1990 Force 120 2 stroke loss of power high rpm

[Popeye_1990]

I'm not sure what you are adjusting on the carbs but
Adjust the mixture on the carbs. Set all low speed needles to about 1 1/4 turns out from lightly seated. Do not force as this will damage either the needles or the seats.
With the engine idling in neutral, turn each the needles in equally about 1/8 turn at a time. Give the engine a couple of seconds between each adjustment to stabilize. Adjust until the engine either "sags" or stalls. Note this setting.
Now go the opposite direction. Adjust until the engine runs rough, burbles, or stalls. Note this setting.
Set all needles to the average between the two settings: That is, for example, if it stalled at 3/4 turn out and burbled at 1 1/4 out then set all needles to 1 turn out.
Readjust idle speed to 700-750 RPM.
Take the boat out on the water and do a "hole shot"--Full throttle acceleration from a stop. If the engine "sags" then recovers and picks-up it is too lean. Open the needles about 1/16 turn at a time until the engine accelerates with no hesitation.
If the engine sputters or coughs or burbles, then clears itself and accelerates, it is too rich. Close the needles about 1/16 turn at a time until the engine accelerates smoothly.
I can NOT stress this enough! NEVER set the low speed needles less that 1 turns out no matter how poor the idle or acceleration. To do so will run the engine too lean and detonation and melted pistons at or near full throttle operation will result.

Force Power.
Would you mind looking back at the pic I sent of the top view of the carb? The only adjustments I made were to the mixture screws. However there is a white plastic screw just behind the carb cover and in front of the mixture screw. I looked at the parts manual but not exactly certain what this is or does. It is screwed in tightly on both carbs. Is that correct?

Will double check how far mixture screws are turned out. Did I read you right that screws should be no less than 1 1/4 turned out?

Gonna clean plugs today. Hopefully she will get on power. I'll shut down at top speed and pull plugs.

Really appreciate the help y'all

 

[Popeye_1990]

Yes, because it affects the fuel-level in the bowls/float position

...i should have known of that....haha feel stupid asking that now..

 

[Popeye_1990]

I'm not sure what you are adjusting on the carbs but
Adjust the mixture on the carbs. Set all low speed needles to about 1 1/4 turns out from lightly seated. Do not force as this will damage either the needles or the seats.
With the engine idling in neutral, turn each the needles in equally about 1/8 turn at a time. Give the engine a couple of seconds between each adjustment to stabilize. Adjust until the engine either "sags" or stalls. Note this setting.
Now go the opposite direction. Adjust until the engine runs rough, burbles, or stalls. Note this setting.
Set all needles to the average between the two settings: That is, for example, if it stalled at 3/4 turn out and burbled at 1 1/4 out then set all needles to 1 turn out.
Readjust idle speed to 700-750 RPM.
Take the boat out on the water and do a "hole shot"--Full throttle acceleration from a stop. If the engine "sags" then recovers and picks-up it is too lean. Open the needles about 1/16 turn at a time until the engine accelerates with no hesitation.
If the engine sputters or coughs or burbles, then clears itself and accelerates, it is too rich. Close the needles about 1/16 turn at a time until the engine accelerates smoothly.
I can NOT stress this enough! NEVER set the low speed needles less that 1 turns out no matter how poor the idle or acceleration. To do so will run the engine too lean and detonation and melted pistons at or near full throttle operation will result.

Re-read your post on mixture setting. I got it. Thanks

 

[jerryjerry05]

Leave the white alone, it covers a jet, nothing in there to mess with.
It ALWAYS help if you tell us what we're working on. Year? HP?
I see twin carbs so it's a 4cyl. 125 or 120??
The pic of the fuel pump and you say there's a crack?? Kinda blurry.
IF?? there is a crack?? it could be sucking air and not getting enough fuel?
Fuel pump, the older Force pumps just need the diaphragm replaced, the valves work unless they fall apart.
The bogging at 4000 could be the float's not set right?
This is for the new guy's who have little or no experience, don't turn,twist or adjust unless you can restore it back to where it was originally???
Adjust the mixture on the carbs. Set all low speed needles to about 1 1/4 turns out from lightly seated. Do not force as this will damage either the needles or the seats. Tightening the air screw too tight can put a groove n the taper and it will never work right.
Test: starting fluid, start the motor, spray fluid around the motor, under the coils and the base of the carbs, if the spray makes the motor run different?? then a gaskets gone bad and it's sucking air??

 

[The Force power]

Question 3: When I got in the intake manifold where top carb is mounted was covered with condensation and intake was cold to the touch. Is this normal?
I did find a leak where the fuel line connects to fuel pump. Pulled off..cut line and was about to put back on when I saw this.View attachment 350801
Can't see well here but may be a crack or could be that way from manufacturing process.

To Question one;
- I think its just fuel/oil mixture and not necessary grayish??
To Question 3 a & b
-I have seen condensation many times, Why? I have my theory
I'm not sure what I'm looking for in the picture??

 

[jerryjerry05]

Pick up a can of cold soda pop after it's been set out for a bit.
Moisture/condensation forms.
When the carb is drawing air into the carb and past the reeds that cools the metal and condensation forms.
(I did find a leak where the fuel line connects to fuel pump. Pulled off..cut line and was about to put back on when I saw this.View attachment 350801) What's in the pic that you see?

 

[racerone]

You have discovered the basic principle pf refrigeration.----When a liquid vaporizes it needs heat.-----It gets the heat from the metal around it.-----Parts will get cold.-----This is why aircraft have a " carburetor heat " system to prevent icing.

 

[dingbat]

The freezing of the carb throat is the result of the Venturi effect. A reduction in fluid pressure that results when a fluid flows through a constricted section of a pipe.

The Venturi effect can drop the ambient air temperature by 70 degrees Fahrenheit.
The basic operating principal behind a vortex cooling systems

 

[Popeye_1990]

SOLVED!!! Loss of power at high RPM
First let me thank all of you for your help..
After I brought it back in from almost being stranded and got it running again..i called it a day. Next day I went back to marina...attempted to start her and she hit but not crank. Went to squeeze bulb and the bulb collapsed and would not relax. NOW WHAT!!!! ..venting? blockage? Switched to portable tank..same thing. Ah ha!!!! Pulled fuel line that connects to bulb. The inner liner on fuel tank side was cracked and was rolling inward as fuel was being sucked toward motor. Pull bulb. Same thing on both sides of bulb. Cause? Somebody at some point forced a 5/16 fuel line over a 3/8 connector tore inner liner and started whole thing. Grrrr....
Replaced all connectors and bulb to 5/16. Went to O'Reilys and purchased 5/16 auto fuel line and clear inline fuel filter. She runs great! A cheap fuel line geez. Lesson....if people like me would spend more time listening to people like y'all....we would spend less money..

 

[Popeye_1990]

One more question. Carb mixture adjustment...... I followed Forces instruction on adjusting mixture on carbs. Backed out 1 1/14. Started turning back in 1/8 to 1/16 at a time. She wants to run best at just about 3/4 out from seat. I was strictly warned not to for any reason to allow less than 1 full turn.
I have it set right at one full turn. Had to turn idle up to where she will idle at 1000 while in gear....any less...she stalls when pulled back into neutral. Hole shot has a lag...but comes on plane.
Question....is there any way to run it a faction leaner or compensate for the lag without risk of damage ? I can live with it now....but I'm a person that believes; if it ain't right....then it's wrong. Thanks again for all the help. Can't believe y'all do it for free...appreciate it. Gone fishing

 

[The Force power]

One more question. Carb mixture adjustment...... I followed Forces instruction on adjusting mixture on carbs. Backed out 1 1/14. Started turning back in 1/8 to 1/16 at a time. She wants to run best at just about 3/4 out from seat. I was strictly warned not to for any reason to allow less than 1 full turn.
I have it set right at one full turn. Had to turn idle up to where she will idle at 1000 while in gear....any less...she stalls when pulled back into neutral. Hole shot has a lag...but comes on plane.
Question....is there any way to run it a faction leaner or compensate for the lag without risk of damage ? I can live with it now....but I'm a person that believes; if it ain't right....then it's wrong. Thanks again for all the help. Can't believe y'all do it for free...appreciate it. Gone fishing

I'm glad you got it working right.
The original writing / posting said; no matter what do not set the fuel/air-mixture screw less than 3/4 from lightly seated.
BUT with the fuel we run today !!! its "recommended" to go with no less than 1
The idle-settings 750 RPM in gear or 1000 RPM in neutral.

I will post the complete posting, that was written by the late Frank A.
this is one of the many good tools/advices if have received on this site from him and many others still among us.
(I'm just passing on their knowledge)

 

[The Force power]

1.Disconnect the ball link to the carb cam at the timing tower. Disconnecting at the cam risks bending the cam. Move the cam away from the carb roller.
2. Loosen the screw(s) on the aluminum tie bar and let all carbs close completely, then tighten again.
3. Set the cam so that the scribed line is pointing directly at the black roller on the carb lever. If the cam has two closely spaced lines, set the black roller directly between them.
4. The black roller is held with an offset screw and nut. Loosen the nut and turn the screw until the black roller JUST touches the cam. Tighten the nut and re-attach the ball link maintaining the scribed line at the roller.
5. Adjust the ball link so that at full throttle the bottom carb butterfly opens substantially horizontally. Adjust the aluminum tie bar so all carb butterflies open equally at full throttle. They need not be perfect but should be rather close to horizontal for best performance.
6. Adjust timing to 28 degrees before top dead center at full throttle. ( STATIC TIMING / CRANKING SPEED )
7. Adjust idle speed to 700-750 RPM in the water in forward gear. Do this with the screw on the bottom of the timing tower. Loosen the locknut and adjust. Screwing in increases idle speed. Do this in small increments and let the engine rev and adjust itself before the next adjustment. A little goes a long way here. When correct, tighten the nut. Note that the scribed line on the roller will now be (usually) below the black roller a bit.
8. NOW we adjust the mixture on the carbs. Set all low speed needles to about 1 1/4 turns out from lightly seated. Do not force as this will damage either the needles or the seats.
8A. With the engine idling in neutral, turn each the needles in equally about 1/8 turn at a time. Give the engine a couple of seconds between each adjustment to stabilize. Adjust until the engine either "sags" or stalls. Note this setting.
8B. Now go the opposite direction. Adjust until the engine runs rough, burbles, or stalls. Note this setting.
8C. Set all needles to the average between the two settings: That is, for example, if it stalled at 3/4 turn out and burbled at 1 1/4 out then set all needles to 1 turn out.
8D. Readjust idle speed to 700-750 RPM.
9. Take the boat out on the water and do a "hole shot"--Full throttle acceleration from a stop. If the engine "sags" then recovers and picks-up it is too lean. Open the needles about 1/16 turn at a time until the engine accelerates with no hesitation.
If the engine sputters or coughs or burbles, then clears itself and accelerates, it is too rich. Close the needles about 1/16 turn at a time until the engine accelerates smoothly.

10. I can NOT stress this enough! NEVER set the low speed needles less that 1 turns out no matter how poor the idle or acceleration. To do so will run the engine too lean and detonation and melted pistons at or near full throttle operation will result.

 

[The Force power]

SOLVED!!! Loss of power at high RPM
First let me thank all of you for your help..
After I brought it back in from almost being stranded and got it running again..i called it a day. Next day I went back to marina...attempted to start her and she hit but not crank. Went to squeeze bulb and the bulb collapsed and would not relax. NOW WHAT!!!! ..venting? blockage? Switched to portable tank..same thing. Ah ha!!!! Pulled fuel line that connects to bulb. The inner liner on fuel tank side was cracked and was rolling inward as fuel was being sucked toward motor. Pull bulb. Same thing on both sides of bulb. Cause? Somebody at some point forced a 5/16 fuel line over a 3/8 connector tore inner liner and started whole thing. Grrrr....
Replaced all connectors and bulb to 5/16. Went to O'Reilys and purchased 5/16 auto fuel line and clear inline fuel filter. She runs great! A cheap fuel line geez. Lesson....if people like me would spend more time listening to people like y'all....we would spend less money..

lol, I think Redbarron mentioned that in post #2