Blown Con Rod
- Thread starter ctsbc
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ctsbc said:
Oil starvation probably-which may or may not have been the result of user error?
ctsbc said:
Any Andover Norton parts supplier:
http://www.andover-norton.co.uk/Distributors.htm
http://www.nortonmotors.de/ANIL/Norton% ... 001&Part=1
Okay, I found a link to the Norvil article on "D" rods here:
http://www.norvilmotorcycle.co.uk/techtalk35.htm
http://www.norvilmotorcycle.co.uk/techtalk35.htm
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hobot said:
If a big end begins to seize, the rod can distort to the point where it comes into contact with something solid inside the crankcase, then one of the big end bolts will usually let go because the crank is still turning. Bolt failure is normally a result of rod failure rather than the other way around but people see the broken bolt and immediately blame the bolt.
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Steve ! How dare you suggest that old self tought repairer's would re-use bolts and with no torque wrenck over tighten them?hobot said:
Why i re-buff your remaks and let you know "WE" old engine tampers only used the best cornflake box's ,loads of red hermite and worn adjustable spanners, and got Fred next door [because he once had a M21] to assist.
As lab said, and yourself; some bigend failure starts the self -destruct process. to which the bolts cop for the blaim.
I had a set of shells that where to big, the shell edges had to be filed to prevent buckling up, Traders sourcing after market parts of un-known quaility is becoming common pratice .fork stanchions being just one item.
Who is keeping a eye on product spec, in an ever growing replacement market..thats driven by bottom line proffit, with a possible wrecked bike for the purchacer of such parts?
I replaced a wheel bearing in the wifes Ford Escort a few years ago, I purchased it from a local Auto-factors, It lasted a week.
On inspection it was possible to file the races! on its prompt return to the shop...the guy said " O another, the supplier gets these from india and re-packs them into his own box's, that have the words Birmingham ,Uk stamped on the box! Here endith the lesson :twisted:
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hobot said:
john robert bould said:
From one of ctsbc's previous posts, I gather the particular rod in question failed on an engine at around 20,000 miles, so there's no evidence (so far) to suggest any parts had in fact, been "re-used" or pattern parts used.
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Dare I say it there is a source open to all Norton owners for spares made to the correct spec, and that explicitly INCLUDES fork stanchions and big end bolts, called Andover Norton.
That said, I suspect the offending conrod bolts came from a well-known "Norton specialist" who manages to sell these without ever buying one from Andover Norton. I can not believe he substitutes the genuine forged item by a turned-from-solid bolt made in China, at a fraction of the price, to increase his profits, can you? Or does the same with stanchions made from an inferior steel, again in China, that he also never bought off Andover Norton, even though ours are made from the correct grade seamless steel tubing that we have to buy two tons off every time in order to get it, as opposed to all others in the market?
Coming back to your problem I should inspect the con rod bolts and look if you have been cheated- details on http://www.andover-norton.co.uk/Pirate%20Parts.htm
Joe Seifert
That said, I suspect the offending conrod bolts came from a well-known "Norton specialist" who manages to sell these without ever buying one from Andover Norton. I can not believe he substitutes the genuine forged item by a turned-from-solid bolt made in China, at a fraction of the price, to increase his profits, can you? Or does the same with stanchions made from an inferior steel, again in China, that he also never bought off Andover Norton, even though ours are made from the correct grade seamless steel tubing that we have to buy two tons off every time in order to get it, as opposed to all others in the market?
Coming back to your problem I should inspect the con rod bolts and look if you have been cheated- details on http://www.andover-norton.co.uk/Pirate%20Parts.htm
Joe Seifert
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ZFD said:
I think ctsbc probably lives several thousand miles from that particular "Norton Specialist" so again merely supposition that any pattern parts are involved.
ZFD said:
However, is Andover Norton still content to supply this "Norton Specialist" with genuine Andover Norton parts? And does the name of that Norton Specialist appear in the list of official Andover Norton parts distributors?
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I would have thought re-using high quality OE bolts with new nuts would have been a much better idea than taking a chance on poor quality new parts?
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ctsbc said:
Tom,
Most unfortunate.
Regarding the above reference to http://www.andover-norton.co.uk/Pirate%20Parts.htm, any chance in having a look at the broken bolt to see if it has any of the signature traits of the apprent "pirated parts"
The Andover article was my first thought when I heard about a fellow AHRMA Vintage roadracer, Doug McRae, took a nasty spill on the banks of Daytona International Speedway a few years ago. They attributed it to a broken connecting rod bolt which locked the engine up. There is an onboard video of it on Youtube; I am sure someone can find the link. Pretty scary watching him lay there (from the onboard camera) unconcious just counting away the seconds before they got there and tended to him.
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Inspect the bolt both for its counterfeit clues and like in my Trixie case if there is a discolored fracture line. A good quality bolt seated well with a new nut should be fine for road bike sane use. We had discussion that very few D rod events occur so I still suspect bolt failure and not big end seizure as crank oil fling can keep that part turning till shells beat up first then seize and damage the rest. I still hold out that rods and Z plates are toughest parts of a Commando. Rods are tough enough not to have the inflamous Al fatigue failure we'd expect after 40 yrs service and no use up date in sight. D rods should break at weak point if something else forces them too is all.
Hobot is likely right as damage to the rod was done at the top of the bolt. I did ask in the Spring about the "demon D rod" to determine if I should replace during this rebuild. Conversation suggested that rods could be used and I proceeded with new nuts but reused the bolts. New nuts were from Norton Andover.
Fortunately damage was done 2/3 time starting engine in the shop--could have been under tightened or the bolt was not appropriate for re-use. I will check my second MK 111-not started yet- for torque but will replace both nuts and bolts.
I am still looking for source for D rods or will the forged rods from Norton Andover replace the original rods?
No damage to pistons or barrels given immediate shut down and can be re-used.
Tom
Fortunately damage was done 2/3 time starting engine in the shop--could have been under tightened or the bolt was not appropriate for re-use. I will check my second MK 111-not started yet- for torque but will replace both nuts and bolts.
I am still looking for source for D rods or will the forged rods from Norton Andover replace the original rods?
No damage to pistons or barrels given immediate shut down and can be re-used.
Tom
Did you follow the earlier link to the D rod article
http://www.norvilmotorcycle.co.uk/techtalk35.htm
Some rebuilders won't use D rods. ?
And for those that like utter certainty in their life, note the comment :-
"(probably took less complex tooling I can only presume)"
http://www.norvilmotorcycle.co.uk/techtalk35.htm
Some rebuilders won't use D rods. ?
And for those that like utter certainty in their life, note the comment :-
"(probably took less complex tooling I can only presume)"
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Rohan said:
At face value cstbc stated "snapped at the bolt" but I am not sure if it was the root cause or collateral damage. In the referenced Norvil article the failed connecting rod has a crack coming down from the bottom of the wrist pin hole. Steve Maney cautioned me about using stock rods in the 1,007cc engine if the bike was tuned for 90-95HP; he had found that the connecting rods would split down the middle starting from the wrist pin hole.
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Well that's informative on how an over powered rod splits up, which is not what I've seen in my couple of rod breaks that occurred "after" an oil comma piston let got then a re-used bolt that had corrosion evidence of fracture gradually creeping to point of no return and quit while on about mere coasting power below 55 mph.
I think what helped the piston let go was before I got Trixie someone had put in Al gasket of standard bore but piston was 40 over so it rubbed itself to death.
I think what helped the piston let go was before I got Trixie someone had put in Al gasket of standard bore but piston was 40 over so it rubbed itself to death.
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