Heads came off conrod bolts????

Has anyone seen this happen. Happened to me yesterday.
After being out doing a rece fro our Tutukaka rally in May, I was 40 mins from home when I heard this strange rattling sound. previously I had heard something but it seemed like the Hi Vis Vest I was wearing was flapping in my left ear. when it happened I slowed down and put it in top gear while I listened. Next thing it ran on one cylinder so I shut it down. called the wife and got her and my son to come and pick me up with the Ute and ramps etc. tested the cylinders when I got home an found the L/H ex valve leaking badly..Got the head of this morning and couldn't see much wrong but when I rotated the crank back and forward at TDC, the L/H cyl was lagging behind the action of the other one. Noticed also the marks left by valves hitting the piston. Removed the cylinder and to my surprise, found the heads appeared to have come off the con rod bolts, and the B/E cap was jammed in place and leaving a 6mm or so extra clearance. Looked at the head again and saw the obvious shiny edges where the valve had hit the piston.

As it looks like a lot of money is going to have to be poured into this, I wont be doing much to this till after the rally where I will be riding the semi restored 750.

I have done about 24,000 mile on this bike and apart from seals, m/cyl mod and new pistons, I have never had the crank cases apart. It has always wept a bit of oil from the crank, but since fitting the new pistons and the Jowet breather valve, never leaked anywhere above the crank seal. Oh well, at least I can now seal the crank case properly and fit helicoils to the front 2 head studs.
Incidentally, I had used a very thin smear of Automotive silicone sealer both sides of the copper head gasket when I put the engine back together and the head gasket has never leaked oil, even with the front studs not holding. I only found out about those studs being loose after putting the head back on, and because of the mission to get the head on decided to take my chances,.

I think I have been very lucky so far. Time will tell if I am that lucky.
Dereck

Sorry to read that Dereck.
Have you had a look on the Andover Norton site, on the pirate parts page there is a comparison pic of the Andover bolt and a knock off version.
Would be interesting to see which one yours looks like.
http://www.andover-norton.co.uk/Pirate%20Parts.htm
Will catch up at Tutukaka.
cheers
iain.

Sorry to hear your bad news Derek. I'd suspect either "fake" bolts as Ian mentioned or perhaps the bolts had been re-used on a previous rebuild,
other than that maybe they'd been over tightened.

Pics please

Or- something else happened first, like a "normal" big end failure.

old rod bolts can develop cracks corrosion gradually works across micro grains till about half way then lets go and happened to me and MacRae but ours both sezied so more me$$ than yours> I"d suspect your bottom was older than the counterfit bolt but won"t know till ya exam for this> Look close at any bolt fracture lines> Also its standard praction to trim around rod bolt head seats to avoid shaving a sliver of alu under the head that can lever bolt apart>

I have seen a few rod bolt failures. You are lucky to have stopped your engine in time. Usually the result is a large hole in the crankcase.
I make a habit of magnafluxing the rod bolts when assembling an engine -but they still worry me a bit. Jim

Jim,

Are there any off the shelf ARP quality bolts that are a direct drop in to a Commando rod?

Dances with Shrapnel said:

Jim,

Are there any off the shelf ARP quality bolts that are a direct drop in to a Commando rod?

Click to expand...

Not that I have found. Jim

One of the other things that occasionally causes a rod bolt failure at the heads is incorrect installation of them. The bolt heads are eccentric, and have to be rotated to the right orientation to fit into the counterbore in the rod. I've seen rods where the mechanic (?) didn't realize that, and installed them the wrong way. If you torque them down that way, the head scrapes off aluminum from the rod, and captures it under one edge of the bolt head. That puts a bending stress on the head, and the bit of aluminum under the head also eventually gets squeezed some more, which reduces the clamping force of the bolt. That increases the impact force on the bolt as the piston changes direction at TDC, and eventually the bolt breaks. You can probably see if this has happened to your engine by careful examination of the counterbore in the rod, unless it's been beat up too much to see any detail.

Ken

Do not forget the pirate bolts have been back to back tested with the AN bolts and proven superior by a independent UK tester

So take the AN blog with a big pinch of salt ( it is not in their interest to have competitors producing better components)

Good luck with the re build

Frankie17 said:

Do not forget the pirate bolts have been back to back tested with the AN bolts and proven superior by a independent UK tester

So take the AN blog with a big pinch of salt ( it is not in their interest to have competitors producing better components)

Good luck with the re build

Click to expand...

So where can we find these results as this would be a good one to flush out. Not challenging you here but just wanting to see who (independent UK tester), what (what type of testing - UTS tests, durability tests etc) and how much better.

Hi there. I was tired when making the assumption that the heads had come of the bolts. I felt round with my hand and it was the lack of a nut I thought I felt. I will let you know what it really is when time allows. One of our locals Jim Murdoch used to work for Lotus Racing in the late 60's - 70's and he had never seen such a thing happening before.
While looking I did find a crack in the top rear bolt lug on the r.h case where it is attatched to the g/box cradle. At least I can have the welded up easily now once the cases are split. I am a little annoyed , that after doing the main seal, and correcting my carb problems that I have to do some of the work again. Piss. I was running the new Iridium spark plugs as well [ first time out ] so one of my thoughts was here go'es another $25.00.

I am glad I don't use ear plugs while riding. I like to listen to the sounds my machinery is making. I have seen too many stuff ups as a result of ignorance. Like the 2.5 litre Daimler that drove 70 miles with no piston on its gudgeon. { it hardly made a noise, but I heard it }. What a lovely mess of its bore it made.
Triton Thrasher, I know what bearing noises are so can assure you, there were no bearing noises previous to this, so there may be no damage to the shaft. I must admit though that even recognising bearing noises, the noise this time had me wondering.
Dereck

PS my wife rubbed it in that I should have bought a late model bike instead of this second bloody commando. Bless her.

Norton Commando Big End Bolt 06-6486
In August 2012, an independent Quality Assurance Testing House issued a Test Certificate in relation to 4 separate Norton Commando Big End Bolts.
The bolts were tested for Tensile strength, Hardness and Failure location.

The 4 bolts tested were as follows :-

1-i) Wassell forged bolt WW26244 as supplied to Norvill Motorcycle Company and dealers worldwide
1-ii) An Original Norvill forged bolt
2-i) and 2-ii) Two stock bolts supplied by Andover Norton.

The results of these tests can be found below. These Quality tests were not commissioned by Wassell Ltd, and therefore we have respected the confidentiality of the proprietor.

Test Certificate August 2012

Wassell Limited would like to reassure all our dealers, and the public, that the Norton Commando Big End Bolt that we supply is both forged, and uses rolled threads.

Hi Frankie17.
The test certificate link does not work.
Please provide test data / results of testing.
Ta.

The Bolts were submitted for test by an independent UK dealer and copies of the test results were circulated ( by the manufacturer of the bolts )

the actual link comes from Wassell and they also have a copy test certificate supplied by UK dealer ( Wassell are a distributor of these Uk made bolts )

Not the manufacturer

From memory the big end bolts and associated nuts are the most highly specified parts on a Commando. In terms of material, tolerances, surface finish, processes mandated (thread forming etc), nothing else comes close.
cheers
wakeup

kerinorton said:

Hi there. I was tired when making the assumption that the heads had come of the bolts. I felt round with my hand and it was the lack of a nut I thought I felt. I will let you know what it really is when time allows. One of our locals Jim Murdoch used to work for Lotus Racing in the late 60's - 70's and he had never seen such a thing happening before.
While looking I did find a crack in the top rear bolt lug on the r.h case where it is attatched to the g/box cradle. At least I can have the welded up easily now once the cases are split. I am a little annoyed , that after doing the main seal, and correcting my carb problems that I have to do some of the work again. Piss. I was running the new Iridium spark plugs as well [ first time out ] so one of my thoughts was here go'es another $25.00.

I am glad I don't use ear plugs while riding. I like to listen to the sounds my machinery is making. I have seen too many stuff ups as a result of ignorance. Like the 2.5 litre Daimler that drove 70 miles with no piston on its gudgeon. { it hardly made a noise, but I heard it }. What a lovely mess of its bore it made.
Triton Thrasher, I know what bearing noises are so can assure you, there were no bearing noises previous to this, so there may be no damage to the shaft. I must admit though that even recognising bearing noises, the noise this time had me wondering.
Dereck

PS my wife rubbed it in that I should have bought a late model bike instead of this second bloody commando. Bless her.

Click to expand...

I wish I had that sort of luck, I'd buy more lottery tickets. Don't buy yourself any Ducatis. My friend used to work on them. No job ever brought a bill that was less then $5000, and most of the bill was usually due to guys trying to fix them, themselves. There is nothing brilliant about a commando, however you still have to 'do it right first time'.

kerinorton said:

Hi there. I was tired when making the assumption that the heads had come of the bolts. I felt round with my hand and it was the lack of a nut I thought I felt. I will let you know what it really is when time allows. One of our locals Jim Murdoch used to work for Lotus Racing in the late 60's - 70's and he had never seen such a thing happening before.
While looking I did find a crack in the top rear bolt lug on the r.h case where it is attatched to the g/box cradle. At least I can have the welded up easily now once the cases are split. I am a little annoyed , that after doing the main seal, and correcting my carb problems that I have to do some of the work again. Piss. I was running the new Iridium spark plugs as well [ first time out ] so one of my thoughts was here go'es another $25.00.

I am glad I don't use ear plugs while riding. I like to listen to the sounds my machinery is making. I have seen too many stuff ups as a result of ignorance. Like the 2.5 litre Daimler that drove 70 miles with no piston on its gudgeon. { it hardly made a noise, but I heard it }. What a lovely mess of its bore it made.
Triton Thrasher, I know what bearing noises are so can assure you, there were no bearing noises previous to this, so there may be no damage to the shaft. I must admit though that even recognising bearing noises, the noise this time had me wondering.
Dereck

PS my wife rubbed it in that I should have bought a late model bike instead of this second bloody commando. Bless her.

Click to expand...

The same thing happened to my '75 in 2007 not long after I bought it. I was tinkering around in the garage with it, I started it up and started hearing the knocking sound. Lucky for me it happened right there in there garage before it could do catastrophic damage. I have a pic somewhere I think.