What causes a piston to break?

[DaddyLoafin]

Outside of making contact with the rave valve what causes this to happen?

 

[etemplet]

That's not "broke." This is Broke. I'm not a piston reader but generally pistons do such things when the engine runs lean. The top of the piston melts.

 

[DaddyLoafin]

Lol yeah that’s a lot worse than mine. Does my engine need a full rebuild because of this or am I able to get away with just a top end?

 

[darren shumbo]

Lean condition due to crank seals or plugged up arbs or just leaned out too far….yes you need a total rebuild or it will happen again…cheap oil and 87 octane fuel will allow this to happen as well.

 

[DaddyLoafin]

I know the fuel line for the accelerator pump popped off that cylinder a while ago but I didn’t run it long because something was obviously wrong with it and I was messing with the carbs not long before that happened. I thought you were supposed to run 87 in these and I use quicksilver synthetic( the purple one)

 

[etemplet]

I know the fuel line for the accelerator pump popped off that cylinder a while ago but I didn’t run it long because something was obviously wrong with it and I was messing with the carbs not long before that happened. I thought you were supposed to run 87 in these and I use quicksilver synthetic( the purple one)

check your PM.

 

[Poormanracing]

If you ran it long enough to notice a problem than you rode it long enough to cause a problem.a problem cause instant damage.

 

[etemplet]

If you ran it long enough to notice a problem than you rode it long enough to cause a problem.a problem cause instant damage.

You definitely have a point. I went riding with a guy that said his ski ran 56mph. While riding my 55mph XP walked right on by his. I figured something was amiss but I didn't know him very well as we were riding with a mutual friend. I didn't say anything but skis don't low down for no reason.

The 3 of us went riding again a few months later. On the way back I caught up with him he is doing about 35mph wide open and the ski had already killed once. We get back to the launch and I pull the plugs. His PTO spark plug had grey metal all over it. Engine was toast. The first indication of a problem was he couldn't get his normal top speed. He continued riding it and did nothing about it.

So true that when your engine runs differently it's time to take a hard look or it will only get worse and cost more. I'd have pulled the carbs when it slowed down. That was the problem. Accelerator pump on the PTO carb was plugged solid among other issues.

 

[DaddyLoafin]

Well when the fuel line for the accelerator pump came off it was immediately clear somthing wasn’t right when it would start fine out of the water but was very hard to start in the water. I had check compression while I was at it and that cylinder had 145 psi. When it broke I was riding down river in the shipping channel at 3/4-full throttle and it just shut down. Started up again immediately so I went to shore and checked it and everything seemed fine. Went and rode for another 10 minutes and was heading back and it shut off again and when I tried to restart it was obviously turning over much faster than normal and it did fire back up but obviously on 1 cylinder. Luckily I was right near my dock.

 

[mikidymac]

87 octane will not cause this, they are designed to run on 87 octane.

 

[Boyd12]

You definitely have a point. I went riding with a guy that said his ski ran 56mph. While riding my 55mph XP walked right on by his. I figured something was amiss but I didn't know him very well as we were riding with a mutual friend. I didn't say anything but skis don't low down for no reason.

The 3 of us went riding again a few months later. On the way back I caught up with him he is doing about 35mph wide open and the ski had already killed once. We get back to the launch and I pull the plugs. His PTO spark plug had grey metal all over it. Engine was toast. The first indication of a problem was he couldn't get his normal top speed. He continued riding it and did nothing about it.

So true that when your engine runs differently it's time to take a hard look or it will only get worse and cost more. I'd have pulled the carbs when it slowed down. That was the problem. Accelerator pump on the PTO carb was plugged solid among other issues.

If you run an engine with a problem long enough, it will diagnose itself. The problem is that it goes from rebuildable to recyclable.