Pro 50 surge , poor acceleration

[Freaky1974]

I’ve a ‘97 pro 50
on occasion, the motor will sputter at a high speed - it idles rough on occasion
around 3500-till about 4200 it surges
seems to be a good amount of fuel in the water when it runs.

i understand , only the top carb has idle jets ?
the other carbs - no difference when turning the mixture screws.

once, after a high speed run, and allowing the motor to idle, it stalled- the ball was soft

ive checked spark - no problems
timing is set correctly and it’s advancing.
new fuel lines and filters.
the carbs have been apart twice - spotless clean

any ideas ?

[walleye1]

Clean the carbs in an ultrasonic cleaner and replace all the needle and seats.

[Freaky1974]

That’s what was done

[walleye1]

Check the fuel pump, if it checks good go back through the carbs. Or you can bring it to me.

[Freaky1974]

Check fuel pump ?
how ?

[walleye1]

Un bolt it from the block and pump the primer bulb if it leakes replace it.

[walleye1]

If you have a sm there is a procedure with a mityvac vacuum pump to check it.

[dark_star]

Check the bulb and hose and make sure the correct end is connected to the motor.
arrow on the bulb points to the motor

[boscoe99]

Each carburetor has a main jet and an idle jet. What Yamaha calls a pilot jet.

If the carburetors have not all been fully disassembled, with three main jets and three idle jets being cleaned and verified to not have any debris within the jet orifice, they may not been cleaned. Same thing with the main jet needle.

My sad experience indicated to me that if the carburetors are not completely taken apart and cleaned in a heated ultrasonic cleaner, one might be wasting their time. All of the passageways and orifices need to be verified to be working properly. Rod them out and spray water or cleaner through them as a visual indication.

[99yam40]

there is no P50 listed for 97 or 98, but there is for 96
are you sure about what motor you have.
also if the carbs are cleaned and then trash hiding in the lines or pump hit the carbs you get to clean them again.

I am guessing that motor whatever it is, probably a prime start, so make sure all of its passages and components function as they should, if it does not shut off the extra fuel when warmed up it will be running too rich

[rodbolt17]

dunno,in the past 42 yrs of doing this I have never used an ultrasound cleaner.
I have probably done as many carbs as most any two posters.
I was about 17 when I went to a Rochester class on the monojet,2bbl and Q-jet.
that 50 each carb has a pilot fuel jet,a main jet,a pilot air orifice and a mixture screw.
unlike many carbs you cannot really change the A/F mix. you can allow MORE or LESS of the mix from the orifice and the pilot jet.
there is a rubber plug that does not come with the carb kit that fits over the pilot air jet.
if it leaks or got left out that motor gets stupid.
all the fuel that motor burns comes through the main jet.
a torn lift pump diaphram will leave fuel on the water at idle.
a prime start device that fails to extend can.
the prime start fuel pump can fail and make it pig rich.
that is why you can manually override the prime start.

[boscoe99]

dunno,in the past 42 yrs of doing this I have never used an ultrasound cleaner.

Folks coming here more than likely have never done one carburetor.

They don't know, can't know, what you have learned in 42 years of working on motors on a daily basis.

Using an ultrasonic heated cleaner with a good cleaning solution will vastly increase the backyardigans chance of getting it done right. The first time. IMO.

Which is a reason why Yamaha recommends them to the mechanics that work at Yamaha dealerships. Many Yamaha mechanics in title are not much more than backyardigans in their early stages of working on Yams.

Recommendations are given to those that need them. Not to those that don't need them.

[rodbolt17]

back in the day an ultra sound machine was very expensive and we did not have the cwap fuels we have today.
we have found one of the few chemicals that clean the green goo from brass jets and bowls and needle seats is Yamha Combustion Chamber Cleaner.
following a soak in that I use CRC-06064 carb cleaner sometimes I may even use compressed air.
if the needles leak then I cut a q-tip in half. chuck one half in a drill.
place a dab of fine valve lapping compound in the seat bore and hit it with said q-tip.
this will clean the seat without altering the contor.
now ya really gotta clean a carb.
not the first rubber plug I ever saw left off the pilot air jet hole.
in fact it is funny to watch the look on a trainee's face when you slip a spare plug out of your box and place it on his work tray when he isn't looking, AFTER he has reassembled the carbs.
why that plug does not come with the kit? Beats me.
same as some kits with replacable seats do not include the seat to body oring.
but they all include spare bowl screws.

[pstephens46]

Folks coming here more than likely have never done one carburetor.

They don't know, can't know, what you have learned in 42 years of working on motors on a daily basis.

Using an ultrasonic heated cleaner with a good cleaning solution will vastly increase the backyardigans chance of getting it done right. The first time. IMO.

Which is a reason why Yamaha recommends them to the mechanics that work at Yamaha dealerships. Many Yamaha mechanics in title are not much more than backyardigans in their early stages of working on Yams.

Recommendations are given to those that need them. Not to those that don't need them.

Wish I had an ultrasonic cleaner right now. I have a grumpy clunking helm pump. Started clicking awhile back, now clunking. Motor ****s as you turn wheel. Would be nice to drop all the parts in for a bath. No boating today and 80 degrees.....

[Freaky1974]

Found the fuel pump gasket damaged at the pressure fitting
bolts holding the pump on the block were loose

could this cause the condition I have ?