Can you spot the oil leak?

[China_Racer_1]

Ok see how good your eyes are.. can you spot the cause of my oil leak?

[thatkid]

Yeash, that sucks

[reelrazor]

Dang Steve,

I think you overtorqued the flux capacitor

[ragedigital]

Have you found what caused that? To be honest, I was a little worried about taking a new engine and letting it scream right away at the track. It really didn't have a break-in period - did it?

darrin

[yamaha_george]

Have you found what caused that? To be honest, I was a little worried about taking a new engine and letting it scream right away at the track. It really didn't have a break-in period - did it?

darrin

More like the locals took a dis-liking to the engine with an AK

[China_Racer_1]

I have not found out what caused this yet. I plan to take the engine down later this week.

I did brake in the engine. It went trough a very methodic brake in. The new pistons also went through a lot of sessions of me babying it until I felt it was broke in enough to whack the throttle.

It ran like a frigin champ during th race the other week. man I could hardly keep the front end on the ground. Now a few weeks later it just goes Kablamm!

[shift]

what bike is that?

[China_Racer_1]

what bike is that?

Sadly is was my hybrid.

[China_Racer_1]

OK I got the engine apart and here is what I found:


The #3 piston (3rd from left if your sitting on the bike) was wedged-jammed and meshed together with the #3 cylinder.


The underside shows the result of a catastrophic failure.


The rod or parts of it busted through the case.


If you look at this debri I found in the pan you will notice a few interesting clues as to what happened.

1st the pistons cir clips wre found in the pan not on the pistons

2nd the rod where it attaches to the crank is busted hard on one side which you can see by the bolt being broken in 3 places and the rod piece broken off.

3rd one of the bolts is not only intact but I could start the threads a little on the nut

4th If you could get a good look at the engine inside and the damage to the crank you can see that basically it was debri in there moving around and busting everyhting up.

So what d I think happened? Well I think a rod bolt was not torqued or something and it backed out and got all jammed up in there and caused a catastrophc failure. Why is only based on the fact I see one bolt twisted up and one bolt that looks relatively OK.

it was an unequal event. one of the bolts had to be somewhere other than the other side of the crank. This is just an idea though and all thoughts are welcome. Maybe I am dead wrong. But its jsut what Ifigured. Anyone else got any ideas?

[yamaha_george]

Steve,
with the piston retaining clip in the pan,I would say the pin moved out& then stuckthe piston mass thus ripping out one of the bolts and then it grenaded big time.

What will tell you if my hunch is right:-
A} the bolt hole in the rod is stripped of thread on one side & not the other
B } along streak/ gouge in the cylinder wall ( probably that wedging of the pin cause the split in the case at the seam)

The other reason to find the rod pin clip is if the piston broke and the skirt came apart freeing the clip but then i would not see the bolt issue and the piston break would be more uniform around the skirt .

Most likely the pin clip came off first since this is one of the centre two pistons and they are notorious for a pig to see what you are doing & those clips in particular always seem to be in shadow. (I know that from similar experiences on other bikes )

[China_Racer_1]

George,

Really so you think the cir clips came off and got it all mucked up then. Hmm ok good feed back and you had it happen before as well you said. not good.

I was wondering how thoe two clips could both come out like that. I understand one of them flying out from the failure but both seemed a bit odd. so a good theory to think about.

I know I had a hard time getting the clips off to take off the good pistns so to have both come out and be in such good shape and form would make some sense but I think being stuck in there might cause more damage to the clips but maybe not. I will look at the insides a bit more.

[ragedigital]

While I originally agreed with the "cir clips" theory, I think it may have to do with the bolts, but we'll know more when Steve tells us what the inside of the cylinder looks like. It would have to be pretty torn up.

My bet is with a con rod bolt... either wasn't installed using Threadlock, it stripped or it was a not tightened properly. Once the bolt fell out, the con rod was pulled down below the crankshaft and the piston was allowed to travel below the cylinder base and there by creating the perfect scenario to snap the con rod in half.

[olie05]

...Once the bolt fell out, the con rod was pulled down below the crankshaft and the piston was allowed to travel below the cylinder base and there by creating the perfect scenario to snap the con rod in half.

In order for the con rod to be pulled down below the crankshaft, BOTH bolts would have to be out and missing nuts. The crankshaft can not pull the rod below the cylinder base unless the big end is off of the crank journal. Even then it seems like a stretch.

This seems like a combination of things (loose rod nuts + circlip theory). I have had a rod nut come loose on an engine before and although the rod broke in half, the piston was still free to move up and down the bore when I dismantled it.

[ragedigital]

In order for the con rod to be pulled down below the crankshaft, BOTH bolts would have to be out and missing nuts. The crankshaft can not pull the rod below the cylinder base unless the big end is off of the crank journal.

That was my assumption. I highly doubt that one bolt would be able to hold the pressure, so it would snap off, the bottom portion of the con rod would have fallen off and the bottom portion of the top con rod component would have been pulled down and pushed out of the front of the case, pulling the piston down.

Just a theory. It's really hard to tell what happened exactly.

[China_Racer_1]

Ok wel if it helps teh cylinder is smooth adn with out any defects.. except at teh bottom where the pisotn tried to make its own hole.

I think that yeah if one bolt fell off. (Note the good still somewhat functional bolt)
Then the other one could not take the pressure (Note it is sheered off in two places on place being right at the nut)
at thsi point in time it could be possible for teh whoel kit and cabudle to jstu go ape shit explode bst up and pull everything down with it.

I think after thinking on this and maybe looking at the shape of the cylinders I would say the cir clips blew of on impact of the piston to its final resting place.

Noe: one side where the cir clip should be is broken off so it simply fell out. The other one who knows.. lots of pressure and violence going on in there at that point.

As far as teh bolt coming off in the first place.. who knows why.

I do know I was there when Spyder put this part together adn he torqued everything so I am nto blaming him and I think he did nto have anything to do with this. There is so much heating and colling and stuff going on maybe I should have retourqued after engine break in. Not sure but a moot point really. its exploded and thats that.

now what to do with these cool smashed to shit piston and parts. makes for a good coversation piece on the garage shelf I guess ha ha