Elto Cub Compression

[Buster]

I just took ownership of a half horse Evinrude Elto Cub.   I ran a compression check and couldn’t get more than 25 psi.  Is that normal for these motors?  If this compression is inadequate, has anyone successfully changed rings?  What is the source of replacement rings?

Appreciate any sage advice.  I would like to get this little kicker running.  I need to get the compression right before moving on to spark or carburetor.

Buster

[lloyd]

I have several Mates and a Cub with 65-70 psi that run well.  The Cub had low compression , so I lightly honed the cylinder and replaced the rings.

[Buster]

Lloyd,

Where did you get the replacement piston rings for the Cub?

Buster

[Tubs]

If that is an accurate compression reading I wouldn’t be
surprised if the rings are missing. You can get rings from
Otto gas engine works.
http://www.ringspacers.com/ringcost.htm
Once these get so worn they don’t have enough compression
to run there is only a slim chance that just replacing the rings
will get them to run again. Last time I bought rings they were
$5.00 + $.50 shipping each so for only $11.00 its worth a shot in
my option.
Tubs.

A "Boathouse Repair" is one that done without having tools or the skills to do it properly.

[Buster]

The Boat House,

Why would you say that replacing the rings might not restore compression?  Are you suspecting too much wear on the cylinder walls?   Perhaps wear in the ring grooves?

Buster

[Tubs]

Several thing are against you.
1- The cylinder will wear more at the top than
the bottom. In this Cub cylinder the end gap is
.013 at the bottom and .025 at the top. If the
end gap of a new ring is .003, in this example
it will be .015 at the top. While this may not
have a noticeable effect an a larger motor it
becomes more of an issue as the bore size
decreases.
2- The cylinder is also likely out of round some.
A new, perfectly round ring, in a not so round
cylinder also will result in some compression
loss. A light honing wont correct this.
3- Because the cylinder is worn the piston is
loose in the bore. It can tend to rock at
ignition causing the rings to be cocked instead
of square on the cylinder wall. Honing the
cylinder only aggravates this issue as it
results in the piston becoming even looser.
4- Experience – Video.
There is more but for $11.00 its worth a try IMO.
Tubs.

https://youtu.be/qJ9VhC7mnEo

A "Boathouse Repair" is one that done without having tools or the skills to do it properly.

[Buster]

Boat House,

I disassembled the cylinder today.  Using the top (existing) compression ring, the ring gap is 0.008″ at the bottom of the cylinder bore and 0.030″ at the top.  I don’t know how much of this is attributable to ring wear and how much is cylinder wear.  I’m willing to spend $11 on two new compression rings and see where this gets me.  I get only about 25 psi now on a compression check.  From this forum, it looks like I’d need 50-60 psi to have a chance on this engine running.

We’ll see where this goes.  If compression comes up with new rings, I’ll tackle the ignition system.  Otherwise, this motor is a wall display.

Thanks for the advice.

Buster

[Tubs]

The original gap would have been .003 to .004.
Your measurement at the bottom of the cyl. where
there isn’t any ware shows about .002 worn
off the ring increasing the end gap by .004 to .008.
Your measurements also shows a taper of .022.
That’s a lot. If parts were available you would
hope to straighten the cyl. by boring it to .030 over.
Then with oversized rings and piston it would
run for sure.
I still think it’s worth trying and hope it works out for
you. I find both the ½ & 1 hp. motors fun to run
but the Pal is the first motor I ever ran so I may
be showing some favoritism here. Let us know
how it comes out.
Tubs.

A "Boathouse Repair" is one that done without having tools or the skills to do it properly.

[Buster]

I replaced the piston rings today.  Compression now reads 50 psi.  That’s 100% improvement over what I had but still may not be enough to get this engine to run.   The rest of the internal parts looked good.  I’ll next tackle the ignition system.  Any suggestions where I might find points, coil and condenser?   As an optimist, I’m also looking for the correct gasoline/oil mix ratio.  Also, any recommendations on foot grease?   I’ve got the OMC HI VIS lube which works on almost everything else.

Thanks for the advice.  I’m determined to get this little kicker running again.  It belonged to my late uncle, but has been stored in the attic the last 50 years.

Buster

[Tubs]

Points- You clean and use what you have.
Oil- a lot. Fill in the spaces of the missing metal.
Gear oil- John Deere Corn Head Grease or Lubriplate 105
Search You Tube for 1939-41 Cub Mate Coil Substitute
only use the 2 cyl. military surplus coil and ground out
one spark plug lead.
I have limited internet access just now.
Can provide a better response in a few days.
Tubs.

A "Boathouse Repair" is one that done without having tools or the skills to do it properly.

[Author]

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