Heartbreaking pictures

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Larry S

Larry S

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Last ride out I was rolling down the road when all of a sudden there was a thunk and an immediate loss of power. Something was not good. Pulled the clutch in and coasted to the roadside and called my buddy for a trailer ride home. Pulled the plugs for a look see down the cylinders. What I saw made me sick to my stomach. Chunks of metal debris everywhere. WTF! Pulled it all apart and this is what I found. A severely bent intake valve that completely destroyed my head and pistons. Amazingly the bores were unscathed. I've finally sourced everything needed to get back on the road, I'm just waiting to get my head back from the machine shop. It's getting new valves fitted. If I'm lucky I'll be back on the road by next weekend. New head, head gasket, pistons, rings, valves, intake guides and springs. Quite the chunk of change.
 

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I had that happen in a car when i was younger , @100mph Valve head fell off , piston disintegrated ,conrod punched a hole in the block and tried to dismount the alternator :-) ,Wow did it make a noise , my valve guides got worn and not sure if i had enough Valve spring pressure ,better to have at, cam spec , for more control . You were lucky with the bore , Cheers .
 
That’s a bummer Larry. But you’ll fix it.

Your picture shows damage to both combustion chambers, whats the cause of the damage in the side without the broken valve?

And… any idea why the valve failed ?
 
It has a single VM Mikuni...
www.accessnorton.com

1975 Commando 850 restoration

More progress. Degreased, washed, dried with compressed air and primed my frame.
www.accessnorton.com www.accessnorton.com
...so could one (or both!) of the internal manifold cap screws have fallen out? Or the screw sucked into one cylinder and the washer (if it had one) into the other?
 
Or, perhaps some of the debris from the valve breakage was blown back into the manifold as a section of the valve seat appears to be missing and then sucked into the other cylinder? That's assuming that the damage wasn't caused by a broken piston ring?
All speculation at this point, though.
 
L.A.B. said:
It has a single VM Mikuni...
www.accessnorton.com

1975 Commando 850 restoration

More progress. Degreased, washed, dried with compressed air and primed my frame.
www.accessnorton.com www.accessnorton.com
...so could one (or both!) of the internal manifold cap screws have fallen out? Or the screw sucked into one cylinder and the washer (if it had one) into the other?
Click to expand...
Wow. Something must have gotten in there, admittedly I've never had the opportunity to look closely at a norton single manifold, I can see how those two inner nuts could be an issue. Has this been reported before? Damage to both jugs is confounding.
 
Sorry to see! Weird that both were damaged! Don't throw away that head I know it can be repaired!
 
This stinks Larry- sorry to hear of it . As the others have already asked , why the failure ? Keep us updated.
 
That is hard to look at :( and harder on the wallet. I had a similar thing years ago on an HD panhead, an intake valve snapped just below the keepers. Luckily the piston was on the upstroke, it hit the valve, bent it in the guide and it stayed right there. Got away with just replacing the valve cause I was young, dumb, and poor.
 
L.A.B. said:
It has a single VM Mikuni...
www.accessnorton.com

1975 Commando 850 restoration

More progress. Degreased, washed, dried with compressed air and primed my frame.
www.accessnorton.com www.accessnorton.com
...so could one (or both!) of the internal manifold cap screws have fallen out? Or the screw sucked into one cylinder and the washer (if it had one) into the other?
Click to expand...
Found a manifold cap screw (most of it) laying around by the timing side intake valve spring. It appears that the screw backed out and flopped around breaking the valve spring resulting in the valve dropping. Damage to the other cylinder came about because both intake ports are open to each other with a single manifold. The intake stroke on the primary side just sucked in debris from the timing side. When I reassemble I’ll make sure those manifold screws are blue locktited. An expensive lesson learned. Sourced all parts including the head from Morrie’s Place in Ringwood Illinios. Good people to deal with. Thanks for commiserating with me.
 
A manifold screw cannot get into the valve spring area. That chamber is completely separate to the intake ports and combustion chamber. Do you mean it got into the port and caused damage between the valve / guide / seat ?
 
Larry S said:
Found a manifold cap screw (most of it) laying around by the timing side intake valve spring. It appears that the screw backed out and flopped around breaking the valve spring resulting in the valve dropping. Damage to the other cylinder came about because both intake ports are open to each other with a single manifold. The intake stroke on the primary side just sucked in debris from the timing side. When I reassemble I’ll make sure those manifold screws are blue locktited. An expensive lesson learned. Sourced all parts including the head from Morrie’s Place in Ringwood Illinios. Good people to deal with. Thanks for commiserating with me.
Click to expand...
Sorry for your wallet, glad you are a letsgetpartsrightawayandfixthisbastiddsowecankeepridingandhavingfun kinda guy! Was there Loctite on the manifold bolts? (accident reconstruction team)
 
Larry S said:
Found a manifold cap screw (most of it) laying around by the timing side intake valve spring. It appears that the screw backed out and flopped around breaking the valve spring resulting in the valve dropping. Damage to the other cylinder came about because both intake ports are open to each other with a single manifold. The intake stroke on the primary side just sucked in debris from the timing side. When I reassemble I’ll make sure those manifold screws are blue locktited. An expensive lesson learned. Sourced all parts including the head from Morrie’s Place in Ringwood Illinios. Good people to deal with. Thanks for commiserating with me.
Click to expand...
Sorry about your damage
But as Eddie says the inlet manifold screw cannot get into the rocker box
 
That's a tough one to look at Larry.
I had two studs loosen off on my right hand intake to carb (Amals) once when riding up at North Bay, Ontario. I forgot to blue locktite them in.:rolleyes: It started running on one cylinder. With my buddies we pulled into a gas station and proceeded to dismount my camp gear and tank/side cover to get to those two studs and nuts. I lost the O-ring on that side so I used Permatex RTV gasket maker. 1.5 hours later I was back on the road. Not as catastrophic as yours as the bolts and nuts live outside of the intake tunnels.
Hard lesson learned but You will get it fixed. Check the Con Rod on the valve that failed is not bent.
Cheers,
Tom
 
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