Cylinder Gouge

[Steve146]

1996 GS500 with 20K miles.  This mark in the cylinder has shown up for the second time after about 1000 miles on a replaced cylinder.  The older cylinder showed the same problem.  The connecting rod side play is less than 0.01 in.

I'm not sure what's causing it. 

[sledge]

Little-end bearing worn oval maybe?

[KasbeKZ]

doesn't look completely unlike the result of detonation. what shape is the piston in?

[Steve146]

doesn't look completely unlike the result of detonation. what shape is the piston in?

The third ring (oil ring) and it's groove are deformed and it looks like that's doing the damage.

[The Buddha]

It is in the front, You may have some binding in the pin/rod because as the crank turns at the top of the stroke it looks like it throws the piston forward instead of smoothly changing direction.
Cool.
Buddha.

[KasbeKZ]

so you think that's the skirt making that dent?

[Steve146]

doesn't look completely unlike the result of detonation. what shape is the piston in?

The third ring (oil ring) and it's groove are deformed and it looks like that's doing the damage.

Well, now that I think about it, we did change the air filter to the K&N pods and didn't rejet.  I don't hear any detonation, but that doesn't mean anything.

Little-end bearing worn oval maybe?

Although it doesn't feel bad, we didn't change the small end bearing when we changed the piston, which in retrospect, seems like a bad idea.


It is in the front, You may have some binding in the pin/rod because as the crank turns at the top of the stroke it looks like it throws the piston forward instead of smoothly changing direction.

It feels OK, but under a load that could change.


What I'm going to try is, bore the cylinder, to .5 mm, oversize piston and check the jetting very closely.

[werase643]

if you got it apart check the piston pin and little brg clearances with a mic also
it's free

[GeeP]

Let's see some non-blurry pics...

Pics of the piston too, showing the location that's been doing the damage.

Did the scraper rings and spacer come out in one piece, or were they broken?