timguy
Silver Medal Contributor
Just took a 1966 Johnson 5 horsepower in on a trade in where the guy had it "repaired" and it would not give him any power at wide open position. Before the repairman had it, he did have full power but the throttle would not stay in position because there was not enough tension apparently on the stator plate mechanism. As most of you techs must know this is a non-reversing lightweight version of the 6 horsepower. I did a compression test and it is between 65 and 70 lbs. I found that the guy had replaced coils, points, condensers, and rebuilt the carburetor. The points needed alignment and proper setting and the small donut gasket at the base of the carburetor bowl was missing. This would account for the motor running quite rich and unable to build speed, however it did idle pretty well. As you may know the five horsepower uses a smaller bore carburetor but otherwise almost the same version as the six horsepower, with the 41 main jet. After replacing the donut gasket, making sure we had a good seal, it started immediately, but still wouldn't build speed ....running rich, both cylinders at about 150 degree operating temp. By the way I had to put in a thermostat as there was none in place. Whoever put the new thermostat cover on must have thought it would run better without a thermostat....HA! It is a very low hours motor in beautiful condition. So I checked the orifice bore on the main jet thinking it was reamed out but no such luck, it is the correct bore. Next I tried a 6 hp carburetor with the larger throttle bore and also the number 41 main jet and the motor runs better but I have to put my finger partially over the choke opening before it will speed up to full throttle. Of course it will not idle now worth a damn with low speed needle set at 1 1/2 turns open with this carb.
So what's wrong? Did the guy mess with the timing? It seems to have all the original parts and throttle advance ramp. It really idled good with the 5 hp carb, but the low speed jet was completely closed. Note: no leak of fuel pump diaphragm into the crankcase.
Please help....but hey, I don't expect anyone to figure this one out on first guess.
So what's wrong? Did the guy mess with the timing? It seems to have all the original parts and throttle advance ramp. It really idled good with the 5 hp carb, but the low speed jet was completely closed. Note: no leak of fuel pump diaphragm into the crankcase.
Please help....but hey, I don't expect anyone to figure this one out on first guess.
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