28 replies to this topic

[R1minimagic]

To me that looks like sustained high loading on the bearings.

[MRA]

Oil has nothing to do with this failure, its down to the thrusts failing, either due to incorrect fitting, debris, or incorrectly adjusted clutch.
How old is this engine?
Was the crank hardened?

Paul

Hi Paul,

Please can you explain why you are suggesting that it is the thrusts that have caused the engine failure ?

Regards Martin

[samsfern]

the thrust washers would drop/fly out , cause some chaos with the gears, whichl would produce a load of metal particles, cant see it doing that kind of damage though. How many miles has the engine done?

Edited by samsernie, 26 March 2010 - 09:58 PM.

[Paul Wiginton]

Oil has nothing to do with this failure, its down to the thrusts failing, either due to incorrect fitting, debris, or incorrectly adjusted clutch.
How old is this engine?
Was the crank hardened?

Paul

Hi Paul,

Please can you explain why you are suggesting that it is the thrusts that have caused the engine failure ?

Regards Martin

1, Because the OP said the thrusts had failed.
2, Theres bronze deposits on the shells
3, Ive had exactly the same happen

Paul

[bmcecosse]

It's been SHORT OF OIL!! Either because the pump couldn't keep up (was it a 'steel back' pump?) or simply due to surge on corners and possible low oil level. Did it have a centre pick-up pipe ? And when you say it had low pressure 'due to a compressed relief spring' - how low, and what do you mean by compressed spring??? Did it have a ball-bearing relief valve ?? Don't see ANY reason to suspect thrust bearings!

[R1minimagic]

There's not a bronze deposit, it's simply worn through the surface layer of the shell (aluminium, tin or whatever they are) and showing the copper layer underneath.

That can happen for any number of reasons, only the owner knows what sort of duty cycle the engine has undergone so it is anyones guess.

[Paul Wiginton]

Hi Guys,

I recently replaced the primary gear bushes to only find out the thrust washers were stuffed and the crank was floating in the block.

Cheers
Tim

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[bmcecosse]

If there is sufficient oil the crank journal should ride on a cushion of oil and NEVER touch the bearing surface! This damage happens if there is a SHORTAGE of oil! It's not just worn through - the bearing has started to break up.

[R1minimagic]

yes or sustained high loading which will squeeze that micron layer of oil out and metal on metal contact occurs.

[mniguy_nz]

Oil has nothing to do with this failure, its down to the thrusts failing, either due to incorrect fitting, debris, or incorrectly adjusted clutch.
How old is this engine?
Was the crank hardened?

Paul

I adjusted according to Hayne's not to say that I got it right. As for age the thrusts were the second set of oversized fitted and lasted 2000km's, also had a regrind and rebore/pistons and bearings at the same time.

Thanks everyone for the help though. Good to know what to look out for

[MRA]

Here we go, some info that may help,

[attachment=97099:Bearing_...ankshaft.pdf]

[Paul Wiginton]

OP says the 'thrusts wore and the crank was floating in the block'
If the thrusts wore, then are you saying none of that swarf entered the bearings? Impossible, ofcourse it did.
Obviously if I have read the OP wrong and the thrusts have not worn then yes oil is the problem, Im reading what was written.

Paul

[MRA]

I don't think that is what is being said here, however when thrusts fail, you tend to get side wear on the big end bearings due to them twisting on the journals, but there is only minor damage to the bigend bearings, when considered against the mains that is

The last picture on the link I added above is of cavitation on a bearing, this is a very early stage failure, often overlooked because it rapidly leads to other bearing failure

[Paul Wiginton]

My thrusts failed in exactly the same way, my bearings looked just like these, I know what it looks like