2002 F50TLRA Main jets not the same?

[wesleyjames]

Good afternoon. I am working on a 2002 F50TLRA 50HP 4 stroke outboard. Original owner - carbs have never been messed with. I'm in the process of cleaning all the carbs. I noticed that all 4 carbs have different main jets. #1 carb = 124, #2 carb = 126, #3 carb = 116, and #4 carb = 114. The factory parts diagram does list these 4 main jets - but it does not specify which carb gets which main jet. Is this correct? Just making sure - I'm used to all the main jets being the same. Thanks for the help, Wes

[boscoe99]

hm. Based on this diagram..

https://www.yamahaonlineparts.com/oe...02/CARBURETOR/

..from top-to-bottom, the order is 124, 126, 116, 114. I've worked on the carbs for a 2001 F50TR, and they all looked the same to me. But I cleaned one at a time, so I didn't mix/match any of the jets between carbs.. so I can't be sure if they're all exactly the same.

Have you no sense of decency man?

[TownsendsFJR1300]

The parts list at BOAT.NET (the SPONSER HERE) shows the different jets available, period: https://www.boats.net/catalog/yamaha...lra/carburetor

How do the spark plugs look, pretty much the same?


I wouldn't think the jets would be different in the same engine (especially water cooled). Perhaps assembled on a late Friday...



As you noted, the main jet, part #17 is available in different sizes.

Unless you have a plug burning much different than another, fouling, etc, I'd leave them where they were..

[boscoe99]

Good afternoon. I am working on a 2002 F50TLRA 50HP 4 stroke outboard. Original owner - carbs have never been messed with. I'm in the process of cleaning all the carbs. I noticed that all 4 carbs have different main jets. #1 carb = 124, #2 carb = 126, #3 carb = 116, and #4 carb = 114. The factory parts diagram does list these 4 main jets - but it does not specify which carb gets which main jet. Is this correct? Just making sure - I'm used to all the main jets being the same. Thanks for the help, Wes

Here is what the factory parts catalog indicates. Straight from Yamaha. I added the circles and the arrows by the way.

[TownsendsFJR1300]

Curious, how do you know that order (4, 3, 1, 2) ?


(and part #17, not 18 should be highlighted )

[pstephens46]

Have you no sense of decency man?

Milennial.... oops Millennial

[boscoe99]

Curious, how do you know that order (4, 3, 1, 2) ?


(and part #17, not 18 should be highlighted )

Yes, I highlighted the wrong item number.

The order is 4, 3, 1, 2 because that is the way that Yamaha listed them in their parts catalog. Does Yamaha have it correct? Don't know.

I can only presume that during development they measured the air/fuel ratio and determined that the different carburetors required different main jets to get the air/fuel ratios the same.

[boscoe99]

unedited parts catalog.

[wesleyjames]

Thanks for all the responses. Spark plugs looked OK. Nothing stood out to me. I was just taken back by the different main jets on all each cylinder. The parts list I was looking at didn't list the cylinders next to the respective main jet. I was just ruling out that this engine wasn't assembled Friday before a holiday or something!

[boscoe99]

Did you notice that the float bowls all have a different part number and position as well? I hope so.

[TownsendsFJR1300]

unedited parts catalog.

Interesting!

It would certainly make things difficult for the layman doing all 4 at once...

[wesleyjames]

Here is what the factory parts catalog indicates. Straight from Yamaha. I added the circles and the arrows by the way.

Boscoe99 - can I ask you one more question? In another post you recommended bumping up the pilot jet from a 39 to a 42. You pointed out that the earlier carbs had the 42. Do you still recommend that? It looks like the early carbs were different from the later carbs. Being that the main jets are different sizes I'd don't want to bump up the pilot jet and mess with the main jet circuits.

[wesleyjames]

Did you notice that the float bowls all have a different part number and position as well? I hope so.

I did not notice that BUT I placed each carb is it's own disassembly bag that's numbered so I wouldn't get anything mixed up. Thanks for that heads up.

[nicky952]

I have a 2003 F50TLRB with the same carburetor setup.

i'm curios if you made and change or mod to the carb?

i notice 2003 F60 TLRB model. all 4 carburetor main jet size is #124.

has anyone ever swap them? or just install the F60 carburetor on to the F50? i think they are the same size?

[99yam40]

some a hole drilled the main jets on my C40 before I got ahold of it
took me over a year to figure out why I had a high speed miss.
main jets had the proper numbers in the proper places.
finally bought all new jets to fix.
do not try re-engineering things.
i