Numbers of Conrod Failure over the Years

[Vince]

Let's see how many have first-hand knowledge of this, the blokes who fix them probably know about a few. Engine numbers and models might show some pattern even. And on the other side, it might make some feel safer even.

 

[The Sock]

I've seen only one Triple with a broken rod, on a Goodwood Trackday, ca. '83 (we used to do one a week April through September).
It was a mid '70s, 180°, engine number 3800-3900, IIRC.

 

[pf1]

Ged Shorten at GCS told me that in his experience it's the later engines that let go. Are the rods different?

 

[Vince]

I think Yogis 1200 did this once heading home from a club night, he borrowed my trailer to get it home, if I remember right. I have picked a nerve in my back so wasn't too bright that night.

 

[redax5]

Yogi's Series 2 x 1200 engine

Untitled

Untitled

 

[redax5]

PFC's 80 Jota
Quite lucky on this one, that was the only case damage, easy fix


Case

 

[redax5]

RS's 79 Jota, was repaired by Eades in Sydney back in the day, only lasted for 500 klms before seizing the right side outside main bearing
Crank was assembled way wrong and the alignment of the cases was very bad when welded up
Bike sat for a number of years before it was sent to us to sort out, difficult repair

Untitled

 

[redax5]

and another middle conrod

top case

 

[Paul Marx]

Yikes!

 

[Schurminater]

Look away Perry....Look away!!.

 

[Perry]

This may well prove a worthwhile exercise but at the moment it's not doing me any good at all. I've been having problems sleeping lately as it is !

 

[sfcpiet]

Ged Shorten at GCS told me that in his experience it's the later engines that let go. Are the rods different?

Rods were considerably changed for the 120° engines. Just as afflicted as the 180s.

piet

 

[Thomas aus LAU]

Could you please edit your posts/examples later with:
- Model and year of manufacture of the engine
- approximate mileage of this crashed crankshaft?
- in what situation and at what speed
- original parts or other rods/bearings?

Thanks in advance from Thomas from LAU

 

[pf1]

Well Thomas that might be difficult don't you think? The thing is people who repair things only see the bad stuff because that's what is always in their field of vision. I learned this as a Liaison guy sorting out problems on ships, you only ever see problems, when the actual ship is built and works it comes as a bit of a shock.

 

[redax5]

another one, 81 Jota 7605, damage was everywhere, front, top rear and bottom engine case so have been using this engine for sections to repair other engines

7605 broken case

 

[psg]

.Any pattern as to which rod?
Stu

 

[pf1]

i have just bought a 1200 in bits, about 30 from the end of production. Don't know if I will use the bottom end yet.

 

[1200ts]

It looks like it is usually the center rod that goes bang?

 

[redax5]

It look like it is usually the center rod that goes bang?

no, I would say about even, luck of the draw I would say
have a few more photos of broken rods, just cannot find them, plus a couple of 750 holes as well

 

[sfcpiet]

I've heard of a lot, but only seen a few in real life. About 3 or 4 triples, 3 twins, including my own. Can't recognise a pattern, seems it's a quite random occurrance.

Don't think Lavs are any worse than others of the era, the long-defunct local Ducati-Laverda-MV Agusta guru had a nice line-up of Gallarate MV four cases (nice, long crank, also prone to destructive harmonics) under the workbench, all with supra-ventilation. Seems also the Castiglioni-era MVs carried on the tradition for a while.

Biggest problem is we're still riding/thrashing the bloody things, while the others just stand in their showcases looking pretty.

piet