78 115 Johnson 2 dead cylinders 1&2

[Tjbiggun]

I have two dead cylinders, they both have compression and Fire . I pulled the carburetor cleaned it put it back on. getting fuel plugs or wet both cylinders have weak fire I pulled the plug wire while it was running neither one of them Shock Me but I can see spark, the other two cylinders Shock Me big time I can't even hold the wire.

 

[joereeves]

Remove "all" spark plugs & do a spark test. The spark must jump a 7/16" air gap. Does it?

Plugs still removed... do a compression check. What is the psi reading of all individual cylinders?

Standing in back of the engine, facing the spark plugs, the cylinders are numbered:

2....1
4....3

Are you sure that the cylinders that have weak spark are #1 & #2 ?

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(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:

..........X1..........X2

.................X..(grd)

..........X3..........X4

This can obviously be modified to a 6 or 8 cylinder setup tester.
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