88 Force 85hp (3 cylinder). Engine sputters under heavy acceleration from idle.

[Nordin]

When you open up (CCW) the air/fuel mixture screw you allow more fuel to mix with the amount of air that is drawn in to the crank case.
It is ejector effect and air velocity that regulates the mixing and when you set the mixture richer by open up the screw, more amount of fuel allows mixing with air.

 

[jerryjerry05]

Until you get the rpms set right??
You can adjust the air screws all day and not accomplish the task?
Factory recommends 1 turn out.
Mine ran great for YEARS at that setting.

 

[racerone]

I don't think you can MELT a piston by setting the LOW SPEED MIXTURE too lean.----Why is this acceleration concept so difficult to understand ?----Remember there is no accelerator pump on these carburetors.----They wanted to keep it simple !!

 

[Nordin]

I do not remember where I have read about this but the low speed mixture does not completely stop working at high speed and WOT.
The low speed circuit is also acting at higer speed.
But I can be wrong.
I have always set when I adjusted said to other that asked to not go lower then 1 turn out from seated.

To lean mixture can end up with a melted piston.

 

[racerone]

I do not believe you can melt a piston with idle mixture set too lean !!

 

[DunbarLtd]

I do not believe you can melt a piston with idle mixture set too lean !!

If the oil is mixed with the fuel and that fuel is needed for proper lubing, then what makes you think a lean condition would not cause excess friction (heat) and damage the combustion chamber in some way. Whether its a piston, ring, or the walls.

Care to explain for those of us who dont understand? Im always willing to learn something new.

 

[DunbarLtd]

Until you get the rpms set right??
You can adjust the air screws all day and not accomplish the task?
Factory recommends 1 turn out.
Mine ran great for YEARS at that setting.

Hmm Ok. Well I guess i need a tach then if i really want to fine tune this damn thing. Thanks for sharing.

 

[racerone]

Sorry, ----Not sure why you can not accept the fact that you can NOT melt a piston with the low speed mixture set too lean.------I also say that the whole concept of mixing oil to the fuel and 2 stroke lubrication is not well understood.-----Let me ask you what you think happens when 2 stroke fuel enters the carburetor !

 

[The Force power]

Hmm Ok. Well I guess i need a tach then if i really want to fine tune this damn thing. Thanks for sharing.

There you go and focus on that! (and:drum: stay on the rich side)

 

[Nordin]

Well now I remembered where I got information about the low speed mixture setting and that it can cause melted pistons if too lean.

It is in Frank Acamporas sticky topic "synchronizing carb and timing Chrysler/Force" in the top of this forum.
In thread "Chrysler and Force FAQ and other great information".

Read point #10 about not to set the low speed mixture screw less then 3/4 turn out.

I never set it leaner then 1 turn out from seated.

 

[racerone]

The facts are clear.-----Many folks do not understand the setting of the low speed mixture and what that does to operation of the engine !!!

 

[Nordin]

Well we have different opinion about the low speed mixture and we leave it there.
Hopefully we do not give bad or wrong advise to folks who asks about the settings etc and how to tune the engine.

 

[racerone]

Can you explain why some automatic oiling systems REDUCE the amount of oil added to the gasoline at idle ?

 

[DunbarLtd]

Can you explain why some automatic oiling systems REDUCE the amount of oil added to the gasoline at idle ?

I dont know enough about this 2 stroke outboard carburetor system to really have an educated opinion. That is why I asked here.
I was simply looking at it from a common sense point of view and what I know about other carb systems out there. This is my first 2 stroke outboard and obviously there are some differences.

If you have some knowledge about the subject then please do us all a favor and share it. A lot of people out there could benefit from the information.

Back to the discussion.....aside from the issue of overheating, what is then the worst case scenario with an over leaned 2 stroke outboard engine with premix, in your opinion? I do not have a auto oiler so i do not believe that is relevant to this discussion. Id like to keep it on topic if we can. Thanks.

 

[DunbarLtd]

Until you get the rpms set right??
You can adjust the air screws all day and not accomplish the task?
Factory recommends 1 turn out.
Mine ran great for YEARS at that setting.

On my carbs body it says WE 18-1A for top carb and middle and bottom are WE 18-2A.

Are these Tillotson? I cant find any info on them whatsoever online. Super frustrating.

 

[The Force power]

I dont know enough about this 2 stroke outboard carburetor system to really have an educated opinion. That is why I asked here.
I was simply looking at it from a common sense point of view and what I know about other carb systems out there. This is my first 2 stroke outboard and obviously there are some differences.

If you have some knowledge about the subject then please do us all a favor and share it. A lot of people out there could benefit from the information.

Back to the discussion.....aside from the issue of overheating, what is then the worst case scenario with an over leaned 2 stroke outboard engine with premix, in your opinion? I do not have a auto oiler so i do not believe that is relevant to this discussion. Id like to keep it on topic if we can. Thanks.

DunbarLtd,

I don't think the question was directed to you speciously, the worst case scenario could be burning up pistons/scoring cylinder-walls
(NOT SOMETHING YOU WANT TO DO)
make sure your timing is not too retarded to prevent over detonation

On the side of the carbs does it not say Tillotson? are you trying to determine if you have the right carbs on it?

 

[Nordin]

When we talk about low speed mixture we talk about the ratio air/fuel (gas mixed with oil) not the ratio of mixture gas/oil.

You will have the same issue in a 4 stroker, to lean mixture of air and fuel ....... hotter cumbustion.

Leaner mixture of air/fuel leads to hotter cumbustion in the cylinder and if to lean it will create detonation and at the end the piston will be hurt (start to melt). More fuel in the mixture relative to air will cool the cumbustion.

If you have lean conditions you either retard the timing or rich the mixture or both.If not you will ruin the piston/cylinder.

I do not know for sure about these Walboro or Tillotson which are at Chrysler/Force engines if the low speed circuit also is active at higher speed and WOT.

But I believe it, because from the sticky topic from Frank Acampora who was the guy who had most experience from these engines at this forum and he highly recommend not to set the low speed needle less then 3/4 turn out from seated,

What I know is that to lean conditions in the cumbustion camber leads to hotter cumbustion and the temperature will rise dramatically.

 

[DunbarLtd]

DunbarLtd,

I don't think the question was directed to you speciously, the worst case scenario could be burning up pistons/scoring cylinder-walls
(NOT SOMETHING YOU WANT TO DO)
make sure your timing is not too retarded to prevent over detonation

On the side of the carbs does it not say Tillotson? are you trying to determine if you have the right carbs on it?

Id like to find some type of documentation for these carbs if possible. One that illustrates and specifies parameters, tolerances, settings, etc, etc.

 

[DunbarLtd]

When we talk about low speed mixture we talk about the ratio air/fuel (gas mixed with oil) not the ratio of mixture gas/oil.

You will have the same issue in a 4 stroker, to lean mixture of air and fuel ....... hotter cumbustion.

Leaner mixture of air/fuel leads to hotter cumbustion in the cylinder and if to lean it will create detonation and at the end the piston will be hurt (start to melt). More fuel in the mixture relative to air will cool the cumbustion.

If you have lean conditions you either retard the timing or rich the mixture or both.If not you will ruin the piston/cylinder.

I do not know for sure about these Walboro or Tillotson which are at Chrysler/Force engines if the low speed circuit also is active at higher speed and WOT.

But I believe it, because from the sticky topic from Frank Acampora who was the guy who had most experience from these engines at this forum and he highly recommend not to set the low speed needle less then 3/4 turn out from seated,

What I know is that to lean conditions in the cumbustion camber leads to hotter cumbustion and the temperature will rise dramatically.

Thank you! I understood what ratio we are adjusting. I did not think we adjust the gas/oil with the air screw. Obviously that ratio is premixed in the tank.

I just didnt know if that "air" screw allowed more air or more fuel. Sounds like it allows more fuel? I have a Seloc manual and have been going through the fuel section to further understand this system. I appreciate the comments.

 

[Nordin]

Dunbarl .... find a factory service manual for your engine.which is the best.
Check at Ebay they will come up sometimes.
Seloc and Clymers are good in some parts (Clymers the best of these two in my opinion) but they will carry out all models and Hp range and then they are not so detailed.

I think the factory manual also contains the high speed jets setting depending which elevation/altitude you are in.
The high speed jets are fixed and you have to change them if you go to a higher or lower that the jets are for.

The high speed jets manage a big range in elevation until you have to change them.