1987 Force 125 Idle mixture screws

[sidenberg]

Engine runs perfect through all rpms only when the idle mixture screws are turned 3/4 turns from seated. Specs call for 1 1/4 turns. I am a bit worried about damage running it this lean. If I turn the screws any richer it still runs fine at WOT and it starts and idles just fine, but it will run very rough,or shutters, between about 1200 to 2500 rpms. Should I be concerned with running it this lean? Or is this an indicator that something else is amiss? Regardless of how the idle screws are set the engine smokes rather a bit until it hits about 2500 rpms and then clears up. I have heard this is common in older models, yes?

 

[jerryjerry05]

Re: 1987 Force 125 Idle adjustment screws

Re: 1987 Force 125 Idle adjustment screws

Those screws are for idle air set them at 1 1/8-1/4.They affect nothing at WOT.Do a compression test and a decarb.Ethanol in your fuel is affecting a lot of motors.It just doesn't run as good.
Outboard are made to run FAST!!! at slower speed they don't run as well. Especially Force/Chrysler.J

 

[sidenberg]

Re: 1987 Force 125 Idle adjustment screws

Re: 1987 Force 125 Idle adjustment screws

Thank you Jerry for your reply. I understand the idle mixture screws do not affect the engine at WOT. When my idle screws are set richer than than 3/4 turns (1 1/4) it still idles perfect but when put in gear and underway it bogs down and shutters between 1500 rpms to about 2500 rpms but above that then runs fine.

When idle screws set at 3/4 turns, the motor runs smooth through at all rpms but still smokes a lot as it does at 1 1/4 turns, until it gets above 2500 rpms. I understand that running too lean can burn out cylinders but why would it run better at the lower rpms at this lean setting and not with richer setting? And why all the smoke at the lower rpms regardless of the position of the idle screw settings? Could improper timing cause this?

The compression checks out at 130 +- and I have decarbed with sea foam, however I can still see some carbon on the pistons when viewing through the spark plug holes. Could carbon buildup be the cause?

 

[foodfisher]

Re: 1987 Force 125 Idle adjustment screws

Re: 1987 Force 125 Idle adjustment screws

My smoke issues cleared up when I cleaned the fuel recirculation system. '86 125hp

 

[sidenberg]

Re: 1987 Force 125 Idle adjustment screws

Re: 1987 Force 125 Idle adjustment screws

Foodfisher. I was thinking about that. How did you clean the fuel recirculation system?

MMM, I wonder if this could also be the cause for my engine to require a lean mixture. Common sense says if the recirculation is plugged then fuel buildup may occur in the carbs resulting in a richer mixture even though the screws are set lean. Makes Sense aye?

 

[foodfisher]

Re: 1987 Force 125 Idle mixture screws

Don't know where it recirculates to. Only know it worked to clear up the heavy smoke prob.

 

[jason32038]

Re: 1987 Force 125 Idle mixture screws

The spec for starting at 1 1/4 turns from a light seat should be the starting point in adjusting the mixture. My 86' 85hp has 3 carbs and the spec for that is 1 turn from a light seat.

 

[moparman]

Re: 1987 Force 125 Idle mixture screws

The rec system allows excess fuel from the manifold to be drawn back into the crankcase and be burned as needed to prevent overly rich running,if you trace the lines ,you will find they go back along the side of the motor [fuel pump side] to do this. The smoke your seeing is most likely excess fuel being burned instead of going back to the crank case to be metered correctly as needed.