Can you offer some places to start with my 79 Johnson 55 problems?

[Daviet]

Re: Can you offer some places to start with my 79 Johnson 55 problems?

Try using an inductive timing light and check each plug wire and see if one of them is loosing spark when the engine flutters.

 

[BillaVista]

Re: Can you offer some places to start with my 79 Johnson 55 problems?

That's a good idea, I'll try that tonight.

I did a decarb according to these instructions:

Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

It did indeed smoke like Cheech and Chong! I believe there was some improvement, even accounting for the placebo effect, it seemed to run smoother...but it didn't change that stumble/miss evident in the video.

 

[BillaVista]

Re: Can you offer some places to start with my 79 Johnson 55 problems?

OK, so I haven't been able to detect and problems in the ignition system.

So I took the carbs and leaf plates off. Found a couple of interesting things that might explain my problems.

First - a question on the carbs - is this normal. That is - is it normal for the centre nozzle/tube to be offset to one side as the pics below show?

 

[BillaVista]

Re: Can you offer some places to start with my 79 Johnson 55 problems?

Now, on to the more interesting bit.

When I took the leaf-plate assemblies off I discoverd some kind of black plastic cap lodged in one of them. It looks pretty chewed up. I have no idea how it could have gotten in there or how long it might have been in there, but I'm thinking that, at the very least this cannot be helping?

Then I held them each up to the light. One looked like this, which seems ok to me:

But one has 3 leafs on one side that do not close completely. I'm thinking this won't help the engine idle well, and may also explain the excessive oil back through the carbs and into the air silencer and from their leaking into the engine case and water?

Questions:

1) Would it help to take this leaf set out, flip it around, and install the other way? Or is it just worn and needs to be replaced?

2) I cannot seem to find the leafs themselves available anywhere online, and most places list the whole assembly as unavailable / obsolete. I did find one place that might have the whole assembly in stock. Should I go ahead and order two and replace both whole assemblies for good measure, or is it not like brakes and u-joints and such and it's ok to just replace the one? They run about $100 each!

 

[BillaVista]

Re: Can you offer some places to start with my 79 Johnson 55 problems?

Well, I figured a leaf-flip is probably not a good long-term solution, but I wanted to know if I'd hit on anything so I flipped the leaf, cleaned the carbs, removed the little plastic plug, and buttoned everything up.

Didn't change a darn thing - still stumbles/misses at idle like in the video and still won't start if it quits before it's warm.

 

[BillaVista]

Re: Can you offer some places to start with my 79 Johnson 55 problems?

I used a cool tool a mechanic friend lent me - it's a Mac tool that measure peak spark voltage in Kv with s sensor that hooks on the high tension wires.

The upper cylinder coil had readings all over the map from 2 to 9 Kv, and the readings changed randomly and did not correspond to the stumble/miss.

The lower cylinder coil I couldn't get to read anything, despite the fact that the cylinder is clearly firing (as evidenced when you pull the boot) and it has good spark when you pull the plug and crank the engine.

So, I'm stumped and I guess I'm going to have to just throw some parts at it and see what happens.

Going to start by replacing the coils and the fuel pump and go from there. Going through the carbs and fixing the leaf plates (reed valves) didn't change anything.

I hate it when diagnosis comes to this but I don't know what else to try / check. I have bad memories of an old 2-stroke dirt bike where I replaced darn near everything until one day I realized the woodruff key holding the flywheel/mag onto the crank was broken so it would slip and constantly change the timing so sometimes it would run, and sometimes not!

 

[Bosunsmate]

Re: Can you offer some places to start with my 79 Johnson 55 problems?

Have you tried a timing light on every cylinder?
A timing light cost me $12, pretty cheap compared to buying unnecessary electrics

 

[Bosunsmate]

Re: Can you offer some places to start with my 79 Johnson 55 problems?

Also have you run the ohmn readings on the timing base and stator?
Ive seen these stumble and miss from a shiortened stator to flywheel magnet.
A chief mechanic sold one to me cheap as he couldnt work it out but once i popped the flywheel the sorch mark on the stator said it all. No more was that a parts motor. All i did was re-coat it in epoxy and that stumble disappeared off to infect someone elses motor