Carb Tuning, when things don't go as planned

[asdasc]

Hi All,

I am working on my '58 Johnson 18hp, and have questions. I read, understand and followed the instructions here on how to tune it, but things didn't go as planned, and there isn't much info out there on what to do next. The carb is recently rebuilt, and the engine seems to work pretty good, just not a lot of power (which may be normal)

When I do the high speed run and start dialing in the high speed jet, nothing changes in RPM or performance. I got it all the way in, and let it run like that for 30-45 seconds, and it just kept running.

What is that a symptom of? What can I check next? I have good compression and spark, the thing runs smoothly, but it just doesn't seem like things are right if the high speed adjust doesn't do anything.

I am looking for ideas.

Thanks,

 

[asdasc]

Re: Carb Tuning, when things don't go as planned

I am starting to wonder if this has never happened to anyone before.

Maybe the packing nut was too tight, and it was hard to turn and just being hard to get at I didn't have it all the way in? It sure seemed like it.

 

[Joe Reeves]

Re: Carb Tuning, when things don't go as planned

Those brass packing nuts should be just tight enough so that the needle valves do not turn due to vibration BUT not so tight that you cannot turn them easily.

Possibly you have the needle valves switched. The one that has the needle type point is the top slow speed needle valve. The rather blunt pointed valve is the high speed.

If you have them installed correctly and indeed have the high speed valve screwed all the way in, you've overlooked something in that carburetor.

Loosen the packing nut temporarily and check to see if the valve will easily turn in further.

 

[asdasc]

Re: Carb Tuning, when things don't go as planned

Hi Joe,

Thank you very much for the response. Maybe I did reverse them when rebuilding the carbs. I will loosen the packing nuts and check it out the needles to see if they got swapped. I never thought of that as a possibility.

I had to tighten down that packing nut pretty hard, as it was leaking fuel out there at first. It was just little drops, but it stopped when I tightened them down good.

I won't be back out there until the weekend, but I sure feel better now knowing I have some things to investigate.

Thanks again,

 

[Joe Reeves]

Re: Carb Tuning, when things don't go as planned

Also, if the needle valves are installed properly, make sure that you have that thick cork gasket installed on the bottom nozzle area of the top carburetor body.

 

[asdasc]

Re: Carb Tuning, when things don't go as planned

Do you mean part 57?

 

[Joe Reeves]

Re: Carb Tuning, when things don't go as planned

Yes, part 57.

 

[asdasc]

Re: Carb Tuning, when things don't go as planned

OK thanks, I'll check it out.

 

[asdasc]

Re: Carb Tuning, when things don't go as planned

Hi Joe, Last weekend I rebuilt the carb on this, and you were right! Instead of the thick gasket there, I had put 2 of the thinner ones that came in the kit. They looked more like extra needle valve packing washers. When I did this last, it was my first carb rebuild ever on an outboard.

Now that I have the cork float replaced with plastic and the correct gasket in position 57, the carb tunes just like it says it should in your FAQ!

I did struggle a bit with bad gas, but now I am all set and things are running great. Thanks for all the help.