what causes cylinder wall scoring? new to two strokes

[trikes4life]

my buddy just blew up his 250r. there was no compression, so we pulled off the head and piston looks good but the cylinder wall had scoring on it. what would cause this?

[oldskool83]

imm guess not running nuff oil, then metal to metal friction and worse case leading to it seized

[trikes4life]

Would not running enough oil in the crank cause this. Because we mixed the fuel and oil at 32:1.

[84atc200]

Would not running enough oil in the crank cause this. Because we mixed the fuel and oil at 32:1.

32:1 is enough, thats what i mix mine at

[Grizzlypeg]

Scoring is common, its also a matter of how bad the scoring is. Not sure what you are looking at. No compression at all you say? Does the cam open the valves?

[ShaneNP123]

a cam and valves? We are talking about a 2 stroke here

[Grizzlypeg]

a cam and valves? We are talking about a 2 stroke here

That was a pretty dumb comment of mine to make. I've got 200x timing chains and cams on my mind lately, if that's any excuse.

I wonder if he's overstating it when he says "no compression"? Got me thinking about what else could be messed up, but then I go talking apples when your discussing oranges.

[Macdiesel]

sounds to me like he ran it untill the compression completely went out... my guess the rings got so weak, sharp and bad that they cut into the cylinder, hopefully a good bore and hone will fix the scores, if not buy a new sleeve and go about your business

[MTS]

Lots of things cause scoring...Pics tell a thousand words....Could be lack of oil, Dirty air filter, cold seize.....ect..

[trikes4life]

thanks guys for the input, im new to the world of 2 strokes. I'm trying to learn as much as i can now. 2 strokes are dying breed around here lately and every body is going to 4 stroke. I'll pull the cylinder in the morning and see what I'm dealing with. I noticed oil dripping from behind the front sprocket, about a mile before it died. so i think im going to start investigating and see what went wrong.

[Grizzlypeg]

You have to watch for seals on 2 strokes. As the mixture passes through the crankcase, leaking crank seals will allow unintended air to leak in and dilute the fuel to air ratio.

[84atc200]

thanks guys for the input, im new to the world of 2 strokes. I'm trying to learn as much as i can now. 2 strokes are dying breed around here lately and every body is going to 4 stroke. I'll pull the cylinder in the morning and see what I'm dealing with. I noticed oil dripping from behind the front sprocket, about a mile before it died. so i think im going to start investigating and see what went wrong.

The oil leaking from behind the front sprocket just sounds like a bad seal.

[Glamisman]

A 2 stroke motors piston rings are pinned to the piston so that they do not rotate around the piston like a 4 stroke motor. If you look at the front and rear of the 2 stroke cylinder you will see that there are ports cut into it. If the piston rings were to rotate around the piston, the open end of the rings will catch an edge of one of the ports and tear itself apart. Having said that, if the piston gets any sort of wear on the skirts it allows the piston to rock ever so slightly and this slight rocking motion allows for the rings to catch an edge and score the cylinder. If it is an air cooled 2 stroke the problem is even worse because more piston/cylinder clearance is required because it is air cooled. A piece of reed could break off and stick in the cylinder and do damage also, fiberglass reeds are notorious for this.