Another question...pistons in general

I dunno. Is a Zebra just a striped Donkey? Enquiring minds want to
know...

I would use a piston of the correct part number intended for a specific
motorcycle before I would use aftermarket replacements or try to "mix
and match" parts intended for another model of the same displacement...

Some pistons are cast aluminum, some are forged under pressure for more
strength.

A piston *looks* basically cylindrical. But it's not. It is bigger
around at the bottom of the skirt than it is at the piston crown, and,
it's not even actually *round*, it's cam-ground with a slight oval
shape, so it will have room to expand as it gets hot.

The piston pin hole may be offset toward the rear of the piston so
piston thrust resulting from the crankshaft roration and the rod
movement will seal the exhaust port better.

The piston pin hole may be closer to the top of the piston in some
models if the engine uses the same stroke with a longer rod.

Some engines use "overhead location" to center the rod between the
crankshaft balance weights. The idea is to get rid of the shims on
either side of the rod's big end, so special spacers are installed on
either side of the rod's small end, and this means the piston has to
have its pin bosses machined specially to make room for the spacers.

Thinner piston rings will survive higher accelerations at the top and
bottom of the stroke. Thin rings flutter at much higher RPM and are
used in racing engines. Enduro and trail bike engines might use thicker
rings for longer life. So the ring grooves will be different widths.

Some pistons may use L-shaped "Dykes" rings for better sealing. The
piston crown will be machined differently.

Some engines use booster ports on the rear side of the cylinder wall to
direct airflow across the top of the piston. These pistons sometimes
have a square hole in the back of the piston.

Some pistons have trenches or troughs in the crown to direct airflow.

Some pistons use a circlip, some use wire rings, and some use helical
piston pin retainers...

There's a lot to know about piston technology. It's easier for the
uninformed to just go with the original equipment parts.

 

Hi all, another quick question for you. Whats the difference between
pistons? I am looking for a piston for my '81 kaw ke125, 56x50.6mm bore
and stroke. Can I get any piston of that bore and stroke? Ive noticed
that alot of the kaw 125 bikes of the time had the same 56x50.6mm spec
ie. kx125,ks125,ke125 can I get a piston from any of these bikes or are
there other differences other than the bore and the stroke?

Sorry if this is a dumb question, but you gotta start learning somewhere.

Thanks