Johnson 9.9HP Throttle Setting

[blubber2023]

Hello,
I have 1979 Johnson 9.9HP. I installed new water pump, impeller, fuel pump, fuel lines, spark plugs. Carburetor cleaned with repair kit. All seems working fine.

I have single handle throttle. I can not start the engine in neutral. If I push throttle arm, it goes in shift and if i push further, i can start the engine. That means i can start my engine in shift but not in neutral.

I removed the air intake box to have access to the throttle linkage and roller.
If i gently push the roller/throttle linkage with my finger, I can start the engine and it runs in neutral with that gentle push on the roller/throttle linkage. If I remove my finger, engine stops.

It feels like initial position of throttle linkage is not correct. How can I adjust that?
The small screw on the plastic part does not help although its all tightened up.

Notes:
In neutral, throttle cam does not touch roller.

Any ideas?

thank you,
Erhan

 

[racerone]

Need to look at the control or post a picture here.-----Most control boxes have a feature where you can disable the shift function for starting and warm up.-----Or hurry to your local friendly boat shop to learn how.-----No need to make any adjustment on motor carburetor linkages at all.

 

[blubber2023]

Thank you for the swift response. My motor can not keep running at idle although its warmed up if the throttle linkage / roller was not pushed gently.

So if I didn't have remote control, i could have the same problem.

thank you,
Erhan

 

[racerone]

On most 2 strokes the cam does not touch the roller.-----It is one of the most misunderstood things on these motors!!-----What trouble shooting have you done ?----Do a compression test and post the numbers here.

 

[OptsyEagle]

You need to make sure your link and sync are set up properly. Not sure precisely on your motor but you will see that as you advance the throttle a throttle cam (metal piece) moves counter clockwise and pushes on the carb roller to provide more fuel. There should be a mark on your throttle cam. As you turn it that mark should be in the center of the roller JUST as the throttle cam touches the roller. If it is not it can be adjusted. Not sure on your model but look for two 5/16" nuts on the starboard side of the motor holding the throttle cam in place. Loosen both to make an adjustment. If it is like my 1976 model you will need a fairly thin 5/16" wrench or plyers OR you will need to remove the flywheel.

It sounds like the link and sync may be off a little preventing the fuel or advance timing you need for starting.

 

[blubber2023]

You need to make sure your link and sync are set up properly. Not sure precisely on your motor but you will see that as you advance the throttle a throttle cam (metal piece) moves counter clockwise and pushes on the carb roller to provide more fuel. There should be a mark on your throttle cam. As you turn it that mark should be in the center of the roller JUST as the throttle cam touches the roller. If it is not it can be adjusted. Not sure on your model but look for two 5/16" nuts on the starboard side of the motor holding the throttle cam in place. Loosen both to make an adjustment. If it is like my 1976 model you will need a fairly thin 5/16" wrench or plyers OR you will need to remove the flywheel.

It sounds like the link and sync may be off a little preventing the fuel or advance timing you need for starting.

thank you for the response, may I also ask you the same question:
Should engine still run at idle speed while the cam does not touch the carb roller? I checked the cam and it seems like when it starts to touch the roller it meets the small mark on the cam. But in my case my engine does not get fuel before cam touches the roller and pushes it by lets say 2mm.

 

[racerone]

Your motor is getting fuel at idle !!----On most outboards the cam does NOT touch at idle.-----And the throttle plate has holes in it.----Calibrated holes to let fuel , air and OIL in at idle.----A 2 stroke idling still needs the correct amount of oil.----That oil comes in with the gasoline !

 

[blubber2023]

Your motor is getting fuel at idle !!----On most outboards the cam does NOT touch at idle.-----And the throttle plate has holes in it.----Calibrated holes to let fuel , air and OIL in at idle.----A 2 stroke idling still needs the correct amount of oil.----That oil comes in with the gasoline !

Thank you,
So what you mean is that:
Even in a condition where the cam does not touch the carburetor roller which means there is no trigger for the throttle plate in the carburetor, motor still should run as throttle plate (butterfly) is designed with the holes allowing fuel/oil/air mixture enough to keep engine running at idle speed.

 

[racerone]

Correct.-----I say it all the time.-----Many folks do not understand the basic concepts of the wonderful 2 stroke engines.----Because the motor still needs fuel ( oil ) for lubrication , the idle speed is controlled with timing.

 

[blubber2023]

When i had cleaned my carburetor i did not open the plug. Maybe i should open it and clean the holes then.
I am talking about the big al plug.

 

[OptsyEagle]

So yes. The motor gets fuel even when the cam is not touching the roller. In other words when the throttle butterfly is completely closed, some fuel still flows to the engine. That said, the question remains if it is getting enough for starting.

I should have added to my post that even though the mark on the cam is aligned properly with the roller, it does not necessarily mean you are synced properly. You probably are, but the better test is to look at the hinge the throttle butterfly rotates on in the carb. Looking directly at the motor you will find it on the left side of the carb. As the roller gets pushed back you can see the throttle butterfly hinge start to rotate. The better way to sync this all up is to place an electrical clip on that hinge with a toothpick or wire or something sticking out of the clip that you can view as you rotate the throttle. You rotate the throttle and at the exact moment that hinge moves the mark on the cam should be in the middle of the roller.

The reason I add this is some older motors, and yours is included in that group in my opinion, will start to see a little play in that roller arm. In other words the roller may move back a small amount BEFORE the throttle butterfly actually starts to open. This little difference can make a big difference in either giving or not giving the motor enough gas to get started.

 

[OptsyEagle]

A little more info so you understand what is going on here a little better. The main reason you want to sync the carb with the throttle cam is not just to ensure you get enough fuel to start your motor, but to optimize the spark timing with the various RPMs the motor will operate at.

So you may know that you want your spark to fire when the piston has just compressed the fuel and is positioned at the top of the cylinder. Piston at top dead center (TDC) it is called. Now electrical sparks are fast BUT NOT INSTANTANEOUS, so when the motor is running faster we want the spark to fire a little sooner then when the motor is running slower, so that the impact of the spark, which takes some fractional time to build, happens when the piston is positioned at TDC. The time difference here is measured in fractions of seconds but it makes a real difference to how your motor runs. As you turn the throttle grip, the amature plate rotates, and by doing so, the timing of the spark is altered. The link and sync is a process where you are synchronizing your spark timing to the RPMs of the motor. And the RPMs of the motors are directly related to how much fuel the carb is providing the motor.

The above is roughtly why link and sync is important. Now to the question about your motor running when the carb butterfly is closed. As you rotate the twist grip for slower speeds you will see that eventually the carb roller stops being pushed by the throttle cam and the throttle buttergly is fully closed. BUT as you keep reducing throttle with the twist grip, your motor continues to slow down. What is happening as you continue to rotate the grip for slower speed after the cam stops pushing the roller, is the fuel now stays the same BUT the spark timing is being changed to fire after top dead center, providing a slower and slower running motor...till it eventually stalls because the spark is happening so far after top dead center that the motor cannot run anymore.

 

[blubber2023]

here is the video of my motor

 

[blubber2023]

here is the video of my motor

I have used a fishing line to pull throttle arm gently. I was able to adjust it with the nuts as you can see in the video but I proved myself why we need idle circuit in the carburetor as throttle arm and butterfly plate resolution is not enough to have stable idling speed.

I cleaned my carb again today and I can confirm small holes in the carburetor for the idle circuit are not blocked. But im still at the same position, i cant have my motor idle, it runs if throttle is pushed.

I will read more about timing and try to understand how it works with my throttle control.