D rods or not D rods

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Gino Rondelli

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Just stripped the top end off my Mk3 Commando I've owned for a while, a sudden change of engine noise was traced to the stellite foot coming off a follower, no damage to the cam it would appear so that was lucky. Anyway I always wondered about the rods in this thing, so was eager to look after I first identified the follower issue. Not sure if its wishful thinking but the letter before and after the number looks more like an O to me BUT on the rear of the rod there is a definite D.
I think I already know the answer but what do you guys think?
This bike has done just short of 13K miles at the moment, if I have to put new rods in then I will but if I can avoid it I will?
 
Actually kidding myself on, took more photos, def D's, wishful thinking originally I think.............suggestions?
 
Source a good pair of replacements; used rods are fine if they are round on the ends and straight in the middle.

Good thing you found that stellite foot issue before it started swimming around the bottom end with the stump chewing up your cam. (I suppose the extreme valve lash gap would have identified itself pretty quickly)

I had Megacycle refurbish a couple of sets of followers for me, I think they can identify suspect followers. new ones are PRICEY, I managed to find a good used set right here by posting a "Wanted" advert.
 
Gino, Yes you know the answer already!! It's the one thing Les E makes sense on. I used the new Andover rods when they were first reforged in early 2003. Have nearly 26k on them now. Look like they come with a shot peened finish, slightly rough surface.
 
Hehe, I've come to call these suddenly realizations, my Brit Iron Blank Starring State.
Trixie Combat 1st seizure gave me BIBSS, to see slotted pistons and Al gasket ugh.
Anywho, I've a spare rod out of a 750 from a ancient vendor a Barber's swamp meet.
$50 + shipping. Barbers is next wk, might find same vendor and deal again if you like.

hobot
 
I have 1 NM23258 R9R rod left over from my 1973 commando 850 for sale if you need it.
 
Thanks guys, my afternoon has been spent contemplating a further boost to Andover Nortons profits, not sure about the wisdom of using second hand rods, and mismatched ones? I've been bitten before by using Second hand stuff in a rebuild and swore I wouldn't do it again but open to persuasion.
Luckily I have a set of refaced followers in stock so thats one problem taken care of. Motor out tomorrow I think to assess whats needed.
 
Duh, unless you buy super hi end after market rods, there are only used ones around.
BUT so what next to the Z plates Norton rods are the most over built item on Nortons. Rods excepting the D two piece come apart version never cause failure themselves, they only fail after something else goes first. Have no worries about used rods as long as still true and holes correct and not nicked badly.
If you are in a spending mood, get Jim's piston/steel rod set, but its way way over kill for engine not run over redline at full loads for over a minute intervals.
What you should worry about in street bikes run normal to illegal speeds in cast iron flywheel time bomb, not robust Norton Al rods.
 
Gino, don't forget to make sure that your refaced followers are the later lost-wax cast type with the spigotted stellite pads. No point in risking a second one coming off. There was a real plague of detaching follower feet in the early 1980s. There were no official ones available and one dealer told me that LF Harris had been making the patterns which had been failing but of course even the OE ones at that time were not immune from the problem.
 
Now I'm in a quandry, I have seen two grenaded motors in the last year, one a 750 and one an 850Mk3, BOTH caused by big end bolts failing. The Mk3 had D rods and they were not the problem.
Spoke to Andover Norton this morning and was told that they didn't think there were issues with D cast rods under normal (road use) and it may be a rumour put about by unscrupulous parts suppliers
So here I am, overalls on and wondering WTF to do? My worry is that I could spend a small fortune rebulding the bottom end have the thing explode anyway because of new parts failing or I just nail it back together and enjoy?
The bike rarely gets revved over 4500RPM and most of the time operates in the 3-4000 RPM bracket
 
Gino,

I'm with AN on that one. Personally I've never had a "D" rod fail, and I used them in several race motors that were regularly revved to 8000. The only commando rod that I have actually seen fail had been bent previously and then straightened in a vice a couple of seasons previously (not one of mine though!) I think it's a rumour spread by someone who has shelves full of secondhand rods that they want to sell at inflated prices! :)
 
Gino,
Just sold my 850 rods on ebay, I got AUS $200 for them, they were perfect condition, the engine had done 22,000 miles and shells were original and still pretty good. So just missed out on mine. But if anyone else here is doing the Jim Schmidt conversion, you maybe abe to get their old rods. Or if you have a few spare quid and really want a worthwhile upgrade, go the whole hog and order some of Jims light Je pistons with his longer Carrillo rods and special gudgeon pins. It cost me about AUS $1500 and apart form the stuff being pure sex, it will ensure the whole engine will last forever as the destructive vibes are greatly reduced, and rider enjoyment goes north also :D :D :D :D

If you are commited to new Andover rods, this kit might make good economic sense?

Cheers Richard

P.S. Gino maybe u could look at Jims BSA coversion for the cam followers, if the new Norton ones are exxy, this maybe another improvement for similar or less money?

Cheers mate.
 
stockie1 said:
Gino,
Just sold my 850 rods on ebay, I got AUS $200 for them, they were perfect condition, the engine had done 22,000 miles and shells were original and still pretty good. So just missed out on mine. But if anyone else here is doing the Jim Schmidt conversion, you maybe abe to get their old rods. Or if you have a few spare quid and really want a worthwhile upgrade, go the whole hog and order some of Jims light Je pistons with his longer Carrillo rods and special gudgeon pins. It cost me about AUS $1500 and apart form the stuff being pure sex, it will ensure the whole engine will last forever as the destructive vibes are greatly reduced, and rider enjoyment goes north also :D :D :D :D

If you are commited to new Andover rods, this kit might make good economic sense?

Cheers Richard

P.S. Gino maybe u could look at Jims BSA coversion for the cam followers, if the new Norton ones are exxy, this maybe another improvement for similar or less money?

Cheers mate.
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Or you could just leave the rods as they are, fit new big end bolts and have your crank balanced!!! Also, a new set of "standard" Carillos cost £500 if you want to keep it bulletproof!
 
fit new big end bolts
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Now thats a worry in itself, the two grenaded motors I saw were due to bolt failure!
This bike is used for cruising and touring prob about 2 - 3000 miles a year, for serious work I use a pre Mk3 and for being a hooligan my fastback or JPN Rep.
Do I want to spend a fortune, no! Do I want an exploding motor, no
Christ why do these decisions have to be so difficult...... at the moment I'm looking at leaving it as is, not going to rush in, I'll take a week to get opinions................
Thanks guys!
 
Gino Rondelli said:
This bike is used for cruising and touring prob about 2 - 3000 miles a year, for serious work I use a pre Mk3 and for being a hooligan my fastback or JPN Rep.
Do I want to spend a fortune, no! Do I want an exploding motor, no
Christ why do these decisions have to be so difficult...... at the moment I'm looking at leaving it as is, not going to rush in, I'll take a week to get opinions................
Click to expand...


I don't think there's any suggestion that all D rods will fail, only that a certain percentage of D rods were (to quote the Norvil info.): "prone to premature failure" and that "Failure often occurred between 18000 & 22000 miles....but failure can occur at any time.".
 
As a precaution, you could take your current rods to an automotive or aircraft engine reconditioning shop and get this treatment:

1. Magnaflux or dye-pen NDT check for micro cracks. If they exist, ditch the rods. If not do 2 and 3.
2. Resize the bottom ends- this reinstates the big end journal to a perfect circle.
3. Stress relieve the rods with polishing and shot peening.

This should be cheaper than new rods and give you peace of mind for lots of miles.

Mick
 
Good advice, even for cranks. Ed-Geoff Collins of Offset Crank fame got one of his shops to set up to shot peen Al rods for Ms Peel, so now offers that service.
If you know of other Al rod shot peen shops let us know please. Peel changed her mind like a woman or a man, prefering Jim's kit for extreme usage, so Trixie gets
ex-Peels peened Al rods. Installed already.
 
All good advice, but a total waste of time if the rod has an inherint internal forgeing flaw, Emroids probably only had two rods break ,but that would still be enough to put me off.
 
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