things that rattle and bang, aka bottom end failure! (2010)

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Wilco

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Aug 3, 2009
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A few days ago, I washed and oil changed the commando. The sun was out, so I headed into town to fill up with petrol..
But only a few k's down the road, the quiet clatter of the engine became a loud clatter, and then a rattle.. It started to run out of power, and before I could wonder what the F was going on, CLANG CLANG CLANG CLANG! the bottom end (I think) threw a hissy fit.
I am in the process of removing the engine and splitting it apart to investigate and rebuild (apart from not having a 1/4"WW socket for the head bolts!) and I have never done this before so I seek advice from you, the wise council of norton elders..

Q1. Crank grind & balance : should I seek out a brit cycle specialist or would any competent motor machinist handle this?

Q2. Replacement parts : aside from bearings, oil seals, gaskets etc, what parts would be sensible to replace/recondition while the motor is apart?

I am off now to seek out missing socket, then home to continue engine removal, will provide pics of damaged components soon..
 
Well, I'd have a hard look, with Superman-type x-ray vision, at those rods for one thing...
 
Wilco, does the guy Hobson still have a machine shop in Feilding, any '' competent motor machinst'' could handle this , but they dont seem to want to.
Finding someone intrested that won't do any more damage is getting harder these days
 
Wilco, Bummer that is pretty unsual!

So I would have to ask, sorry. But could the oil change proceedure have had anything to do with the failure? Well worth double checking stuff.
As for the crank, the most important thing for a crank grinder to know is the radius, thus needs to be right, too bigger radius and it will catch on the shells, too small and you risk cracking the crank. Mains should be converted to super blends, plenty of literature on tracking down the right bearings, The place in ENZED at Wellington should have these, and most other parts. Assuming the rods are still okay, new nuts is a must. Aslo clean out the sludge trap in the crank.
Check the oil pump, as you dissasemble to ensure ity is driving, and pay attention to the seal in the end of the timing case, the one the nose of the cran goes into. If this is not right all oil pressure is lost.
If the engine is a 750 u can take the whole barrell off with the head attached?

Hope this is a start and let us know what you find?

Cheers Richard
 
I have the engine out of the frame now, and the head is off. Will be splitting the cases tonight..

Initially I thought I had forgotten to tighten the sump plug and it had fallen out, but it was still there. I couldnt find anything else externally that was not right after the oil change.

Also, the wet sumping of the engine has been getting progressively worse this year, to the point where there is so much oil I couldnt even kick it over. My procedure had become one of draining the oil into a clean container and tipping it back in the oil tank. The last time I did this, I saw lots of metal shavings in the bottom of the container. Perhaps this, combined with the wear in the pump indicates some excesssive wear and tear going on inside the motor?
 
Take apart crank to clean sludge trap and inspect the crank journals. If not seized then likely just normal wear stuff to replace, rod shells crank bearings. Maybe pistons beat up. Might have valves checked re seated. Also make sure swarf is cleaned out oil pump and oil passages. There are a number of Norton crank balancers to choise from and worth while to get dynamic balanced for the long term.
Use new rod and crank bolts, or may get one of my hard lesions thinking mild operation is any safe guard on them. Read up on rod bolt seating issues to be aware of and use rod bolt stretch of .0065-.007" to set them, not torque wrench.
Inspect oil pump case close for cracks. I like Racer Blue Hylomar for all sealing needs, though a thread laid in case and barrel bottom seams not a bad idea.
Rods and crank should be magnafluxed and checked for trueness.

Get the bent/crooked 1/4W box end wrench for easier rear head bolt access and most other fasteners. I use razor blades to get the cases started to part from glued sealing.
 
If you don't use a knowledgeable Norton machinist and the crank needs to have the journals ground undersize, make certain they can properly grind the radius in the journal. If you have any doubt, find a different shop.
 
I got a used TS crank cheek, re-ground .01" under from Baxter's for ~$175 for idea of cost to compare. If I'd shopped might have gotten cheaper but for time and quality questions comfort I paid Baxter's premiums. Barrel could be scored too, ugh.
 
things that rattle and bang, aka bottom end failure! (2010)

things that rattle and bang, aka bottom end failure! (2010)

things that rattle and bang, aka bottom end failure! (2010)


The big shells are egg shaped, the rod has gouged on the cases and bent, and the piston has hit the flywheel. this is on the timing side, the primary side is completely untouched and does not even show signs of excessive wear.
The barrels are not scored or worn.
The cam lobes on the primary side are worn excessively but I think they have nothing to do with the above damage. It does explain though the top end clatter that it always had.
Diagnosis anyone?

Q1. I assume I should replace both rods and both pistons and not just the damaged ones?

Q2. There is visually no damage to the cases but will they be ok?
 
If this was an oil pressure problem I would have expected the primary side to go first as this is furthest away from the pump, so a bit lost as to why the timing side failed first. How tight were the con rod nuts on the failed rod, maybe one loosened off and the bearing failed due to excessive clearance reducing oil pressure.

I would change the failed rod making sure it weighed the same as the good one and fit new pistons but if the reason for failure can be found out this may change. Cases should be fine but will need a good clearout to get rid of the debris.
 
They're 'D' rods, so I doubt they are the originals!


kommando said:
How tight were the con rod nuts on the failed rod, maybe one loosened off and the bearing failed due to excessive clearance reducing oil pressure.
Click to expand...

I know the late John Hudson always maintained that the hammering from a failed big end would cause the nuts to loosen-rather than the nuts loosening off being the actual cause of the failure.
 
John also used to make a point of refering to the sliver of ali that could become trapped under the head new con-rod bolts if the sharp edge wasn't eased prior to assembly and that this could lead to incorrect torque and subsequent problems.

All in all, I think that you've got off lightly here. There is a lot to replace but you've still got your cases and your frame's not bent !
 
What surprises me, is even though the rod has obviously bent fore-and-aft, it seems strange that the piston could have been pulled down far enough into the flywheel for it to have removed that amount of metal from the bottom of the piston, it's as if the rod had shrunk?
 
79x100 said:
John also used to make a point of refering to the sliver of ali that could become trapped under the head new con-rod bolts if the sharp edge wasn't eased prior to assembly and that this could lead to incorrect torque and subsequent problems.
Click to expand...

7900,
I want to make sure i understand this little jewel of information. I am confused by the term "head'. Is the sliver developing between the head of the crank bolts and the lower bearing shell, or somewhere else on the head bolts.? I would think your referring to the rod bolt head but I just want to make sure. Now I hope I have use the right term for the bearing shell?

gary
 
T95 said:
I want to make sure i understand this little jewel of information. I am confused by the term "head'. Is the sliver developing between the head of the crank bolts and the lower bearing shell, or somewhere else on the head bolts.? I would think your referring to the rod bolt head but I just want to make sure.
Click to expand...


Nothing to do with the bearing shell or conrod cap. If the head of the conrod bolt has a sharp edge, it can shave off a small amount of alloy from the conrod as it is drawn into its recess as the bolt is tightened, and that shaving of alloy then lodges under the bolt head which can cause what 79x100 has described.

things that rattle and bang, aka bottom end failure! (2010)

(Triumph conrod bolt shown above)
 
L.A.B. said:
Nothing to do with the bearing shell or conrod cap. If the head of the conrod bolt has a sharp edge, it can shave off a small amount of alloy from the conrod as it is drawn into its recess as the bolt is tightened, and that shaving of alloy then lodges under the bolt head which can cause what 79x100 has described.
Click to expand...

L.A.B.,
I would of suspected the nut, as it was tighten, to create the problem rather than the head of the bolt. Thanks for clarifying that for me! Now I hope I can retain it until I bust into my project.
G
 
L.A.B. - "D" rods? What kind of rods should I be using to replace? And what kind of pistons?

considering that the motor was fine before this, are there any of these non-damaged and little-worn parts I could not replace? Should I keep the crank bearings? Or should I just replace everything?
 
Wilco, Im afraid most all of the internal in your engine are toast,pistons ,one rod at least , camshaft, lifters, all beaings( cam bushes may be okay), oil pump depending on how much crap has gone through it, the crank 1/2 could also be damaged beyond repair$$$$$$$$$$$$$$$$$$$.
 
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