'83 johnson, fuel not reaching cylinder

[jacodema]

Hey everybody, long time reader

Here's an interesting one. 1983 50hp johnson 2-stroke 2 cylinder. Had it out for fishing opener this year and worked great. I was boating over to the landing to trailer it, i had it at full throttle for about 5 minutes waiting for the trailer to show up and it suddenly died. Went from full throttle, to not working immediately. No loud noises, no mysterious blue smoke, still plenty of fuel and plenty of battery. Had my trolling motor limp me the rest of the way and on the trailer it went.

Problem: Will not start no matter how much starting fluid, fuel in the carb throat, or turns I try. Will not try to fire, will not fire at all.

Problem: Fuel will not feed into top cylinder, spark plug consistently dry

Here's what I have found:

• Top carburetor was cracked in half
  • one of the nuts attaching it to the motor backed out and caused the carburetor to rattle a little bit, and the carburetor actually split in half.
• Replacement carburetor installed, cleaned, float leveled, and gaskets inspected.
  • re-built bottom carb as well
• Fuel lines, fuel pump all working properly
  • fuel is getting to bowls and filling them, no apparent air leaks
  • bottom cylinder pulling fuel well, consistently wet spark plug
• Good spark
  • blue, hot spark in both cylinders
  • replaced spark plugs just in case
• Flywheel key still intact, timing should still be ok
• Reeds (top and bottom) look great and appear to be sealing properly
• Compression test:
  • top cylinder: 90-100 psi, takes 3-5 strokes to get up to pressure
  • bottom cylinder: consistently 120ish psi, 2 strokes and pressurized

What I haven't tried:

• Inspecting head or water gaskets
• Inspecting piston rings

I don't have a blown rod as far as I can tell, I have enough compression to run the motor though not an ideal amount. So why am I not getting fuel to draw into the top cylinder? And why won't it attempt to sputter even with starting fluid or fuel in the carb throat? Obviously i'm worried about metal fragments in the cylinder, but I would think that would cause less compression and wouldn't explain the fuel problem?

 

[racerone]

Compression should be around 140 +-----Myself I would not hesitate to remove cylinder head to inspect cylinder walls.-----Does spark jump a gap of 7/16" on a test device , yes or no ?----How did you check the flywheel key ?-----Did you remove flywheel ?----Check timing pointer for top cylinder ?

 

[jimmbo]

Ease up with the starting Fluid, that stuff is very good at stripping the Oil off the Internals that require it.
You say it has spark. Have you tried spraying a bit of Premix into the carbs to see if it fires?
The Compression Numbers are low, try another gauge.
1983. I will assume you are adding Oil to the Gas.
If it had blown a Rod, you would have heard it.

 

[jacodema]

Compression should be around 140 +-----Myself I would not hesitate to remove cylinder head to inspect cylinder walls.-----Does spark jump a gap of 7/16" on a test device , yes or no ?----How did you check the flywheel key ?-----Did you remove flywheel ?----Check timing pointer for top cylinder ?

Im sorry i meant woodruff key. I did not pull the flywheel because electricity doesn't seem to be the problem here.
Good spark gapped at 7/16”
Cylinders look smooth and not scored or anything. Bottom piston head has even carbon but top piston head has uneven carbon. Could it be the valves? I haven't cracked the valve cover.

Top


Bottom

 

[jimmbo]

Im sorry i meant woodruff key. I did not pull the flywheel because electricity doesn't seem to be the problem here.
Good spark gapped at 7/16”
Cylinders look smooth and not scored or anything. Bottom piston head has even carbon but top piston head has uneven carbon. Could it be the valves? I haven't cracked the valve cover.

Top
View attachment 362697

I don't know what you consider Scored...
Valves?
Valve Cover?

 

[racerone]

They are scored.----Motor has to come apart !!-----Reed valves have nothing to do with this issue either.-----Looks like some metal bits were bouncing around in the top cylinder too.----Take this motor apart now.----Keep running it and all hope for repair is gone.