BAD piston- Q&A- Please leave some feedback:)
#1
BAD piston- Q&A- Please leave some feedback:)
I bought a 1998 polaris Xpress 300 from an owner who ran it threw water at high speed and then the atv struggled to run for a few minutes then died and never ran after that.
After they spent a bunch of money on it changing parts they sold it to me for cheap. I took a compression and it had little. So, I tore the motor down and found the piston on the left and right primarily was scraped up and a little melted. So the piston was damaged but the cylinder didn't look too bad. It was a little ruff in a few spots, but it seemed to be from some of the melted piston head stuck to the cylinder.
What do you guys think about honing the cylinder? What do you think the chances are thats all it needs rather than being bored out ? I didn't see any pitting, like I said it seemed more like a glaze from the piston. Aslo, since I didn't own the atv when it happened it is harder for me to tell excactly why it happened. But, I did find the ot be a lot of corbization on the underside of the piston head and it filled in a few of the holes on the top sides of the piston by the rings.
ANy ideas as to why there was piston failure? I have ideas, but would like to hear more ideas from those who have had piston failure experiences or know their stuff on this topic.
The motor has one cylinder, gas is gravity fed, seperate oil tank w oil pump.
Wish I could get pictures on heres of it? Maybe I could.
Would love as much feedback as I can get.
Thank You!
KELLY
After they spent a bunch of money on it changing parts they sold it to me for cheap. I took a compression and it had little. So, I tore the motor down and found the piston on the left and right primarily was scraped up and a little melted. So the piston was damaged but the cylinder didn't look too bad. It was a little ruff in a few spots, but it seemed to be from some of the melted piston head stuck to the cylinder.
What do you guys think about honing the cylinder? What do you think the chances are thats all it needs rather than being bored out ? I didn't see any pitting, like I said it seemed more like a glaze from the piston. Aslo, since I didn't own the atv when it happened it is harder for me to tell excactly why it happened. But, I did find the ot be a lot of corbization on the underside of the piston head and it filled in a few of the holes on the top sides of the piston by the rings.
ANy ideas as to why there was piston failure? I have ideas, but would like to hear more ideas from those who have had piston failure experiences or know their stuff on this topic.
The motor has one cylinder, gas is gravity fed, seperate oil tank w oil pump.
Wish I could get pictures on heres of it? Maybe I could.
Would love as much feedback as I can get.
Thank You!
KELLY
#7
Was the piston melted above the rings by the exhaust port... that can be caused by a leanout or timing issue or too hot of plugs.
If you have to buy a new piston.... without seeing your cyl I would recommend getting a the first oversize above what you have allready and rebore it...if it is a "nikasil cyl then it isn't reborable... don't know anything about the model of your bike so I can't give you advice there. If it is scuffed below the rings on both sides then it could be from the water bath.... got pictures?? Most of my experience is with sleds.........hope this helps.
If you have to buy a new piston.... without seeing your cyl I would recommend getting a the first oversize above what you have allready and rebore it...if it is a "nikasil cyl then it isn't reborable... don't know anything about the model of your bike so I can't give you advice there. If it is scuffed below the rings on both sides then it could be from the water bath.... got pictures?? Most of my experience is with sleds.........hope this helps.
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#8
Thanks for the reply Jomax
Not above the rings, but to the rings.
I am guessing water also. Vertical scratching/scoring in about 3 diff spots on the piston. I will try to take pic.
My piston size is 74.50mm (1mm=.039'')
Was thinking of going with an over bore piston size of .010'' or .020''
Does that sound about right? Less than 1mm
Thanks for the input!!!
Kelly
Not above the rings, but to the rings.
I am guessing water also. Vertical scratching/scoring in about 3 diff spots on the piston. I will try to take pic.
My piston size is 74.50mm (1mm=.039'')
Was thinking of going with an over bore piston size of .010'' or .020''
Does that sound about right? Less than 1mm
Thanks for the input!!!
Kelly
#9
Thanks for the reply Jomax
Not above the rings, but to the rings.
I am guessing water also. Vertical scratching/scoring in about 3 diff spots on the piston. I will try to take pic.
My piston size is 74.50mm (1mm=.039'')
Was thinking of going with an over bore piston size of .010'' or .020''
Does that sound about right? Less than 1mm
Thanks for the input!!!
Kelly
Not above the rings, but to the rings.
I am guessing water also. Vertical scratching/scoring in about 3 diff spots on the piston. I will try to take pic.
My piston size is 74.50mm (1mm=.039'')
Was thinking of going with an over bore piston size of .010'' or .020''
Does that sound about right? Less than 1mm
Thanks for the input!!!
Kelly
#10
That was one other thing I did notice, the underside was kinda caked with that dark chocholate grit. I will make sure I get the mixure right when things are all put back together.
Also, thanks, I did today after work take the cylinder and piston in for that reason so I had an idea of what o/s piston to get. The piston does look to be factory.
Also, thanks, I did today after work take the cylinder and piston in for that reason so I had an idea of what o/s piston to get. The piston does look to be factory.