Topica Loopframe_Guzzi Archive


Subject: RE: Bad Piston?

Author: oger wells

Date: Apr 7, 2005, 8:09 AM

Post ID: 1718664182



The only area i see that is worn on the cylinders are on 2 spots at the
top. There is some discoloration that is less than 1/4" X 2"wide with
the ends tapered. On both cylinders they are opposite of eachother. ie 6
o'clock and 12 o'clock. I would not call it a ridge just an area that is
a little rougher and off colored. I was not the person who disassebled
the engine so i am not sure if any chrome was visisble. Crank etc look
fine.



Matt Moore wrote:
 
Oger,
is there any kind of ridge at the topof the cylinder, where the rings
stopped scraping. Run your fingernail across it. If it catches your
fingernail, then there is enough there to damage a new set of rings. If
this
were a regular iron bore (like a car/tractor engine) you would have to
use a
ridge reamer to remove the ridge. since these are chrome lined alloy, if
there is a ridge, it might be best (not cheapest tho as others have
said) to
put on a new set.
Mine had a big pile of junk in the bottom of the sump, and when I
disassembled the motor, lots of chrome flakes were embedded in the
bearing
material of the big ends and main bearings.
Have you taken the rods off the crank to see if those bearings are OK?
Might
be an idea to check that while you're there, with plasti-gage if they
look
in good shape (no scoring, grooves...)
Another way to tell if chrome has flaked off is to look at the rocker
spindles and see if there are little bits in there, and scoring of the
copper bushings. Mine also had this damage.
What I was surprised about was that with the bores as loose as they were
(.005" OVER the max service spec at the top of the bore) and as messed
up as
the bearings were, it still ran fairly well.
Now that I have rebuilt it with new pistons and Nikasil cylinders, WOW
what
a difference.

Not saying that you could not re-ring and have a great running bike,
just
thoughts.

YMMV

Good luck

Matt in MI
1973 Eldo

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