Topic: 1936 Johnson A-80 4.5 hp power head HELP! – Antique Outboard Motor Club,Inc

This topic has 22 replies, 5 voices, and was last updated 6 years, 6 months ago by squierka39.

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October 27, 2017 at 7:11 pm #8552
Buccaneer
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I started tearing down the power head on the subject motor today.
Things seem to be in pretty good shape, but did find one rod bolt
a tad loose.
I’m not able to remove the crankshaft. It slides about 3/4" and
hangs up hard. There’s no external bolt (like a Mercury) in
the center main bearing that is holding it, and I see no internal
big circ clip or such either. There does appear to be some kind
of thin bronze liner / bearing that the center main rides in.
I tried tapping on the crankshaft but did not wish to break
anything so I stopped.
Any clue what’s holding the crankshaft from coming all the way out?

Is the "valve disc" in the exhaust body a back pressure relief for starting?
It operates in conjunction with the throttle or choke on the carb, but
I didn’t try to figure out the logic before I tore it apart.

In the cylinder jug intake ports are accordion-like baffles.
Are these to help atomize the fuel, or back fire arrestors, or what?

Thanks for any clues!

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October 27, 2017 at 9:58 pm #66698
squierka39
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On the crankshaft the center area is the rotary valve, there are 2 compression rings that fit into slots in the block and compress against the crankshaft. These are the only thing that could hold it up, maybe if one of the rings got out of its slot it could catch on the intake ports in the crank, or one could be broken also catching on a port. Other than that you have the top bearing out or just unbolted and there is nothing on the bottom. Should just slide up.

The disc under the exhaust is as you guessed an exhaust relief for starting. It’s open at the correct starting position of the throttle and timer, then closed as you accelerate.

Right again, the accordion baffles are listed as anti backfire in the parts catalog.

Good luck getting the crank out, mine was the opposite, the rings were stuck loose so it came out to easy. I was able to clean the grooves out and they should be fine. I hope this helps figure it out.
October 27, 2017 at 10:00 pm #66699
squierka39
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Studying your picture again, the bottom flange is probably hitting the compression rings, they have to squeeze by. Try turning it as you pull it up and out, it will hang up on both of them. Also try some oil in that area so I slips by easier.
October 27, 2017 at 10:36 pm #66700
RICHARD A. WHITE
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Lifetime Member
Remove those accordion parts, if they break apart at any time, some of that can get lodged in the bore ruining a good motor, and if memory serves it was to prevent backfire?????

http://www.richardsoutboardtools.com
classicomctools@gmail.com
October 28, 2017 at 1:50 am #66710
Buccaneer
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Thanks for the replies. Earlier I was looking in the 3rd edition
Johnson manual. While it doesn’t show the A-80 Johnson,
it did show a "K" series power head that looked very
similar in construction.
It mentioned two compression rings on the center bearing as you mention.
I did NOT say anything special to do in order to pull out the crank shaft.
Perhaps there’s a groove worn in the center bearing from the lower
ring, and the groove is catching on the upper ring, or as you mention,
the flange by the bottom crank pin is "catching".
Will try oiling things up tomorrow, twist, tap, etc., and see if pops
free.
Wonder if some thin shim stock strips inserted over the flange would
expand the bottom ring, allowing the flange to pass by?
Hope the rings are not broke……. may not find them at Walmart 😮
Richard, I’ll inspect the "backfire baffles", and if at all deteriorated,
will remove them.Thanks!

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October 28, 2017 at 2:17 pm #66723
squierka39
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On my K80 the flanges where bunked up with built up crud, push the crank back so you see the flange and clean it up good, it wouldn’t take much to not fit by the rings. You’ll get it.
I doubt that a groove has worn in, the center isn’t a bearing so the fit is not tight. The ring should grip rotary valve and spin in groove of block.
The K series is pretty close to the A just bigger, so your manual should help you.

I’m sure your noticing a lack of responses from people. I’m not sure why but our motors are not the favorite of collectors. But, they are great running motors.
October 28, 2017 at 2:22 pm #66724
squierka39
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Oh, and the accordion anti backfire thing was discontinued by Johnson the next year. It sure seems to take up a lot of space in the intake.
October 28, 2017 at 4:01 pm #66729
Buccaneer
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US Member
Thanks once more for the tips. Sounds like I should
just take those baffles out and make the wife a
pair of earrings with them!

After gaining a little knowledge yesterday about what
I was "fighting" on removing the crankshaft, I
determined this morning that the crank flange was
indeed catching on the bottom sealing ring.
I used a wire wheel in the drill, and shined up
the flange, getting rid of any rust, and perhaps
de-burring it at the same time. Could then see
that the flange had a tiny chamfer. Oiled up
the flange, and it came out then with little
trouble.
The sealing reals were loose in their grooves,
and appeared "okay".
After I get it cleaned up, I’ll take some photos of
the crank center bearing sealing rings for
those curious.
Much appreciated!

Prepare to be boarded!
October 28, 2017 at 10:53 pm #66749
Buccaneer
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US Member
Worked on the Johnson for a couple of hours today.
Started cleaning and de-carboning ports, cylinder, etc.
Took studs out of the crankcase and cylinder head and
cleaned up and leveled the gaskets surfaces.
Took some photos for "show and tell" on the crankshaft
center rotory valve sealing system. Just two rings ride on the center
crankshaft hub. Placement of rings in crankcase and
where they ride on the crankshaft valve noted.

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October 28, 2017 at 11:23 pm #66751
squierka39
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Looking good!
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