4 hp johnson will not start need help has compression and spark

[byronjacobson]

I made a mistake and volunteered to try repair a 4 hp johnson for my former dentist. He used to help me out with tooth aches on the weekend so i figured i owed him a favor. this is a 1976 model 4w76m. The compression checked out around 58 to 60 pounds on both cylinders. It also has a fairly good spark. I cleaned the carb and thought that was all the motor might need. After doing this, i pulled the starter rope and nothing is happening. I put some gas in the spark plug holes and also used some starter spray in the carb and still nothing, no firing or anything.
Today I spent a couple of hours pulling the flywheel. I gapped the points at 0.020 and cleaned the points running a brown paper bag between the points. I also took the ignition plate off and noticed that the wires running under the ignition plate seemed to be wearing or rubbing against the plate. I rerouted the wires. since the flywheel seemed to be running into some kind of restriction when rotating it, I ended up also repositioning one of the coils. the plug wires say they are kypalon ignition copper conductor wires. Put everthing back together, saw I still had spark and tried to start the motor again. Except for a very occasional pop, nothing would fire. I tried putting gas in the spark plug holes and also using starter spray but still nothing.

tomorrow if i get time , i thought i would take the carb off again and see if that helps. seems like the plugs stay dry and don't get wet. Was wondering if this motor has a blocked reed valve. How does one check a reed valve on a motor of this type. I don't even know where they are located. Also looked at the bushing for the shear pin. It seemed fairly good, but there is a very small amount of play. Could this cause the timing to go off enough not to fire?

I am getting tired of spending time and this motor and need some help and ideas. It is not in my nature to give up but I don't want to spend all summer on this motor. Please help. You can email me at jake331@charter if you prefer.

 

[Bosunsmate]

Ground the spark plugs leads on the block then turn it over a few times. Then pull the spark plugs, if they arent wet then then you do have a problem with fuel delivery for sure. If they are wet you might have a timing issue. If thats the case then the reason as to why they would of being dry when you removed them iinitially would of being that the fuel was being burnt keeping those sparks dry but it was happening at the wrong time.
Some people accidentally put the plug wires on to the wrong cylinder and that makes the engine 180deg out of time and you get this exact symptom you describe- having spark and fuel poured direct into cylinder yet no action.

If they are still dry try spraying some manually down the carb throat with a spray bottle. That bypasses the carb. If they get wet then then the problem will be in the carb or back from there to the fuel tank.
If they are still dry while spraying into the carb then that indicates your reeds or seals. You can tell which seal depending on which plug is dry. Its unusual for both seals to go at once. Unusual for reeds to go, thats normally one of the last things i check, not saying it doesnt happen though

 

[byronjacobson]

I did try switching the plug wires to see if they had been connected backwards. today if i get time, I'm going to try set the timing using an ohm meter. There was a web site on the internet that explained how to do this. I'm wondering if i'm getting spark at the wrong time. I have tried putting starting fluid down the throat of the carb and also putting gas directly into the spark plug chamber.
You mention bad seals. Where are these seals located you are talking about?
I'm hoping that if i get the timing set better, the motor will at least fire once in a while.
do you know if hypolon ignition copper conductor plug wires are the right wires? I understood older motors used different plug wires compared to newer car engines.

 

[F_R]

Maybe you are beating a dead horse. 58-60 psi Compression is pretty low. You might get it to run on that, maybe not. Should be up around 80.

 

[AlTn]

7 mm hypalon copper ignition wires are correct....spark should jump a 1/4" open air gap with a blue snap

 

[Bosunsmate]

I did try switching the plug wires to see if they had been connected backwards. today if i get time, I'm going to try set the timing using an ohm meter. There was a web site on the internet that explained how to do this. I'm wondering if i'm getting spark at the wrong time. I have tried putting starting fluid down the throat of the carb and also putting gas directly into the spark plug chamber.
You mention bad seals. Where are these seals located you are talking about?
I'm hoping that if i get the timing set better, the motor will at least fire once in a while.
do you know if hypolon ignition copper conductor plug wires are the right wires? I understood older motors used different plug wires compared to newer car engines.

top and bottom of crank shaft, again unlikely if you a putting fuel in spark hole and no fire

 

[byronjacobson]

today i spent a couple more hours trying to set the timing using a VOM. I put the motor back together again and still nothing fires. I still have spark however. Checked the plugs again and noticed they were still dry. unplugged the plug wires and pulled the starter rope and then rechecked the plugs and they were still dry. tried spraying starter fluid in the carburator but it still wouldn't fire.
tomorrow I thought i would take the carb off a second time and go thru and clean the carb again. where are the reeds located and how does a person check to see if stuck reeds would be causing this problem.
i'm hoping i can found something in the carb that is causing my problem.
still looking for ideas from any of you guys out there in the iboats community. thanks to you who have replied so far.

 

[F_R]

Three things are necessary for an engine to run:
1. Fuel and air in the correct proportions
2. Spark strong enough to fire the plug under compression, and at the right time
3. Enough compression

In addition a two-stroke needs crankcase compression.

 

[Bosunsmate]

today i spent a couple more hours trying to set the timing using a VOM. I put the motor back together again and still nothing fires. I still have spark however. Checked the plugs again and noticed they were still dry. unplugged the plug wires and pulled the starter rope and then rechecked the plugs and they were still dry. tried spraying starter fluid in the carburator but it still wouldn't fire.
tomorrow I thought i would take the carb off a second time and go thru and clean the carb again. where are the reeds located and how does a person check to see if stuck reeds would be causing this problem.
i'm hoping i can found something in the carb that is causing my problem.
still looking for ideas from any of you guys out there in the iboats community. thanks to you who have replied so far.

It should fire a bit on starter fluid, go easy on that stuff as if its got no two stroke oil in it it will burn the motor up.
Try holding a dollar note in front of the carb and turning the motor over, you may need to tape it there unless you have a helper.
The dollar bill should get drawn into the vacuum in the carb throat, (dont let it get sucked in), If it doesnt it indicates stuck reeds as you say or bad crankcase vacuum, bad seals cause that


if it gets blown out of the carb it indicates the reeds are stuck open or broken

 

[F_R]

Bad seals include bad piston rings, which also cause low cylinder compression. See a pattern here?

 

[byronjacobson]

where are the reed valves located on a 76 4 hp johnson outboard? are they easy to take out and replace?

any easy test to determine if the seals are bad on this motor?

right now i'm getting ready to clean the carb a second time to see if i missed anythng the first time.

 

[Bosunsmate]

where are the reed valves located on a 76 4 hp johnson outboard? are they easy to take out and replace?

any easy test to determine if the seals are bad on this motor?

right now i'm getting ready to clean the carb a second time to see if i missed anythng the first time.

seals is the dollar note test
reedvalves are in the inlet manifold of course

 

[byronjacobson]

Today i finally had some success. I took the carburater off for the 2nd time and let it soak in some carb cleaner. While the carb was soaking I thought i would check out the reed valves. I've never taken the reeds off a 2 stroke motor. It came out fairly simple as it was just held by 4 bolts where the carb mounts to the motor. two of the reed valves appeared to have some material stuck between the reed and the base it seals against. I removed the two obstructions, put the reed valves assembly back on the motor, put together the carb again, and finally it started and ran fairly well.
I'm not positive the problem was with the reed valves, because it could be the soaking of the carb in the carb cleaner might have fixed some unknown problem as well. I'm guessing it was the reed valve obstruction.
Plan on rechecking the compression to see if there is any change. glad i finally got it running after spending around 8 to 10 hours on this project. i leanrned a lot however trying different solutions.
thanks to all of you who posted and offered suggestions.