20 H.P. Johnson - Will Not Continue Running

[chuckp]

Hello Folks,

I've search the forums and read the top secret files although I have not found my exact issue.

I have a 1971 20 hp Johnson manual start tiller motor model no. 20R71S. I recently purchased this motor and do not know much history. Issue started with too much gas coming out the front of carb and plugs fouling.

I rebuilt the carb with a Johnson kit from BRP replacing the float, float needle, washers, main gasket and carb to head gasket. Cleaned and made sure all passages were clear with compressed air. Also manually cleaned the high speed jet with a piece of copper wire. I set the float per the TS carb post and set the low speed jet per that TS post.

Vented gas tank, connected fuel line in proper direction and pumped up primer bulb and motor started right up. Motor runs ok with a little throttle for about 45 seconds. While trying to adjust low speed jet, motor starts spitting and dies. Plugs look better although I have to set the low speed jet to about 1/2 to 1 turn from gentle seat to get plugs to be dry and golden brown in color.

After this motor will only run for about 5-10 seconds running rough and spitting. I try to advance throttle but this bogs the motor and it dies. After awhile the motor does not want to start and run anymore unless I let it sit for awhile or pull the plugs and cycle engine to dry it out. Best results come when I let it sit for an hour or so and then start the process again.

Spark plugs are brand new Champion J4J replacements (J4C) - it has blue arc with plugs about 1/4 away from block bolt and the primer bulb is firm but not tight. Fuel no longer runs out front of carb and drips on inner cowl but is slightly evident at front of carb.

Motor pumps water while it's running - it seems like I'm close to getting this motor running properly but I must not have something adjusted correctly or maybe it's sucking in air somewhere?

Chuck

 

[Cofe]

Re: 20 H.P. Johnson - Will Not Continue Running

Did you replace any fuel lines? 1970's rubber is purdy old and will contaminate a carb quickly. Are you using new fresh fuel at 50/1 mix?

 

[Daviet]

Re: 20 H.P. Johnson - Will Not Continue Running

Does the engine spit out of the carb or exhaust?
Just a thought, try setting the low speed jet at 1 1/2 turns out and see if it will start. I don't think I have ever ben able to keep one running that lean at an idle. Usually the plugs will be a little damp after idleing.

 

[chuckp]

Re: 20 H.P. Johnson - Will Not Continue Running

Have not replaced fuel lines, I don't see any trash in the carb after I take it back apart while re-checking the float. I could try some new fuel/oil although this same tank runs fine on my Johnson 15 hp.

Sorry, by spitting I mean popping or running rough, maybe I need to go back to 1 1/2 turns out from seat on the low speed but it operates the same as in my original post - the plugs just look wet at 1 1/2.

 

[Daviet]

Re: 20 H.P. Johnson - Will Not Continue Running

Is it popping out of the carb or exhaust?

 

[chuckp]

Re: 20 H.P. Johnson - Will Not Continue Running

I'm kinda new to working on these motors - how would I tell? I want to say it was the exhaust but don't really know how to tell!

 

[Cofe]

Re: 20 H.P. Johnson - Will Not Continue Running

If you are using water muffs try this..... Keep ignition off, remove spark plugs, turn water on, and spin the motor over for about 10 seconds. Take a flash light and look in the cylinders for any evidence of water. If water is getting in the cylinders, we need to address a different situation.

 

[Daviet]

Re: 20 H.P. Johnson - Will Not Continue Running

If it was spitting out of the carb it would try to spray fuel out of the carb back towards you.
Usually popping or spitting out of the exhaust is a sign of a lean mixture.
If you cannot control the low speed mixture by adjusting the jet, it might be time for a carb overhaul.

 

[Monte1961]

Re: 20 H.P. Johnson - Will Not Continue Running

Does it seem as though when you throttle up that it wont RPM and starts to bogg down? There is a flat rubber ring, (should have came in your kit) that fits around the high speed jet. If it isn't in place, engine will run at idle and not at past mid throttle. Just a thought. Post back and let us know.

 

[chuckp]

Re: 20 H.P. Johnson - Will Not Continue Running

I've been putting the motor in a trash can filled with water to run it - I can pull the rope and look in the cylinders for water.

The motor is definitely popping out of the exhaust - what kind of carb overhaul can I do other than putting a carb kit in? Replace the low speed jet needle or something else?

Thanks,

Chuck

 

[Daviet]

Re: 20 H.P. Johnson - Will Not Continue Running

When you overhaul the you clean all passages and install new gaskets.
Try to richen up the low speed jet first.

 

[chuckp]

Re: 20 H.P. Johnson - Will Not Continue Running

Does it seem as though when you throttle up that it wont RPM and starts to bogg down? There is a flat rubber ring, (should have came in your kit) that fits around the high speed jet. If it isn't in place, engine will run at idle and not at past mid throttle. Just a thought. Post back and let us know.

I remember a flat rubber ring washer under the bowl drain screw but I did take the high speed jet out, just made sure it was clean and had no obstructions. After the initial start and 45 secs of running, the motor will not idle very well and runs rough, even when advancing the throttle at which point the motor bogs and dies.

 

[chuckp]

Re: 20 H.P. Johnson - Will Not Continue Running

When you overhaul the you clean all passages and install new gaskets.
Try to richen up the low speed jet first.

I overhauled the carb with new float and float needle and replaced the carb to head gasket and larger internal gasket between the carb halves. I also made sure all the passages where clear. I do have a mostly square gasket that has a number of open passages in it that I do not see in my carb.

So maybe crank out the low speed jet some more?

 

[Cofe]

Re: 20 H.P. Johnson - Will Not Continue Running

Yepp.....One and a half turns out is initial setting. In is leaner, out is richer.

 

[chuckp]

Re: 20 H.P. Johnson - Will Not Continue Running

Hey Folks,

Does anyone know what the plastic part is with the red arrow point to it in the photo on a 1971 20 hp Johnson tiller motor model number 71R20S? It has a metal half loop underneath and I do not know what it is used for.

Thanks,

Chuck

 

[chuckp]

Re: 20 H.P. Johnson - Will Not Continue Running

Looking at the BRP parts web site, this appears to be the lockout lever with guide spring underneath - whatever that is!

Ahhh - maybe to keep a person from starting the motor in gear?!

 

[Daviet]

Re: 20 H.P. Johnson - Will Not Continue Running

It will not let the recoil start the engine if it is in gear, unless it has been disabled.

 

[chuckp]

Re: 20 H.P. Johnson - Will Not Continue Running

Hello Folks,

I tried cleaning the carb one more time by soaking it in carb cleaner for 24 hours after taking it apart and removing all the gaskets and plastic parts. After that I removed the carb from the cleaner and air dried it out. I had to re-adjust the float screw one more time to make the float level when upside down. The motor fired off on the fourth pull and ran OK as I adjusted the low speed needle valve per the procedure in the top secret files: http://forums.iboats.com/showthread.php?t=167352

The procedure is correct, after the initial 1 1/2 turns out from gentle seat and adjustment in to reach smoothest idle, the slow idle needle valve had about a 1/4 turn area where it liked to run smoothest without popping or flooding out. I had to fine tune the throttle linkage (throttle had been advanced) to get everything running well but it seems to have taken care of my issue.

The motor has been starting on the first or second pull and running as smoothly as an older 2 cycle can at idle - thanks for all the help here and on this forum to solve this problem!

Chuck

 

[Monte1961]

Re: 20 H.P. Johnson - Will Not Continue Running

Thats what were here for Chuckp! Glad to hear all is good and happy boating. Now go have fun, with all the work you have done! You deserve it.