Fuel problem with 20hp four stroke.

[Johnmac78]

I have a yamaha 20hp four stroke.
It start no bother if you pump the throttle is takes it no problem
But if you twist it to max slowly it seems to run irratic.
It seems to be flossing itself
Allot of fuel in the water.
I have replaced the prime start.

Any ideas???

[TownsendsFJR1300]

Clean the carb(s).

Make sure all the old fuel is out..


What is flossing??

[DSmith1178]

I agree with the above...clean carb. When I bought my used F20 last year I had a very similar problem. Pull off the carb (its very easy), and clean the jets out. I used some very fine wire to clean out all the litle passages in the jets. Has ran perfect ever since. Also what I do is when your done for day run the motor out of gas by disconnecting fuel supply. When it dies, crack the drain plug on the carb to drain the bowl.

Dave

[robert graham]

If you're going to drain the carb float bowl then no real need to disconnect fuel hose "and run the fuel out".....I drain my carbs several times per year just to remove any water or debris that can/will accumulate there....it's an easy 5 minute job that is great preventive maintenance....

[TownsendsFJR1300]

If you're going to drain the carb float bowl then no real need to disconnect fuel hose "and run the fuel out".....I drain my carbs several times per year just to remove any water or debris that can/will accumulate there....it's an easy 5 minute job that is great preventive maintenance....

Its a little less fuel to catch (nothing in the lines, the bowls aren't completely full).

Glad to see someone doing this!!!

On my generator, chipper / shredder (any machine W/O a bowl drain screw and NOT used often), I remove the bowl (after running dry) or loosen almost to falling off and give a spritz of air to blow out the little bit of remainder. I then give a shot of say WD40 or spray penetrating oil just for overkill... Some Seafoam thru the spark plug hole, spin over, and park at TDC (to keep moisture out).

[chummy70]

Flossing is when you clean in between teeth... Flooding is when your motor runs like crap...

[TownsendsFJR1300]

Flossing is when you clean in between teeth... Flooding is when your motor runs like crap...

In his first post:

"It seems to be flossing itself"

How does an engine "floss" its teeth (and where are the teeth located)?

[Johnmac78]

It was a typo

Flooding it was meant to be.
Second time ultrasonic cleaning
Still the same.
Runs fine ticking over starts great but runs rough up the revs
It's like it's over fuelling.
Any thoughts.??

[99yam40]

Have you checked fuel pump?
Some motors can have a problem with
the pump leaking causing over rich problems, but I have no idea if that little 4 stroke would be one of them.

Have you inspected the plugs to see what they can tell you?

Just because you think it is flooding does not mean it is until you verify it.

[TownsendsFJR1300]

+1 ^^^ on the fuel pump leaking.

That would explain the extra fuel making it into the water too...

Tks for the clarification BTW..


Can you post a year and model #?