How do you set the idle

[keithm1961]

I have a 1976 85 hp Johnson, It has gotten, the last two weekends out, where it really doesnt want to idle. If I open the warm idle lever it does just fine but then your locked out of gear. How do I raise the idle at the carb. I looked very quickly and really didnt see an idle adjustment.
I put new plugs in at the beginning of the season. I have to idle for about 10 minutes after start up because the water is so shallow it takes that long to get to deep water. Maybe as simple as a plug change?
If the bleed screw on the tilt trim is loosened the tilt will come down. I rebuilt the valve body all new orings, it works very well. I'm not loosing fluid but the tilt will bleed off slowly, so what I'm wondering if the bleed screw should be replaced because there is a nylon tip on it that is not replaceable, and it could be leaking past that/

 

[jtexas]

Re: How do you set the idle

There's an idle set screw on the starboard side of the motor. It'll be in a spring-loaded nut (to keep it from vibrating out, but it might have done so anyway) on the spark advance lever. It pushes against the block when you screw it in, increasing idle speed by advancing the timing. Don't confuse it with the WOT stop screw, which stops the throttle when the carb butterflies are completely open.

Should be idling at around 800 or so in gear in the water. If it is, and it still dies, the motor needs maintenance.

If the idle set screw goes all the way in and idle speed is still too low, the motor needs maintenance.

Covering up symptoms by increasing idle speed will cost you a piston or two down the road.

What plugs you running? Are they fouling?

 

[keithm1961]

Re: How do you set the idle

I run NGK plugs, they are not fouling, just loading up slightly. The idle is about 500 rpm's, I'll take a look tomorrow and see about turning up the idle screw.
Thanks for the help, I'll let you know the result

 

[HighTrim]

Re: How do you set the idle

I would get rid of the NGKs and put Champions in her, that is what it was designed to run. I pretty much have the whole fleet of 1976 motors, and they run great on the Champs.

Does the warm idle lever dramatically raise the rpms....it should

As stated, be sure that you are not raising the idle past about 850 under load in gear. First ensure that your linkage is properly adjusted and your fuel delivery is working as it should.

Testing of the tnt system hydraulics can get a bit confusing, Ill send you some literature regarding this.

 

[jtexas]

Re: How do you set the idle

+1 vote on the champions. NGKs are great plugs no doubt, but they don't match exactly for heat range. Not so likely to solve your immediate problem, just a better match for the motor.

 

[keithm1961]

Re: How do you set the idle

I would love to see the lit on the hydraulics, as far as plugs I'll give the champs a try, always liked them in a lawnmower,lol. The cam that pushes against the throttle plate had a lot of clearance in it the idle screw ran out of travel I moved the nylon clevis outto lengthen the rod slightly then the throttle had some adjustment, carbs were rebuilt by the previous owner but the engine as never run to check the adjustment.

 

[jtexas]

Re: How do you set the idle

Hold on, if I'm reading you correctly, you screwed yoke (that nylon clevis) farther out, so that the cam is now in contact with the roller?

The yoke is supposed to be a precisely measured distance out. Once installed, it should never be moved.

The throttle cam has nothing to do with idle speed -- the carb butterflies stay 100%closed at idle. Idle speed is controlled entirely with spark timing. The piece where the idle screw is attached, that's the spark advance lever. When it moves to the right, RPMs should increase without the cam ever hitting the roller.

When you throttle up, the timer base has to move first, *THEN* the cam hits the roller and the butterflies start to open up.

If you open the throttle valves too soon, RPMs rise but the spark is late, the motor will just die when you try to accelerate. It might sound fine on the muffs, but wait till you put a load on it.

There's a mark embossed on the throttle cam, and that mark should hit the roller dead center when the throttle is advanced.

If you need more or less idle screw travel, adjust the cable length using that black thumbwheel where the cable enters the cowl. But the cable rarely needs adjusting.

 

[keithm1961]

Re: How do you set the idle

the mark was actually hitting slightly behind the roller, the adjustment I made causes it to hit dead center on the roller, before the adjust ment the screw that moves the spark advance was about an 1/8 of an inch from the block, if i were to bottom the screw it would have just touched the block.

I didnt realize they control idle with ignition timing, that does explain why marine 2 strokes arent peaky like others.