should I be worried about "D" rods?

Been following a few of the threads about exploded engines and weak rods and I got to thinking (probably a bad idea!). Should I be worried whether I have the dreaded "D" rods, and if so, what should I do about them? I have a '74 850 Commando with serial 318XXX and about 13K miles on the clock. I had the head and barrels off a few years ago for a valve job and to deal with a few oil leaks but hadn't heard of "D" rods at that time and didn't think to look at them. Does anyone know how many of these rods have broken and under what conditions? In other words, are they expected to break under regular service or under severe stress while racing, popping wheelies etc? Any thoughts and/or advice appreciated.

Andover Norton/Nick Hopkins remembers the "D" rod myth started with a racer in the 1970s who was no good in the workshop. After an engine explosion caused by his bad spannerwork he blamed the "D"-rods. The myth has since been faithfully repeated by some Norton dealers desperate to sell new conrods to their customers. I have yet to see an engine desaster caused by "D"-rods, but then I have only been in the trade for over 30 years, and have only been vintage racing Commandos personally for 15 years, so what do I know. I only use Genuine Factory Parts in my engines though- no suspect con rod bolts and nuts, "billet" conrods (far weaker than forged ones), wrongly dimensioned big end shells, obscure valves, pistons, rings etc. I'd have no qualms to use "D"-rods in an engine. Oops, shouldn't have said that, Andover Norton may sell less conrods now..........
Joe Seifert

The myth has since been faithfully repeated by some Norton dealers desperate to sell new conrods to their customers

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Well, after a newish rod bolt let go in 2002 (before your time JS) I had to replace one rod and yes I bought into the theory so replaced both rods. With recent posts on the club forum it seems we should be more concerned about rogue pattern? bolts and their source though mine did come in official AN packaging. To their testament only one broke, the other got bent very slightly but remained intact despite straightening out the cap at 4000 rpm.

Thanks guys! I will run whatever rods are in there and enjoy the ride!!

Funny I've just been through this quandry with my MK3, spoke to Nick at Andover and several others and took the same line.

I thought D rods were only in Mk3's. My 77 had 1 D rod and a "normal"rod. I didn't take the chance and replaced the 1 D rod. Graeme

Sorry to see that conrod desaster photo. Never had a conrod bolt go, but heard of it and occasionally saw the result. Not only have pattern bolts been in the market for many years- though the latest ones are the worst so far- but a friend told me recently the torque figures in a pirate workshop manual (Haynes? or its German translation Bucheli?) were far higher than in the official factory manual. Must admit I haven't checked yet if that's true. I never use the pirate "one manual fits all years 1902-2002" type manuals anyway. Though I have them somewhere on my bookshelf in a very dusty state.
Then again, not everybody uses a torque wrench, so in those cases it would't have made any difference!
Joe

ZFD said:

but a friend told me recently the torque figures in a pirate workshop manual (Haynes? or its German translation Bucheli?) were far higher than in the official factory manual.

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Hopefully by that, you are not suggesting Haynes manuals are somehow counterfeit?

Haynes quotes a figure of "25 ft.lb." same as the factory manual I believe, which Haynes usually copied their manual specifications and torque figures from-along with all the other inaccuracies given in the so-called genuine "factory" manuals and parts books.

And perhaps, one day, Andover Norton might actually get around to correcting some of those errors?

To me, Haynes manuals are just that.
As for correcting errors Nick Hopkins, MD of Andover Norton and Commando owner, tried to re-write the 750/850 manual 06-5146, because he thought some passages in it were incorrect resp. could be bettered. For that reason we postponed a reprint for over a year. In the end I ordered a new print run of the old version because we had lots of orders but nothing to offer, and it became obvious that Nick, with his normal work load running Andover Norton, would never come round to finishing the revision.

I have worked with the original version since 1977 and if that was good enough for my workshop personell and myself over the years I thought it will do for the average private owner. And it is head and shoulders over most pirate manuals. However, there are exceptions. If you look into our "book list" under http://www.andover-norton.co.uk/Books.htm, you will note I have underlined the Chiltons and Clymer manuals as a "must have", because I think in some respects they are very good, AND they contain some information that the original manuals don't give, like the differences in balance factors etc.

As for other manuals, on the Triumph sector in particular I notice immediately if customers work with a pirate rather than the original Triumph workshop manual, because these customers then try to order or install bits that their Triumph model never had- because the author of the (Haynes/Bucheli) manual obviously knew nothing about the technical changes over the years. Which may be the reason why our original Triumph 650/750 unit twin manuals- of which 4 different ones for the different model variations exists, but Mr.Haynes tries to condense that information into one manual with less pages- are the best-selling titles in our portfolio of genuine Triumph technical manuals.

The same applies to the Commando manual, though in milder form, as the changes were either minimal or, as in the case of the 850Mk3, so obvious even the layman sees where the Haynes manual is "inaccurate".