Shakes at idle; sneeze causes?

[cheetah chrome]

2002 150 TXRA

I popped my carbs back on yesterday and I am getting a random (what I believe to be) sneeze about one every 3-5 mins while running on the hose. Motor, to me, appears to shake more than I think it should at idle. Everything there tells me idle is lean but read on. And, I may be biased here because I am comparing it to my brother inlaws same vintage SWS2 150 that idles as smooth as can be.

So, here's the conditions:

Carbs are spotless. They were perfectly clean when I pulled them from the previous rebuild last year. I even cleaned the espresso machine at the same time and steam cleaned all passages w/ 1400watts of high pressure steam (shhh don't tell the wife). Special attention paid to the idle circuit, all jets I can see light through are clean when inspecting w a jewelers loop.

Fully link/sync per manual..then checked and rechecked. Pilot screws are perfect/not deformed in anyway, backed off from lightly seated exactly 1 1/4 turns.

For fuel delivery tank professional cleaned last year and all new fuel lines up to the carbs w double ties or clamps at every joint. Pumps are new. Only ethanol free gas since w/ ring free and stability red. Gas in tank looks perfect. Set boat w one corner down overnight and siphoned out lowest point in the am...no water or trash. Emptied separator no water or trash. Pumped gas through the system just prior to hooking up the carbs to purge and junk that might still be in there...found nothing.

Tried idling w gas cap off to check the vent no difference.

So what to test next?

I have (2) videos of what I am calling the offending sneeze if someone knows how to post a .mov.

[99yam40]

How was the idle last year after they were so called professionally done?
Sounds like a lean sneeze , are you sure 1 1/4 turns out is the correct setting for all of the carbs?

[cheetah chrome]

1 1/4 turns I am taking out of the FSM. I checked my Clymer too, it also states the same. The only thing professionally done was the tank cleaning, I did the previous rebuild on the carbs (I ultrasonic ally cleaned the bodies that time). This time through I didn't find really anything clogging but did an OCD level clean on them again. The only delta this time was I did set my float hieghts w the bowl gasket in. I seem to remember the idle being smoother...well atleast less shaky but maybe mistaken. I stopped by my parts counter today and showed the guy the videos and his opinion was I am chasing nothing. I just don't like the idea of lean anything in the world of 2 strokes. Again this sneeze is one every few minutes not like an obvious carb issue/sneezy motor that sneezes almost every time the lean cylinder fires.

Still open for ideas of what to test. I could trim the pilot screws out an 1/8 turn more to add a lil more mix to the party. I'd prefer to do that as a last option to not mask an issue.

[boscoe99]

-------------

[TownsendsFJR1300]

^^^, turn the screws back in to one turn out and richen up the mix...

[cheetah chrome]

I'm looking at lit-18616-02-01. 1 turn out crosses with the premix models. My model TXRA is oil injected.

[boscoe99]

---------------

[rodbolt17]

not gonna beat the A/F mix anymore.
my name is riply, belive your own pictures or not.
lean sneeze occasionally ON the FLUSHER is rather normal, I don't like it but submerge the gearcase and add some ex back pressure and see what happens.

yep most the manuals say to set the floats with the carb inverted gasket off.
trust me, do it carb inverted gasket ON.
did I mention gasket ON as in in PLACE.

comes down to a pilot air jet, a pilot fuel jet and that's it.
you can allow more or less with the "throttling screw" but you cant change the ratio.
not all carbs use this design,your 150 happens to use it.
don't compare an old tillotson off an elgine or a techumseh that hasn't been made since my granddad was a kid.

[cheetah chrome]

So am I.

Here is a snippet from my copy of 02-01. Also a section from the tune up manual

I read it as you are crossing incorrectly with my motor. The TXRA crosses w/ S150TR for US and Can (150FETO). The A, L, and Cs are premixers. Believe me I'm perfectly fine w finding the mistake I made so I appreciate the feedback.

[boscoe99]

------------

[boscoe99]

--------------

[TownsendsFJR1300]

Re-reading after Rodbolts post about NOT being in the water, the water back pressure DOES make a difference.

My F150, I can make / have a slight hesitation (accelerating just right) on the muffs. In the water, can't/won't happen.

If its not sneezing in the water and running good, I suspect your wasting your time for a non-issue..

[throrope]

Your sneeze reminded me of a YouTube video diagnosing a failure on a rebuilt 90 tlr power head.

Seems the orangutans that performed the rebuild among other misdeeds never installed the O-ring between a carburetor and power head leaving a big vacuum leak with consequential inadequate lubrication.

Not saying you did the same, but I've done worse.

[TownsendsFJR1300]

Your sneeze reminded me of a YouTube video diagnosing a failure on a rebuilt 90 tlr power head.

Seems the orangutans that performed the rebuild among other misdeeds never installed the O-ring between a carburetor and power head leaving a big vacuum leak with consequential inadequate lubrication.

Just curious, with that vacuum leak, ( ^^^ ), did the idle rise a bunch?

[99yam40]

With respect to setting the float height, the further away the float is from the surface of the carburetor the leaner the motor will run at idle. The level of the fuel in the bowl will be lower than it will be if the float is set higher.

When you measure the float drop from the gasket, and not the body of the carburetor, guess what? You are moving the float further. The motor will run leaner at idle.

I do not understand how this can be true.
A small adjustment in float height ( not drop) should not make that much of a difference.
Yamaha says could cause it to run lean,
But they may be saying a major difference from spec it might at high speed if not enough fuel is in the bowl. But a couple of thousandths should not make that much difference at idle