Well THERE'S your problem!

[burning1]

I finally started tearing into the siezed GS500 race bike engine, to identify the cause of the failure and determine the best course of action for repair. Was kind of hoping it was something simple...



Guess not.







Other cylinder looks a little carbed up, but otherwise fine.




I'm not sure at this point if a piston failure lead to the bottom end failure, or whether the rod or rod bearing went out, causing the pin to be torn out of the piston. Would appreciate experienced input on that.

[mister]

I'm not sure at this point if a piston failure lead to the bottom end failure, or whether the rod or rod bearing went out, causing the pin to be torn out of the piston. Would appreciate experienced input on that.

It broke. Don't try to start it up without oil 



I'm not a mechanic's son. And I can forward the pics on to my maestro mechanic for his Opinion if you like. But I would be inclined to think the rod or rod bearing went out before the piston. Rods, bearing, shafts, etc., I think, would all go first, which can then lead to other things. Though, in the scheme of things, whether the rod or bearing went before the piston the result is the same.

I've put the pics to him so we'll see what he says just by the pics.

Michael

[burning1]

In this case, knowing exactly what failed could be helpful... I have a couple of other engines that I'm planning on building up to race on, so if I could identify this as a piston or rod failure, it may be worth investing some money in aftermarket parts to help prevent this kind of failure from happening again in the future.

[slipperymongoose]

How many k's were on the bike before you turned it into a race bike? And how long was it a race bike before it failed? Yeah looks like you did a good job doing it.

[burning1]

4K miles on the bike before it got raced.

25 days or so. So, probably 3K miles of race use. High oil consumption rate on the race bike. Oil was allowed to get about a quart below minimum about 5 trackdays before the failure occurred. Noticed a slight ringing from the engine after that, but the sound wasn't exactly right for a bearing failure.

Engine seized suddenly. There was no momentary drop in performance before hand, or other indication that it was about to go.

[Janx101]

holy smoke! .. Can i vote for this as seizure of the month .. Thats a hectic breakage!

[Steel]

I don't race, but I was recently made aware that my gs consumes a lot of oil as well, when riding down the road I lost a ton of power and started hearing what I would call a ringing sound as well. Upon inspection I was a full two quarts low. Could my problem be related? Am I heading for a siezed engine?

[burning1]

Could my problem be related? Am I heading for a siezed engine?

Signs point to yes. If I were you, the first thing I'd do is pull an oil sample out of the engine, and send it in for used oil analysis. They can tell you what's in the oil, which would give a good indication of whether or not you experienced some sort of severe engine malfunction. I was planning to do this myself, but the engine went before I took a sample.

Huge number of lessons here, and I feel like a real fool for a number of the decisions I made.

[ohgood]

looks like oil got low, piston got hot, turned plastic, then wrist pin pulled through = cablooie.it's gonna be hell to flush all the mess out of that engine and transmission.

I don't race, but I was recently made aware that my gs consumes a lot of oil as well, when riding down the road I lost a ton of power and started hearing what I would call a ringing sound as well. Upon inspection I was a full two quarts low. Could my problem be related? Am I heading for a siezed engine?

the high oil consumption likely means rings. while that isn't a bad thing other than the expense and wastefullness, it could lead to a similar chain of events if/when the oil level is low enough to starve the pump.

mine would use 1/10th to 1/5th quart per ride depending on how much was high speed. normal in town riding meant little to no loss. i don't know if it has to do with the number of engine cycles or what, but the high speed stuff will definietly suck down the oil.

you could stop now, and ring your bike. i'd bet your oil consumption drops to very little. before you do that, do a compression check. and/or a leak down if the compression check shows one cylinder is crazy low. should be able to pinpoint if it's rings or intake/exhaust at least that way.

[Steel]

If I were you, the first thing I'd do is pull an oil sample out of the engine, and send it in for used oil analysis.

I may do that. Can you recommend a send away lab you've used before? Thanks for the advice!

[Paulcet]

I've read a lot of people use Blackstone Labs
http://www.blackstone-labs.com/

[noiseguy]

I don't know what caused the failure, but I'm looking at the pics of the cyilnder walls... they are awfully shiny. Not much honing left... I can't imagine you were getting a great seal with the walls looking like that. Less than 10K miles? Yeesh.

How do the cylinder heads (combustion chamber) look? Any clues?

[Phil B]

...
Engine seized suddenly. There was no momentary drop in performance before hand, or other indication that it was about to go.

owch.

So, from a rider's perspective, what's the best thing to do when you're ON the beast, and the engine seizes up like that?

[rayshon]

...
Engine seized suddenly. There was no momentary drop in performance before hand, or other indication that it was about to go.

owch.

So, from a rider's perspective, what's the best thing to do when you're ON the beast, and the engine seizes up like that?

do you guys mean sieze as in "the darn thing blew up, smoke everywhere" or the engine and wheel locking up?

[makenzie71]

That's what happens when your top end and your bottom end meet.

[Suzuki Stevo]

Looks like maybe the top of the piston decided to stay at the top of the cylinder, while the rod and wrist pin finished it's trip to the bottom? 

[slipperymongoose]

Either way you've done a good number.

[sledge]

The pot looks to have been overcome by friction and seized at TDC, probably when for that fraction of a millisecond it stopped carrying kinetic energy and become stationary prior to changing its direction of travel from up to down.

Inertia has then played its part and the mass and speed of the still moving parts including the whole bike itself have acted to keep the crank rotating. Upshot bring the now seized piston has been subject to a severe tensile load and it has failed at the weakest point, in this case directly across the little end journal where the pot contains the minimum amount of metal.......... For want of a better description the piston has been stretched and pulled apart along its axis. Secondary damage has then occurred to the cylinder and lower end as a result of loose pieces of the now broken piston

This has happened at high speed, had inertia been less at the instant the piston seized damage would have been less severe.

The question is why did the piston seize. The obvious answers being oil breakdown/starvation and/or overheating.

[burning1]

owch.

So, from a rider's perspective, what's the best thing to do when you're ON the beast, and the engine seizes up like that?

Pull in the clutch at the first sign that there's something seriously wrong for the engine, raise your hand up, and pull over to the side of the track. Most of the time, when the engine seizes it doesn't take out the transmission, so by pulling in the clutch you can maintain control of the bike until you can get somewhere safe.

In my case, it went in the middle of a corner with no warning, and put me on the ground before I knew what had happened. Bent the bike up and dislocated a shoulder in the process. I'm glad that I came out of it better than the bike did.

do you guys mean sieze as in "the darn thing blew up, smoke everywhere" or the engine and wheel locking up?

We mean seize as in, the engine suddenly stopped spinning, and the wheel locked up as a result. Engine wouldn't budge with a wrench on the signal rotor. No other obvious external signs of problems, and I had no idea how bad it was till I pulled it apart.

The pot looks to have been overcome by friction and seized at TDC, probably when for that fraction of a millisecond it stopped carrying kinetic energy and become stationary prior to changing its direction of travel from up to down.

Piston wasn't at TDC when I pulled it apart. I will knock on it with the handle end of my wooden mallet to see how hard it's wedged in there. With that said, there's not much of a skirt to keep the thing square in the bore, so there's a good chance that it'll be stuck anyway, proving... Not much.

[sledge]

My learnings and experience tells me that if a pot starts to pick up or siezes due to oil starvation or reduced clearances it is almost always at either the top or the bottom of its stroke. This I believe is due to the fact it lacks inertia at these points and consequently is far more likely to be overcome by the increased friction it sees at these points due to the lack of lubrication. Mechanical failure is another issue altogether, its outcome is random and more difficult to diagnose.

Could it have seized or started to pick up at TDC or very close to it then been dragged down the cylinder a short distance before it gave way? Is there any damage or marks to the cylinder wall in the area above the position where the pot came to rest?