Mercury KE4 Piston Ring

[goldmember]

Does anyone have a proven method for installing the cylinder onto the piston on a KE4? I keep breaking piston rings. I have tried hose clamps with plastic with no luck. Do I have to buy a special ring compressor for these small pistons?

[The Boat House]

• This reply was modified 5 years, 2 months ago by The Boat House.
• This reply was modified 5 years, 2 months ago by The Boat House.
• This reply was modified 5 years, 2 months ago by The Boat House.
• This reply was modified 5 years, 2 months ago by The Boat House.
• This reply was modified 3 years, 1 month ago by The Boat House.

[green-thumbs]

Fist prepare the cylinders
Cylinder should be deglazed by ball hone and washed with detergent and water until
all traces of grit and abrasive. REALLY CLEAN

Inspect cylinder for scoring and excessive wear.

Inspect and prepare pistons by cleaning ring grooves and checking for scoring and
other damage. The anti -rotting pins in piston ring grooves should NOT be mashed
down..,,if the pins mashed down the rings will not align to install pistons in cylinder

Install piston on rods with open end down from the top bottom piston first on twins
The G clips sometimes get loose and fly when installing so wear safety glasses

Installing rings on pistons can be done with fingers …there is a tool for the purpose
which is nice but not essential and a little expensive unless a garage sale find,

Gasket between cylinder and crankcase has to be in place BEFORE you install cylinder …I like to use short screws to hold gasket in place while pistons are slipped
into cylinder , remove to allow cylinder to be fully inserted into crankcase.

Wipe oil on cylinder walls prito to installing pistons…I do with oily fingers…no tools needed.

Rings are on piston, piston is on connecting rod and connecting rod is installed on
crankshaf and gasket is in place on crankcase.

NOW the ANSWER to YOUR QUESTION,. I was having the same problem with the same
powerheadd despite several tries with different makeshit devices…NO LUCK at all.
I gave up and bought a piston ring clamp set out of a chain saw catalog…works every time as long as the above conditions and preparations are followed.
Bailey’s Inc.
item # 10429 Piston Ring Clamp Kit
as of 01/14/11 $7,95 plus $ 7.95 S&H
Bailey’s serves the chain saw trade. No idea why I got on their mailing list.

I have used them a number of times on Mercury twins from K4 thru Mark 7
As long as the pins in ring grooves are undamaged no problem easy assembly.

The important thing in all this is the rings have to be fitted to the cylinder and the
ends f rings have to be located and kept in place by the anti rotation pins.
Louis

[goldmember]

Thanks guys. I will get a set of those ring compressors. I have a few questions though

What does this mean…

“The anti -rotting pins in piston ring grooves should NOT be mashed
down..,,if the pins mashed down the rings will not align to install pistons in cylinder”

And

The important thing in all this is the rings have to be fitted to the cylinder and the
ends of rings have to be located and kept in place by the anti rotation pins.

I thought that the open ends should be 120 degrees apart but I am not aware of “anti-rotation pins”.

[green-thumbs]

When the piston is inserted into the cylinder the rings are compressed to conform to
the diameter of that cylinder….rule of thumb is end gap of about 0.008″ for a 2 inch cylinder bore. This allows for expansion due to heat of engine operation.

After cylinder is prepared you fit the rings by inserting the ring into the cylinder it will
be used in and measuring end gap with a feeler gauge. New rings will be over size
and used cylinders will be larger due to wear. I like to use bottom of a junk piston
to set the ring square in the bore. Fee;er gage is an inexpensive tool consisting to
a range of thin metal leaves each marked to indicate thickness. When ring is in cylinder , the thickest leaf that fits between ends of ring is the gap.
If gap is less than required, remove ring from cylinder and file ends a little and
return ring to cylinder for recheck. Rings are made from cast iron and require
careful handling to avoid breakage. A simple holding device can be made from
two thin pieces of wood and a small vise….clamp ring between the two piece of wood with just the tips of ends exposed and gently file each tip a little. Check
ring in cylinder and repeat as needed to get the right gap
Cylinder wear is uneven with the most wear in middle and least wear at top and
bottom. A ring’s end gap will vary depending on where it is located in the cylinder
You can verify if cylinder by measuring end gap at several points in piston travel
in cylinder.
For present purposes set end gap for bottom of cylinder which will be least worn spot in cylinder.
Each ring has to be fitted to cylinder it will be used in.

2 cycle engines have ports in cylinder walls. If a ring should happen to rotate around piston in ring groove, the end of the ring will snag in a port and break off
SO two cycle pistons have some device to locate ends of rings. On the Mark 7 pistons it is a round piece of copper in piston that intercepts each ring groove so the end of rings are located on piston away from ports
Mercury Service Manual procedure calls for removing rings before removing piston
from rod AND installing rings after piston is installed on rods.
I found out the hard way why.
The rings will float freely in ring grooves…removing piston pin may involve some force (of U shaped Merury Service Tool) In either case if the rings may crush the soft copper pins. That will be a problem when you put engine back together. The mashed down copper pins may not stick up enough to reliably keep the rings in,e their proper place….ESPECIALLY if you need to rotate cylinder to line it up with crankcase. If a ring is riding on the anti rotation pins, ring is pressed tightly against
cylinder wall and crankshaft will turn over very stiffly.

Good used pistons are getting harder to find. Take very good care of them or you may have to go looking for them . I hope I do not sound like and old scold or a know it all…I am still learning.
Louis
The may be some way to undo damage to piston ring pins so don’t toss otherwise good pistons.

[goldmember]

Okay now that makes sense. It’s probably the reason I keep breaking rings. Luckily my ring pins are still fully intact. Once I get my new rings I will make sure they are all aligned with the pins and use a 2 stroke plastic pin compressor.

My cylinder walls are in great shape but the pistons have some carbon scoring I can’t get off. Any suggestions?

[A Hoskins]

A tip of the hat to green-thumbs for the Bailey’s link. Their little ring compressor isn’t $8 any more but is still reasonably priced and will handle up to 60mm which is about 2-3/8″.

"Fox News" isn't.

[goldmember]

Just got these. They do work great. Thanks for the tip!

[jeff-register]

Before Louis found these ring compressors I took a 1/2″ PVC pipe, cut a 1″ piece off, then cut into quarters. Face radi towards piston ring & compress on the piston. Only advantage here is a guy can see if the ends of the ring are placed correctly on the guide pins. Use a zip tie to compress the ring & cut off after piston install.
For everyone who can’t wait for the mail.

[Author]

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