maybe not all cylinders are fire properly at idle. Scott, how are you able to separate sentences with blank lines? even when I hit the space bar and install blank lines they go away when I post to the forum.

[99yam40]

That is what I have always done and still do, but when it posts it is all packed together. the space bar and enter show up as they should when typing, but slams back together when I post. strange things going on