| Author | Message | ||
     Essmjay |
What do you think? Rear piston from Macy's 2002 s3.  (Message edited by essmjay on March 23, 2011) | ||
| M2typhoon |
HOSED!!! | ||
| Skntpig |
Time to go a bit over bore and bore the walls to match. | ||
| Firemanjim |
OUCH! | ||
| Essmjay |
I already have new pistons and cylinders on order. I was wondering if anyone had any ideas on what can cause that? And I am really glad I went into the top end, no need for my wife to be riding around with that grenade under her. | ||
| Essmjay |
So... no one has any ideas on what can cause a piston to crack like this? | ||
| Preybird1 |
I could only guess? flawed from the start....Or pre-detonation?? | ||
| Willydac50 |
I don't believe detonation would cause damage like that. It could crater a piston dome or break ring lands. I would inspect my crank and crankcase really carefully because it looks as though it struck something. Of course this is pure speculation on my part because I am looking at just the bottom of the piston. I would need to get a better look at the cylinder, crank, rods and on and on before I could really make a guess. It really does look like it was struck by something, but it is just one piece of the puzzle.  | ||
| Blake |
From the length of that crack, it may be due to fatigue cracking. Detonation could exacerbate that. Is that the OEM piston? (Message edited by blake on March 27, 2011) | ||
| Essmjay |
From the gaskets that were on the top end I would say yes, I believe it is the original oem thunderstorm piston. | ||
| Bluzm2 |
Might want to ping Pammy on this. My initial thought was detonation but you don't have any indications on the crown or the ring lands.. Odd.. Brad | ||
| Fast1075 |
The joys of large bore pistons with virtually no skirt...wear pattern looks like it was rocking in the bore (could tell more if we could see the ring land area)...looks like rocking caused the crack to me. | ||
| Essmjay |
Here are more photos showing both side and inside of the piston, and inside the matching cylinder.     | ||
| Willydac50 |
That is one crispy critter! Is that the original piston? You know, we can look at these and guess all we want, but myself, I've seen dropped valves, and toasted oil pump drive gears (and all kinds of strange "shade tree mech" stuff), but I don't hear a lot of cracked piston anecdotes. I'd sooner have it and the cylinder in my hands and a bore gauge and some mics to guess any further. Looks like the motor has been running fat or being lugged or or or..... It's really difficult to make a diagnosis on something like this even with the fine photo's (and I am not being facetious). How many miles? If anyone else had more than a little anecdotal evidence that the engines were prone to this we would have heard from them by now. I think. | ||
| Essmjay |
Well, when we picked up the bike last summer it had some 7000 miles on it. Bought it from a used bike dealer, not the previous owner, so I have no idea how it was used. It was running so good I almost didn't take it down for the needed gasket replacement. I am really glad I did now. It was always obvious to me that the base gasket had been leaking for a long time from the stains on the primary cover. Thanks for all the ideas. I am guessing a full throttle junkie who didn't ever let the bike warm up first. | ||
| Pkforbes87 |
Cracked piston:   Perfect time for you to upgrade to a 1250 kit  | ||
| Willydac50 |
Now that is really fried !! I don't even _want_ to know how that happened!  | ||
| Natexlh1000 |
Hey, at least the rings kept most of the bits in one place, right? | ||
| Rick_a |
That is a sure sign of sh*t happening. I killed a top end with about 15K, then with only 7500 killed another that used fancy H-D Screamin' chicken parts with bored-over stock jugs (my crank went bad, too, which helped f-up the pistons). Go 1250 kit with Nikasil cylinders. It is the way. It runs cooler, smoother, is less noisy, and starts much easier when cold. |
