1959 Johnson 50 hp v4 magneto/spark issue

[ok dear]

Hello,


1959 Johnson 50 hp v4

I picked up a fast-tach wireless tachometer. Handy gadget. Point it at a plug wire and it reads rpms. Plug wires 1 and 3 read 800 rpm when wires 2 and 4 read 1,600 rpm. There are new plug wires, plugs, points, and condenser. The points are set by meter at the marks. Any ideas?
Thanks

Steve

 

[boobie]

Re: 1959 Johnson 50 hp v4 magneto/spark issue

How's the mtr run at idle and wot ??

 

[ok dear]

Re: 1959 Johnson 50 hp v4 magneto/spark issue

weeks ago it ran perfect at idle and at maybe 70%. Above 70% or so it would cut out. So I ordered the tach thinking it would help set the jets. Next time out was similar at first, then slowly got worse. Compression is within a couple of points near 80. Now, in a small test tank it will idle almost smoothly, but a miss or cut out is apparent. The odd thing is that I had the magneto on my bench and installed new plug wires. Hooked all 4 plugs up in order with a wire grounded to the breaker base plate. Ran the mag with a drill and all 4 plugs fired in order without missing. Pointed the tach at each plug wire and all read the same. Put the mag back on the motor and got the readings where 1 and 3 are getting spark signal half as much as 2 and 4, which is why I had it off in the first place. It is an hour trip one way to put this to a test in a lake, and so far nothing I have tried has had an effect.

Steve

 

[ok dear]

Re: 1959 Johnson 50 hp v4 magneto/spark issue

Update.
Disconnected drive belt and kill wire from mag. Unhooked plug wires from plugs. Ran mag with drill and all 4 wires had same spark reading as each other. Reconnected everything but kill switch (thinking maybe some kind of short). Started it up and right plug wires once again read half the reading as the left plug wires. Starts right up and runs, but there is an intermittent miss or cut out at higher rpms. It is present, but not as noticeable at idle. Responds well to throttle and sync is set by the book. I put the wireless tach right on the plug wire at the plug facing away from other plugs.
When run at the bench, all plugs had good spark at at least 3/8" from ground. But I know when I take it back to the lake the miss or cutout will have a huge effect except at idle or just above.

 

[boobie]

Re: 1959 Johnson 50 hp v4 magneto/spark issue

Are the breaker points good and clean and set properly ??

 

[ok dear]

Re: 1959 Johnson 50 hp v4 magneto/spark issue

Points are in very good condition, with maybe 10 running hours. Whole breaker plate area very clean. Points are set by ohm meter exactly at the timing marks. New condenser. sync and timing set by the book.

 

[ok dear]

Re: 1959 Johnson 50 hp v4 magneto/spark issue

update 2. Took the mag apart again. Took out the coil, which appeared fine, but there is evidence of it shorting to the mag housing at the lower left side ahead of the wires. No evidence on the coil, but I sprayed several coats of liquid rubber on it and will try some home made gasket material spacers on either side of the coil. I also put 2 layers of gasket material in the rotor so that it can't short to the shaft. This may be it! Will find out tomorrow.

 

[ok dear]

Re: 1959 Johnson 50 hp v4 magneto/spark issue

Didn't work. Engine starts fine and runs with intermittent cut out or miss. Plug wire tach reading still twice as high on the left bank than the right bank when on the motor. All read the same when off. Even unplugged the big cable from engine while running and no difference. Switched breaker point positions with no change. Seems to me that if 2 cylinders were getting half as much spark as the other 2 it would have a more profound effect than an intermittent miss or cutout. Now am wondering if there is some issue with the fast tach tachometer itself, and the intermittent miss is caused by something else, maybe fuel related. Sure seems odd though that off the motor all 4 wires read the same, but on the motor the left bank reads twice as many firings as the right. I am posting these updates so that if someone else has a similar issue down the road this info may help.

unusual points issue. I have set the points to break exactly at the marks. When I check with a feeler guage they both read .017 instead of .020. But if I set them at .020 they are way off of the setting marks with a meter. Why would it be stamped right on the magneto flywheel to set points at .020 when it will barely run at all if I do that?

 

[boobie]

Re: 1959 Johnson 50 hp v4 magneto/spark issue

Are there any carbon tracks in the distributor cap ??

 

[tx1961whaler]

Re: 1959 Johnson 50 hp v4 magneto/spark issue

fast tach tachometer = trash

 

[ok dear]

Re: 1959 Johnson 50 hp v4 magneto/spark issue

Well, I tried unplugging one plug while it was running and it sure ran rough, so I really think the issue is with the tach and not the motor. That is too bad really. I got the thing mainly because of a higher speed miss or cutout. I thought it would help setting the jets if that was the problem. It still cut out so I checked all 4 wires and observed the discrepancy of the tach reading the left and right cylinder rpms. Now the motor runs smooth and responds well in a trash can full of water, but it has done that before. I am at a loss here. The carbs and jets are clean. No leaks in the fuel system. Sure seems to use plenty of fuel! lol. What am I missing? What is a main reson for cutting out at higher rpms? The tach will help in setting the jets as it will read good enough to notice a rise or decline in rpms of a single plug. But even getting the jets fairly close to optimum had no effect on wot. I know it's not the best engine, but up till wot it is smooth and strong as a bull.

Thanks guys. I don't know why the fast tach would read like that, but it sure threw me off. I really don't think that the problem is with the mag now. But all the checks I did of the mag, and insulating the coil most likely helped. It sure didn't hurt, as now the mag is about as good as a 54 year old used mag will ever be! Great site. Lots of info here that would be difficult if not impossible to find elsewhere.