1999 Yamaha 4 stroke F50TLRX running rich

[ChuckB1954]

Greetings! I just found this forum and am a new member

I recently purchased the subject motor. It seems to start and run normally out of gear, but after running it under a load, the plugs become black and sooty.
It seems the linkage to the choke butterflies are activated any time I move the throttle. The only thing that linkage is connected to is the throttle linkage.
Seems like there is nothing keeping the choke from opening and closing on it's own.
I noticed when looking at the parts diagram that two solenoids are missing. Would these missing solenoids cause my engine to run rich by allowing the choke to open and close on it's own??

Picture of my engine with the empty solenoid bracket shown in the center of the picture. Also solenoids in question. #9 and #36 shown in the parts diagram.

[TownsendsFJR1300]

For everyone as well: https://www.boats.net/catalog/yamaha...arburetor-link

You SHOULD have Prime Start, for cold start up (enriches the mixture), part #9.

I believe, that part missing (missing) would cause a rich condition. Someone else will have to chime in to confirm..


Looking at your picture (not so clear), it appears you have choke butterfly linkages, is that correct???

It shouldn't per the parts site: https://www.boats.net/catalog/yamaha...lrx/carburetor

[boscoe99]

A 1999 F50TLRX uses both a prime start assembly (thermoheater) and choke plates. The thermoheater in this model is causing the choke plates to open or close. It does not work like other PrimeStart components on other models. During the start the solenoid is energized and this also causes the choke plates to close.

Two strokes can have PrimeStart. Carbureted, EFI or HPDI.

Four strokes can have PrimeStart. Carbureted, EFI or Direct Injection.

A PrimeStart is not a PrimeStart is not a PrimeStart. It is a Yamaha term coined for automatic fuel enrichment. There are many ways and components involved to automatically provide fuel enrichment if and when needed.

[boscoe99]

[boscoe99]

Greetings! I just found this forum and am a new member

I recently purchased the subject motor. It seems to start and run normally out of gear, but after running it under a load, the plugs become black and sooty.
It seems the linkage to the choke butterflies are activated any time I move the throttle. The only thing that linkage is connected to is the throttle linkage.
Seems like there is nothing keeping the choke from opening and closing on it's own.
I noticed when looking at the parts diagram that two solenoids are missing. Would these missing solenoids cause my engine to run rich by allowing the choke to open and close on it's own??

Picture of my engine with the empty solenoid bracket shown in the center of the picture. Also solenoids in question. #9 and #36 shown in the parts diagram.

Only one solenoid is used. Please help me understand how two are missing? Or are you saying that both the solenoid and the Prime Start thermoheater are not installed on the motor? #9 and #36 in your illustration?

[panasonic]

Picture worth a thousand words. I was scratching my head looking at the parts diagram and was just going to see if I could get the info from the sevice manual to see how that works.

I guess those choke plates are not spring loaded open? Or that may have been part of the choke system that was removed also.

From his description the choke plates must be only partially closed as he can run it for awhile before fouling the plugs up.

Chuck....you need those parts on the engine to make it run properly as designed

[boscoe99]

Joe, send me your email address again plz.

[TownsendsFJR1300]

Picture worth a thousand words. I was scratching my head looking at the parts diagram and was just going to see if I could get the info from the sevice manual to see how that works.

I guess those choke plates are not spring loaded open? Or that may have been part of the choke system that was removed also.

From his description the choke plates must be only partially closed as he can run it for awhile before fouling the plugs up.

Chuck....you need those parts on the engine to make it run properly as designed

Looks like the "solenoid coil works" has a large, pull spring below it.

With the direction of the fuel flow arrows, it appears the spring holds the choke butterflys open and the solenoid closes them when activated...

As noted, missing those parts, the choke butterfly can flop around, open and close at will...

[99yam40]

I would be asking the people that sold it to you where the rest of the parts are

[ChuckB1954]

Thanks for all the great info. I will address each post one at a time and provide some more pictures.

[ChuckB1954]

For everyone as well: https://www.boats.net/catalog/yamaha...arburetor-link

You SHOULD have Prime Start, for cold start up (enriches the mixture), part #9.

I believe, that part missing (missing) would cause a rich condition. Someone else will have to chime in to confirm..


Looking at your picture (not so clear), it appears you have choke butterfly linkages, is that correct???

It shouldn't per the parts site: https://www.boats.net/catalog/yamaha...lrx/carburetor

The poor picture was captured from a video I made of the engine running. It was too late to go outside and take a decent one.

Took a closer look just now.. I can see how the prime starter assy could make this engine run rich. Without it, the choke linkage is flapping in the breeze and closes any time you give it throttle. I held the linkage contact point that the prime starter pushes on and not only does it stabilize the linkage, the choke doesn't move when you give it throttle unless I backed off that contact point.


Prime starter contact point:




As far as the choke linkage, see my first post.. it is shown in that diagram. ( https://www.boats.net/catalog/yamaha...arburetor-link )
here is my linkage:

[ChuckB1954]

Only one solenoid is used. Please help me understand how two are missing? Or are you saying that both the solenoid and the Prime Start thermoheater are not installed on the motor? #9 and #36 in your illustration?

Thanks for the pictures and info!

Yes, both the solenoid and the Prime Start thermoheater are not installed on my motor.. I mistakenly identified the part. I assumed.. two wires.. must be some type of solenoid.

[ChuckB1954]

Chuck....you need those parts on the engine to make it run properly as designed

Yes sir I do. I simulated the prime starter just now and realize just how critical it is. It will be the easiest to replace. The solenoid will be a bit more difficult with all the small pieces.

[ChuckB1954]

Looks like the "solenoid coil works" has a large, pull spring below it.

With the direction of the fuel flow arrows, it appears the spring holds the choke butterflys open and the solenoid closes them when activated...

As noted, missing those parts, the choke butterfly can flop around, open and close at will...

I am pretty sure replacing those parts will solve my engine running rich issues, but we'll see.

When I first got the engine (came with the boat) I notice that I could work that choke linkage by a push of my finger.. no resistance. I'm sure it was flopping around.

[ChuckB1954]

I would be asking the people that sold it to you where the rest of the parts are

Those parts are long gone.. Not really complaining and don't mean to brag, but I only paid 1,500.00 for the whole set up shown in the picture.



20190518_102922small.JPG