Air adjustment screw: 1985 90hp ETLK

[ctmnsow32]

Hey just wondering if anyone knows the set point/adjustment level for the air adjustment screws on the carbs for a 1985 ETLK? How many turns out from zero should i have them set at?

Thanks for reading and any advice would be great.

[robert graham]

Somewhere in the range of 1-1/2 turns out from lightly seated...give or take

[Jason2tpa]

1-7/8 +/– 1/4

This will be your where you'll set screws prior to fine tuning. It's ok if the engine requires more or less even if out of spec. What's most important is how the engine runs (sounds), not how many turns in/out it takes to get there, speaking in general....So I've been taught. 1/2 or 3/4 turns more or less than spec, no biggie. 2-1/2 turns out of spec...somethings wrong with the air/fuel passages

[boscoe99]

There is no air adjustment screw on a 1985 90 HP Yamaha.

I suspect that you are referring to the idle mixture screw. Also known as a pilot screw. As Jason notes, it is 1 and 7/8ths turn outwards from being just lightly seated. Plus or minus 1/4 turn.

[ctmnsow32]

awesome, thanks guys

[Jason2tpa]

There is no air adjustment screw on a 1985 90 HP Yamaha.

Correct me where I'm wrong bossman...if the "adjustment" screw is located on the intake side of carb, it can be labeled "air adjustment screw". If this screw is located on manifold side of carb, it can be labeled "fuel adjustment screw". And despite where this screw is located, IF it's the only adjustable air or fuel screw, it's labeled pilot screw.

[ctmnsow32]

There is no air adjustment screw on a 1985 90 HP Yamaha.

I suspect that you are referring to the idle mixture screw. Also known as a pilot screw. As Jason notes, it is 1 and 7/8ths turn outwards from being just lightly seated. Plus or minus 1/4 turn.

So i just cleaned my carbs and put in new pilot jets ( they were all chewed up by someone who didn't know how to get them out). I also noticed my plugs a fouled pretty bad. I feel like I should reset the idle mixture screw to ensure it is correct. Is this a good idea and will this potentially help?

[boscoe99]

Correct me where I'm wrong bossman...if the "adjustment" screw is located on the intake side of carb, it can be labeled "air adjustment screw". If this screw is located on manifold side of carb, it can be labeled "fuel adjustment screw". And despite where this screw is located, IF it's the only adjustable air or fuel screw, it's labeled pilot screw.

I am not saying anyone is right or wrong. Yamaha has their own terminology for stuff and I like to use that for the sake of consistency. Mostly anyway.

All I know is that Yamaha calls it a pilot screw. It controls the amount of fuel (with some air mixed within to facilitate the flow of fuel) that is drawn into the carburetor. Turning the screw outwards opens a passageway and allows more fuel to flow. Turning the screw inwards does the opposite.

The air that is mixed within the fuel is metered by a fixed air jet. It is separate from the pilot screw aka idle mixture screw. It is called a pilot air jet by Yamaha.

I have read about other carburetors that have a screw to adjust the amount of air being allowed into the carburetor. The 90 HP two stroke model does not use that configuration.

[Jason2tpa]

There is no air adjustment screw on a 1985 90 HP Yamaha.

I suspect that you are referring to the idle mixture screw. Also known as a pilot screw. As Jason notes, it is 1 and 7/8ths turn outwards from being just lightly seated. Plus or minus 1/4 turn.

I am not saying anyone is right or wrong. Yamaha has their own terminology for stuff and I like to use that for the sake of consistency. Mostly anyway.

All I know is that Yamaha calls it a pilot screw. It controls the amount of fuel (with some air mixed within to facilitate the flow of fuel) that is drawn into the carburetor. Turning the screw outwards opens a passageway and allows more fuel to flow. Turning the screw inwards does the opposite.

The air that is mixed within the fuel is metered by a fixed air jet. It is separate from the pilot screw aka idle mixture screw. It is called a pilot air jet by Yamaha.

I have read about other carburetors that have a screw to adjust the amount of air being allowed into the carburetor. The 90 HP two stroke model does not use that configuration.

Oh no, I wasn't suggesting right or wrong. When the OP used the phrase air adjustment screw it made me think about the pilot screw, in that I believed the OP was interchanging these two name for the same screw. I was just confirming with you if my thought process was correct or needed correction. Somebody told me how you tell the difference btwn a fuel adjust screw and air adjust screw based on the screw location. It made sense to me, but I didn't know if in fact this is correct carb terminology.

[Jason2tpa]

There is no air adjustment screw on a 1985 90 HP Yamaha.

I suspect that you are referring to the idle mixture screw. Also known as a pilot screw. As Jason notes, it is 1 and 7/8ths turn outwards from being just lightly seated. Plus or minus 1/4 turn.

I am not saying anyone is right or wrong. Yamaha has their own terminology for stuff and I like to use that for the sake of consistency. Mostly anyway.

All I know is that Yamaha calls it a pilot screw. It controls the amount of fuel (with some air mixed within to facilitate the flow of fuel) that is drawn into the carburetor. Turning the screw outwards opens a passageway and allows more fuel to flow. Turning the screw inwards does the opposite.

The air that is mixed within the fuel is metered by a fixed air jet. It is separate from the pilot screw aka idle mixture screw. It is called a pilot air jet by Yamaha.

I have read about other carburetors that have a screw to adjust the amount of air being allowed into the carburetor. The 90 HP two stroke model does not use that configuration.

Oh no, I wasn't suggesting right or wrong. When the OP used the phrase air adjustment screw it made me think about the pilot screw, in that I believed the OP was interchanging these two name for the same screw. I was just confirming with you if my thought process was correct or needed correction. Somebody told me how you tell the difference btwn a fuel adjust screw and air adjust screw based on the screw location. It made sense to me, but I didn't know if in fact this is correct carb terminology.

[TownsendsFJR1300]

So i just cleaned my carbs and put in new pilot jets ( they were all chewed up by someone who didn't know how to get them out). I also noticed my plugs a fouled pretty bad. I feel like I should reset the idle mixture screw to ensure it is correct. Is this a good idea and will this potentially help?

Did you not remove the air screws with the carb cleaning? Should have..

Much varnish / crap in the system?

Can we assume you sync'ed the carb linkages once re-assembled to the engine-IMPORTANT!


Anyway, now that the carbs are hopefully clean, replace the plugs (they need it anyway) and simply adjust the "screws" to within range.

Fine tune as need be.

Keep an eye on the spark plugs after a couple of hours run time to make sure their burning properly.

As posted above, turning them in (clockwise) will LEAN out the idle mix.



.

[BQUICK]

If they are indeed AIR screws then turning in would richen (less air).

[boscoe99]

If they are indeed AIR screws then turning in would richen (less air).

They are not air screws. They are what Yamaha calls pilot screws. They are designed to control the amount of gasoline. Not the amount of air. The air jets are fixed orifices.

But you raise in interesting point about the effect of an air bleed screw. Within limits allowing less air to flow might cause the mix to richen. But, stop all of the air and the mixture might then turn lean. Very lean.

The purpose of allowing air to be bled into the system is to increase the amount of fuel that can flow. If the air bleed was allowed to be closed off completely the amount of fuel that would flow would be less, not more. Causing the motor to runner leaner than if air was allowed to be bled into the system.

Things are not always as they seem. Keeps life interesting.

[boscoe99]

Did you not remove the air screws with the carb cleaning? Should have..
.

What air screws?

[boscoe99]

Oh no, I wasn't suggesting right or wrong. When the OP used the phrase air adjustment screw it made me think about the pilot screw, in that I believed the OP was interchanging these two name for the same screw. I was just confirming with you if my thought process was correct or needed correction. Somebody told me how you tell the difference btwn a fuel adjust screw and air adjust screw based on the screw location. It made sense to me, but I didn't know if in fact this is correct carb terminology.

As we have discussed many many times there are many many different Yamaha models. There are just as many different carburetors being used as there are Yamaha models. Maybe more. People read about something on one particular Yamaha model or one particular carburetor and then come to the belief that all Yamaha models or all carburetors share the same features.

I suspect the OP read about an air adjustment screw that relates to a different carburetor. With an assumption being made that his carburetor has one. Which is why he used the term air adjustment screws. I was merely trying to set him and the record straight.

Kinda like the guy that reads about a choke on a carburetor needing to be adjusted. He then asks about a choke on his model Yamaha. When his model Yamaha does not use a choke.

Now some folks will say that what parts are called does not matter. They mostly hang out on TOS.