Mark 55 very close to starting!

Frustrating lack of spark on my newly accquired 1958 Mark 55. New plugs, wires and condenser(the cheap stuff). The magneto is producing a secondary voltage of around 250VAC while cranking. I would not have guessed it possible but this is actually enough volts to jump the gap on the plugs(I made a test rig with a drill motor). The spark is blue, but I cannot otherwise quantify the intensity. I just have not seen many sparkplugs going off before, what can i say.

With the cap and rotor removed I took a wire out from the high voltage tab, and jumped it to each one of the 4 points in the cap while cranking the shaft. Bingo bango. Each of them sparked solid. At first I thought, oh wow theres a spark! Then I got to inspecting and cleaning the cap and rotor thinking this is surely the entire problem, but everything in there looks good. The rotor has no resistance thru it. The cap has no resistance from the stud to the carbon button brush, which moves in and out freely. There are no cracks or signs of tracks. The gasket is sound. The points are flat and shiny.

I am no expert in setting charge/discharge points in these things, but I took them out and cleaned them when i put in the new condenser, because they looked green and black. Now they are shiny silver and clean, and when I set the distance I made them to be fully open when the high point on the cam rubs the arm, and fully closed on the flat part.
I also read something about E-Gap and rotor demagnetization, and this must be tuned as well for optimum spark, but for now I could really use the motivational boost that comes with a running motor, and save the fine tuning for later. I have seen the sparks! I can taste it! Is it just a weak coil, or will I put one in and find I need a new rotor and cap, or will I do all of this only to end up at a magneto repair shop spending money to get the thing tuned?

Any old-timers out there hip to the internet?
Thanks.

Re: Mark 55 very close to starting!

Wolcome to Iboats.

What did you set the point gap at?

Has a cmpression test been done?

Re: Mark 55 very close to starting!

Those 4-cylinder mags should pop a 1/2-inch spark with the following test:

Remove cover, cap and rotor. Set the mag body against a bench vice (or other large metal object) and move the mag so that the copper coil tab is about 1/2-inch away from the vice. Spin the mag over in the direction of operation (clockwise looking down). Should make the jump. If it does that and you don't have good spark at the plugs when reassembled, then the problem lies in the cap/rotor.

- Scott

Re: Mark 55 very close to starting!

Changed the gap on the points and now i get spark strong enough to get to the plugs. All back together now but only get it started in full throttle, and not even like that all the time. Pretty sure the timing is correct, but other than cleaning the carbs up good i don't know what else to do.

Re: Mark 55 very close to starting!

Definitely clean the carbs. Starting at full throttle only points to the low speed side being gummed up...
- Scott