Carburetor tuning on muffs

[Toshi]

Hi,
I know it’s common understanding (I think) that the carburetor tuning (air-fuel mixture screw adjustment) needs to be performed in water. My understanding of air-fuel mixture screw adjustment is to achieve the highest rpm at idle. Can I adjust the screw on muff first and put the boat on water to adjust the idle rpm?

Thank you.

 

[tphoyt]

Yes you can.
It will get you close but when you have back pressure on the exhaust while in the water and in gear it will change things a bit and that the best time to dial in the fine tuning.

 

[Toshi]

Yes you can.
It will get you close but when you have back pressure on the exhaust while in the water and in gear it will change things a bit and that the best time to dial in the fine tuning.

OK. I will adjust on muffs and fine tune in the water. Thank you very much for the reply !!

 

[havoc_squad]

Remember, in water testing means verifying in gear and boat is not restrained/tied down.

 

[jimmbo]

If the boat is anchored at the Stern, or secured to a Secure Dock, the engine can be adjusted for mixture and Idle Speed while in gear. Just be sure to have the Throttle Cable disconnected at the motor while adjusting, then once the Speed is adjusted, adjust the Cable Length, to provide a bit of Preload to keep the Linkage pressing against the Idle Stop. Too little and the Idle Speed can end up being inconsistent, too much and shifting in and out of gear can be difficult

 

[909]

You're always going to be a little low when tuning in a bucket or muffs , so be prepared to add more once it's in the water

 

[saltchuckmatt]

You're always going to be a little low when tuning in a bucket or muffs , so be prepared to add more once it's in the water

You mean a little lean, right?

 

[oldboatfixerupper]

So 1 1/4 turn is the starting point? Also I thought you wanted low rpm at idle so you don't have clunking when shifting into gear,

This is the best way to get it right with this tool?

 

[saltchuckmatt]

So 1 1/4 turn is the starting point? Also I thought you wanted low rpm at idle so you don't have clunking when shifting into gear,

Idle rpm's and low speed air fuel mixing are two different things.

 

[saltchuckmatt]

So 1 1/4 turn is the starting point? Also I thought you wanted low rpm at idle so you don't have clunking when shifting into gear,

This is the best way to get it right with this tool?

Hey mate, they don't like you cherry picking someone else's thread. Keep the questions to your thread. No worries.

 

[jimmbo]

Most engines have an in gear idle speed of about 600-650rpm, which in neutral could be any where from 675-1000, depending on what load was on the engine while in gear. A change in Propellers can result in a change in the In Gear Idle rpm.

Most Idle Mix screws/needles are set at 1 1/2 from lightly seated, and the Final Setting is 'Usually' Leaner than that, but not always.

As for what the Image was, I have no idea, what it was.

 

[saltchuckmatt]

Most engines have an in gear idle speed of about 600-650rpm, which in neutral could be any where from 675-1000, depending on what load was on the engine while in gear. A change in Propellers can result in a change in the In Gear Idle rpm.

Most Idle Mix screws/needles are set at 1 1/2 from lightly seated, and the Final Setting is 'Usually' Leaner than that, but not always.

As for what the Image was, I have no idea, what it was.

Oldboatfixerupper has his own thread....."1974 115"

He just highjacked this one because he didn't know better.

I think that tool is a carb synchronizer...probably for motorcycles.

 

[ct1762@gmail.com]

that tool does look like a vacuum synch tool only used on 4 strokes. i have one at the shop for the odd 4 stroke that comes in, but 95% of the time its not needed as the factory sets it and they dont really ever get out of adjustment.

 

[jimmbo]

factory sets it and they dont really ever get out of adjustment.

Until some owner with 10 thumbs starts turning every adjustment in sight, to make it run better, you know turn that 90 into a 115/140...

 

[ct1762@gmail.com]

Until some owner with 10 thumbs starts turning every adjustment in sight, to make it run better, you know turn that 90 into a 115/140...

this is very true, but its pretty easy to tell if they are out of balance IMO

 

[jimmbo]

I never worried about balance, I would just adjust and readjust for best Idle, the add 1/8 of a turn rich

 

[Toshi]

On my 1989 Johnson 2 stroke (3cylinders), I was trying to adjust the air-fuel mixture.
Then I noticed whichever direction I turned the screw of the middle carb, the rpm wouldn’t change. Any idea?? Maybe, the tip of the screw is broken? If so, can I just unscrew all the way to check or do I have to be careful about something?

I could hear the rpm changes when turn the screws on the top and bottom carburetor.
Thanks !!

 

[tphoyt]

I can’t remember what your working on but I recall you were going to clean the carbs.
Did you not remove the needles when you cleaned them?
Also have you verified your getting fuel to that carb and spark to that cylinder?
It is possible for it to run on just 2 cylinders and run pretty well at idle.

 

[Toshi]

Hi tphoyt,
Yes. I cleaned the carbs, but not needles.
Any precautions that I should take when I remove it? I can hardly find any info about removing it.

Also, how can I verify I am getting fuel to the middle carb?
I will re-check the spark tomorrow on the middle carb.

For reference, I checked spark plugs and all look the same after running on the water today.

As you mentioned, it ran pretty well at idle after tuning top and bottom carb tuning.

I can’t remember what your working on but I recall you were going to clean the carbs.
Did you not remove the needles when you cleaned them?
Also have you verified your getting fuel to that carb and spark to that cylinder?
It is possible for it to run on just 2 cylinders and run pretty well at idle.

 

[jimmbo]

On my 1989 Johnson 2 stroke (3cylinders), I was trying to adjust the air-fuel mixture.
Then I noticed whichever direction I turned the screw of the middle carb, the rpm wouldn’t change. Any idea?? Maybe, the tip of the screw is broken? If so, can I just unscrew all the way to check or do I have to be careful about something?

I could hear the rpm changes when turn the screws on the top and bottom carburetor.
Thanks !!

Perhaps the screw was backed out so far, that it didn't make any real difference to the Mixture, or there was some gunk/gum/varnish in the passages that were restricting the flow and the needle wasn't making any change in the range you turned it.
Another possibility is that the Middle carb wasn't fully closed, and that certainly will affect the idle circuit