Whoops clang !!

[masterbill]

Hello,

Well it been a long time since I posted - nothing personal

Anyway I thought that I would share this with you.

My Son was riding my TRX to work, he had just overtaken a car - nice and steady doing about 60 when there was a horrible noise. He pulled the clutch in as soon as and stopped. Oil all over the rear wheel etc. We got it home had a look and we could see a couple of holes in the crankcase.

So what to do? Well a Import motor came up on Ebay a couple of days later, had a chat with the bloke and I bought it. This was a while ago, I have now put the motor in and it works a treat - big relief because you hope everything will be ok but you don't know.

I've stripped the old motor down and here are some pictures and to be truthfull I don't what went wrong, piston, rings and bore are fine. Crank is good as are the shells.














Damage to the piston was caused by the rod - but no seize marks , rings are good.
No over heating caused by lack of oil - motor had done 21000 miles - didn't use oil although I kept a good check on it.

Anyone got any ideas ?

Cheers Bill

[Con Rod]

was he bouncing off the rev limiter perhaps?

[Excalibre]

Being flogged is my guess too.

[Smithers]

Oh hell, that to happen to a nice engine ..... no sign of seizure, nice journals and shells, ..... can't see much other than big revs doing that .... hmmm?

[masterbill]

Hello,

Well according to my Son he was being sensible just going nice and steady to work.

I will have to have a word

[cobbadiggabuddyblooo]

This is exactly what my mechanic told me about tee Trx std rods.
Strong item but rev it too much to the limiter and it stretches the bottom cap. Once that has happened its only a matter of time if you continue pushing the limit.
I was a little cruel to my other motor and pushed it close to the limiter on the odd occasion and once I pulled the motor apart ( still running luckily) after 70,000km, I could see the start of the wear on the shells, but that was the culprit from that odd couple of big revs.
Finding that limiter constantly though is a recipe for disaster.
The redline warns you of the danger, the limiter is there for those false neutrals and big free revs not under load.
There is plenty of guys out there with oversize bores , heavier pistons, and a lot higher compression adding more stress on the std rods but they don't have issues because they know the boundaries and realise there isn't much use over revving the Trx.
Is it the std ECU on the bike???

[misterdimwiddy]

It is a very linear break through the section of the rod perpendicular to the rod length.

Looks as though the rod broke and the lower part was then split into a 'Y' shape through upward contact with the liner before it mashed the crankcases.

Can you degrease the fracture face on the small end part of the failed rod and then post some clear well lit macro images showing the fracture face detail?

Fatigue failure should be quite characteristic in appearance and quite different to a tensile failure.

If there are no obvious flaws on the rod surface or internal casting defects (voids) which would have acted as crack initiators, I too would suspect over revving as a likely cause.

Surprises me a bit on a stock motor because my own 89rwhp track TRX never did a rod (only crank big ends) despite sustained (and unrecommended) over revving.

I would be interested to see more close up images.

[masterbill]

Hello,

Std ECU.

Ok I will see If I can do some better pictures

I must admit that I didn't think about over revving.

[masterbill]

Hello again,

Right more pictures










Hopefully some will be what you need.

[sanddune51]

Fascinating!

It looks like the crack propagated from at least stress 2 raisers. I wouldn't be too harsh on your son. I reckon that rod failed due to fatigue set up by one or more of the surface stress raisers.
It's lifespan was I feel dictated by a finite number of compression and tensile stress cycles from the outset.

I'm glad you were able to pick up another engine though.


Mark.

[masterbill]

Hello,

I wouldn't be too harsh on your son

No I won't be, I wasn't sure what had caused it, but over revving didn't come to my mind when I first saw the damage.

On Wednesday I'm starting work for this mob

http://www.formhalls.com/

I have machined a lot of parts for them at my old company and have known them for several years, I did an apprenticeship in engine reconditioning - so I'm going back to my beginnings.

It's been a long time since I have seen anything like this - so I'm not sure, I will take it into them and see what they think.

The new motor is good, after it happened I was going to break the bike but this motor come up and I went for it and I'm pleased I did.

The bike is worth more to me than it's actual value if you know what I mean. She was stolen but I got her back.
Her she is before the blow up. She has now got 6 pot calipers on the front and the engine is now black.



Cheers Bill

[dandywarhol]

Stunningly sharp focus on your fingerprints Bill Good to hear its back together again. I've never seen such damage on one of these without crank failure first causing it.

[cobbadiggabuddyblooo]

I'll stand corrected on my last assumption.
Just showed my mechanic the pics and straight away he pointed out the blueing on the surface where the pin goes.
Detonation is the cause and more than likely bad fuel.
Lower octane fuel will detonate at a lower compression and with this downward force its squished all the oil out of the rod where the piston pin rides. This was the first thing he pointed out.
The shock wave sends a vibration down through the rod and BANG with the crank still forcing the rod upwards as the fuel has detonated before reaching TDC.
You'll prob notice a couple of wear marks on the top big end shells too just starting to form as another trait.
As Mark said, don't be too hard on your son, this could happen to anyone and maybe he just wasn't aware of the signs with the motor pinging.

[masterbill]

Morning.

Maybe it's my expert camera work ,but in the daylight there is no blueing on rod

I've never been able to be to hard on my Son who is now approach 40

Still I have learnt something from this - you use the macro setting on the digi camera to get a really good picture of your fingertips

It is a strange one - now do I keep the good bits or try to sell them

[cobbadiggabuddyblooo]

Must be the shadows on the very first photo as that is the only photo I took a snapshot of and showed him.
Good to hear you up n running already . The crank will always get you a good price as they don't come up very often.