Hi All,
I'm having a problem with a "new to me" 1956 Evinrude 5.5 Fisherman.
The top cylinder is dry while the lower cylinder floods with gas (after 10-12 tries). This doesn't look like a new problem as the upper spark plug has something that looks like rust on the threads and the spark gap. The upper spark plug hole has had a new thread insert put into it. The lower one is well lubricated with gas and oil.
I checked the reed valves and they seem to be free and working.
I did a compression test for the cylinders and the top one is around 35# while the bottom one is around 87#. I stripped the head down and removed the top piston.
The head gasket seems to be in good condition and there seemed to be no air leaks when the plugs were in and I turned the flywheel.
The rings seem to be OK, they're not seized, cracked or rounded. The inside of the cylinder walls are smooth but not pitted and could stand a honing. The only thing I noticed was the piston has a score mark on the skirt about 1-1/4" long, 3/16" wide and a few thousands deep right about where the piston would pass the exhaust ports. The surface is rough and you can feel raised pieces of metal. There are no chips, burrs or metal debris in or around the exhaust ports.
Could this skirt be the problem with the compression? I don't know that much about 2 strokes but the damage is between the rings and the piston rod. Isn't the suction to draw fuel and the compression for firing done between the rings and the spark plug? That would be the opposite end.
I figure the lack of compression would equal a lack of suction and that is why the upper cylinder is dry.
Any help or insights would be appreciated.
Sorry if this appears twice, I was having a problem with the login.
Thanks,
Frank
I'm having a problem with a "new to me" 1956 Evinrude 5.5 Fisherman.
The top cylinder is dry while the lower cylinder floods with gas (after 10-12 tries). This doesn't look like a new problem as the upper spark plug has something that looks like rust on the threads and the spark gap. The upper spark plug hole has had a new thread insert put into it. The lower one is well lubricated with gas and oil.
I checked the reed valves and they seem to be free and working.
I did a compression test for the cylinders and the top one is around 35# while the bottom one is around 87#. I stripped the head down and removed the top piston.
The head gasket seems to be in good condition and there seemed to be no air leaks when the plugs were in and I turned the flywheel.
The rings seem to be OK, they're not seized, cracked or rounded. The inside of the cylinder walls are smooth but not pitted and could stand a honing. The only thing I noticed was the piston has a score mark on the skirt about 1-1/4" long, 3/16" wide and a few thousands deep right about where the piston would pass the exhaust ports. The surface is rough and you can feel raised pieces of metal. There are no chips, burrs or metal debris in or around the exhaust ports.
Could this skirt be the problem with the compression? I don't know that much about 2 strokes but the damage is between the rings and the piston rod. Isn't the suction to draw fuel and the compression for firing done between the rings and the spark plug? That would be the opposite end.
I figure the lack of compression would equal a lack of suction and that is why the upper cylinder is dry.
Any help or insights would be appreciated.
Sorry if this appears twice, I was having a problem with the login.
Thanks,
Frank