Home › Forum › Ask A Member › 1940 Johnson HD-15 Magneto testing
- This topic has 37 replies, 3 voices, and was last updated 7 years, 5 months ago by Buccaneer.
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June 28, 2017 at 11:18 pm #60567
Time to give it some thought and take a break. If your like me heck I will wake up with the answer. I wonder if bakelite is off it would be nice to know for sure. From what I have read your a great mechanic with carb tuning skills. Looking at everything knowing your good at repairing outboards something is off. I can see looking at pics you have attention to detail.
Let us know when you figure it out I know you will.
Joe
June 29, 2017 at 12:24 am #60569Thanks Joe, perhaps someday I’ll stumble upon another
one of these units and can compare or switch parts.
Forgot to mention prior regarding the points cam
that it’s ground into the crankshaft, therefore it’s
not upside down!Prepare to be boarded!
June 29, 2017 at 1:19 am #60572June 29, 2017 at 2:37 am #60578If you only have one lobe, you need a magneto with two coils. If it is original and ran before, you have two lobes. If you got it apart in a box, all bets are off. . . 😆
June 29, 2017 at 2:52 am #60579HD-15 crank has two lobes ground in it, so
all is well there!Prepare to be boarded!
June 29, 2017 at 11:55 am #60585That’s good to know bakelite and tab is in correct position and you weren’t getting double fire that’s also a good thing. Something weird going on might not be ignition.
Joe
June 30, 2017 at 1:52 pm #60652I just can’t get this motor out of my mind. lol
I downloaded your video with youtube downloader and played it back slow speed several times with VLC media player.
I noticed that you have the speed lever pretty high. When I watch video motor seems to slow down then try and pick-up to high speed but just can’t make the transition to wot. It does this several times before it finally dies.
When I rebuilt my sea doo 2 stroke jet ski’s like 15 years ago they also have a rotary valve. The crankcase was suppose to be pressure tested using a leakdown test to check crankshaft seals. 2 of those seals are mounted to the center of crank and crank has to be disassembled and pressed back together to change them but you can change the outer 2 easily when rebuilding motor. Those seals are very important with a rotary valve and the case can’t leak either where it clam shells and bolts together. if they do leak you get a motor that won’t run correctly.
I wonder if when it was running if you could mist some 2 stroke fuel mix into the throat of carb and see if motor speed increases to wot or close. I have also heard people using some propane gas from an unlit propane torch. By doing this it might let you know if top and bottom seals are doing their job. I don’t know if that motor has an oil slinger on top instead of seal. It might also let you know if perhaps case might be leaking. Since you have motor back together wouldn’t be hard to check.
I also got all my electronics to build red atoms yesterday. I would be glad to mail you a couple at no charge once I build them. You could try one in that engine if it won’t work then you could put them into another 2 cylinder omc motor and see what you think about them.
I also noticed looking at the pics you didn’t put new wires from coil to brushes. Mumbles looks like he did. That one wire on the left in your picture going from the coil to brush looks pretty close to the coil laminate do you think fire could be jumping there??
Hope that helps,
JoeGetting ready to go camping this weekend happy 4th!!! to everyone
June 30, 2017 at 4:41 pm #60663Joe, the HD has been drained of fuel and put back on the
rack for now.
This 1940 Johnson has "no" crank seals. I did lap the
crankcase halves to true up the sealing surfaces, and tighten the crank
bearings on the crankshaft, normally I "no-no" I’m
guessing, but it actually made the crank bearing halves
more "round", and with less clearance. Also I installed
new rings. Compression was in the low 60’s when I checked
it originally after putting it back together.I didn’t want to take the chance of un-soldering the wires
to the coils, but I did coat the old wires with Super Corona Dope.
I seen no signs of "burn marks" or arcing anywhere on the mag
in the many times I had it apart. 🙁I like your idea of using propane. Maybe it would tell me if
the crank case halves are sealed properly.
I know that back in the day, ether worked good for checking
crankcase seals leaking on the clutch end of snowmobiles!Some day maybe I’ll take you up on the red atom modules, but
I should probably try them on a normal running engine first
to know if they’d work for me, lol.Hot and heavy into my new to me, but sad looking 52 Fleetwin.
I will not forget the little Johnson….. I hate to be defeated!
Thanks, BuccPrepare to be boarded!
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