Installing piston rings, help!

 

Okay, this is probably a really dumb question because I have never done
this before...but I was trying to install piston rings today on my
Yamaha DT80 and a few things happened:

First off, The two new rings I got were not the same (one was greenish
and slightly rough and one was metallic). What is the difference? Does
it matter where they go? Secondly, I tried to install the cylinder over
the piston and it cracked both rings because they *seemed* to be too
large, even though my rings were standard size. Any suggestions? These
were OEM rings.

Thanks!

 

Maybe this will help:
http://www.scooterhelp.com/tips/engine/lam.piston.install.html

B~

 


    It does matter where they go..... in fact, follow the way the old ones
are in....and keep in mind that the open end of the ring must never line up
with each other when putting them in.... there shold be instructions in the
box they cam i to tell you just how its done....I believe the metallic one
goes on the bottom.. it is a different thickness too if memory serves me
correct and should only fit in one place.....when you tried to fit the
cylinder over the rings, did you compress the rings??  or did you just slide
the cylinder over the rings??

Hope this helps..

Fwed

 


Masospaghetti wrote:


It's absolutely mandatory to know whether your cylinder has a steel
liner or if it has a chrome plated (Nikasil, for example) aluminum
cylinder bore...

You can use chrome rings on steel cylinder cylinders, but chrome plated
liners need cast iron rings. Chrome rings will rip the chrome plating
right out of an aluminum cylinder. Don't ask how I know that...

The chrome rings are shiny, the cast iron rings are dull colored. If
the engine designer specified a chrome ring and a cast iron ring for
use in a cylinder with a steel liner, the chrome ring would be the top
ring...


Yamaha and Suzuki cylinders will have a tapered chamfer at the bottom
of the cylinder spigot that goes into the crankcase. The chamfer helps
to guide the rings into the cylinder smoothly. Before
attempting to slide the cylinder over the rings, be sure that the rings
aren't sticking out over their locating pins. The locating pins are
there to keep the rings from rotating. Every time the piston goes up
and down, the rings will expand out into the exhaust port a little bit.
That's what makes the ring clashing sound you hear from a 2-stroke. If
the pins weren't there to stop the rings from rotating in their
grooves, eventually the end of one of the rings would get caught in the
exhaust port and break, possibly ruining the cylinder...

Once you have the rings positioned correctly and the cylinder's chamfer
almost touching the top ring, you can slightly compress the piston
rings in their grooves with your fingers, or with a small screwdriver
and slide the cylinder over the rings carefully. This has worked for me
95% of the time...

Another trick that can be used on multi-cylinder bikes where you don't
have enough fingers or screwdrivers or hands to compress two sets of
rings at the same time is to use a waterhose clamp. One of the flat
metal kind, not the round wire type. You install the clamp over the
rings and tighten the screw just enough so the clamp can slide toward
the crankcase as you push the cylinder over the rings...

Then you can unscrew the clamp and remove it before sliding the
cylinder down the rest of the way...

 

one further thing, BEFORE you install the rings on a piston, check them
one-by-one in the bore to measure the ring gap.
it's generally about .003" per inch of bore diameter.
air cooled engines can be a bit less.
this detects oversize rings (as well as undersize).
also, the previous poster's comments were very good.
sammmm