My new Commando 850 had a dark secret

Dedubyah

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After almost 50 years since owning an 850, back when I was a but a teen, I am once again a Norton owner. I had been following the prices of 850s for a long time and with the current financial squeeze causing a drop in prices, managed to acquire this one.
My new Commando 850 had a dark secret

I bought it through an auction, sight unseen however it looked to be in very nice original condition, which as it turned out, was. The seller told me that it belonged to his son who h.ad it as display piece in his house and it was only occasionally fired up. He gave it a service prior to selling however when he drained the sump, as it was prone to wet sumping as they do, less oil appeared than expected given how low the dipstick read. He drained the primary and a load came out. He let me know that the main seal had failed and offered to either send it to a shop and have it replaced or if I wanted to do the job, give me a generous discount. I told him that I would do it and the bike was delivered to me.
While waiting for the tools to arrive, I decided that I would fire the old girl up and after half a dozen or so kicks it roared into life and settled into a nice idle. I ran it for a couple of minutes then removed the primary oil level plug and about a litre of oil came out. No big deal, a few days later the tools arrived and I proceeded to remove the rotor and drive sprocket when I discovered this
My new Commando 850 had a dark secret

As can be imagined, gut wrenchingly disappointed. The main seal had a lot of red RTV around it and the inside face of the rotor was a bit beaten up as well, so I immediately called the seller and he seemed to be as surprised as me and to his credit he has undertaken to reimburse me for the cost of all the parts needed to repair her, so thanks again Dave. At least I have a half century's more mechanical experience since my first 850 and look forward to getting her back on the road, better than ever.
The bike shows 26,000 miles and to the best of my measuring ability and rechecking each measurement at least a dozen times, has negligible wear in the bores or the pistons at 76.89mm. Just waiting on my pinion puller to show up before splitting the cases. I do have a question regarding my timing cover, I had planned on doing the AMR mod to stop it wet sumping in the future and I see the screw inserted roughly where I see the hole drilled when doing the mod, so can anyone tell me why it might be there? Thanks
Dale
My new Commando 850 had a dark secret
My new Commando 850 had a dark secret
 
You might need a set of crank cases or a talented welder to stop the oil from getting into the primary. Looks cracked here and there around the crank seal.

Hard to say what caused the issue, but it looks like somebody got carried away with a Dremel trying to fix something and never completed the job because of too much damage.

AMR will fix the timing cover if it need fixing. At least I think they will.
 
That screw is factory, a holdover from previous design. Normal.
The AMR screw goes in the engine case, not the cover.
 
That excavation around the boss is a weld prep made with a carbide ball end burr in a die grinder.
It appears the weld repair was not performed, with several possibilities as to why not.
Likely, the weldor wanted it disassembled to clean oil from the backside.
Also, viewing the porosity at about the 9:00 position, it's possible someone TRIED welding, not knowing oil would wick through the crack, contaminate the weld zone and make a horrid mess.

IMG_5622.jpeg

Also, the hammer marks on the end of the crankshaft speak savage mechanic (or owner playing mechanic) in it's past.👹🔨
 
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That excavation around the boss is a weld prep made with a carbide ball end burr in a die grinder.
It appears the weld repair was not performed, with several possibilities as to why not.
Likely, the weldor wanted it disassembled to clean oil from the backside.

View attachment 121627
Also, the hammer marks on the end of the crankshaft speak savage mechanic (or owner playing mechanic) in it's past.👹🔨
The end of that crankshaft is scary to look at!
Mike
 
I believe the grub screw blanks off the end of the drilling between the timing cover gallery and the OPRV and not "a holdover from a previous design".
I was referring to the screw in the photo provided by OP. Which as far as I know can be found in most timing covers. I believe he mistook that screw for the one you referenced which is used in the AMR mod.
 
I was referring to the screw in the photo provided by OP. Which as far as I know can be found in most timing covers.

The same grub screw I was referring to (where's another?) which blanks off the oilway drilling which is the grub screw in the AN link.
My new Commando 850 had a dark secret
 
The same grub screw I was referring to (where's another?) which blanks off the oilway drilling which is the grub screw in the AN link.
My new Commando 850 had a dark secret
1000001535.jpg

This set screw has nothing to do with the AMR mod, the AMR screw is in the crank side. OP posted the photo above in reference to the AMR mod.
 
This set screw has nothing to do with the AMR mod, the AMR screw is in the crank side.

Yes I know and I never said it was part of the AMR mod but a blanking plug not "a holdover from a previous design" as you said.

"OILWAY BLANKING PLUG"
 
Yes I know and I never said it was part of the AMR mod but a blanking plug not "a holdover from a previous design" as you said.

"OILWAY BLANKING PLUG"
Understood.
Genuine question, why was a hole drilled and then plugged?
 
Looks to me like somebody beat the bearing in to the crankcase cold, fracturing the crankcase.
The repair requires welding. Welding will probably deform the bearing recess/crankcase, and who knows what else.
After welding, machining and/or sleeving the bearing recess will be required.
Replacement of the cases would probably be a better solution. Unless keeping the numbers matching is essential.
Comments welcome.
 
Looks to me like somebody beat the bearing in to the crankcase cold, fracturing the crankcase.
The repair requires welding. Welding will probably deform the bearing recess/crankcase, and who knows what else.
After welding, machining and/or sleeving the bearing recess will be required.
Replacement of the cases would probably be a better solution. Unless keeping the numbers matching is essential.
Comments welcome.
I agree that replacing the cases is best. When I've done that, I keep the old cases and if/when I sell the bike, I give them to the new owner so it's clear what was done.

Matching numbers is always best, but unless he can find a machine/welding shop equipped to fix that properly (doubtful) it will just be a mess. I would trust Jim Comstock, if he says it can be done, but I know of no one else.
 
That crankcase is scrap. You can have it welded by the best welder in the world & it will still break eventually. Ask me how I know. Even if you did choose to repair the crack, unless you can do the work yourself, welding & resizing the main bearing bore would cost too much. As for matching numbers, if you buy a new pair of cases you can stamp the number on those.
 
I pretty much figured that the cases were toast. The cost of having them welded, set up to have the bearing housing machined and line bored and the external housing machined, I don't know if I could find a shop here in NZ to do that and be willing to guarantee the job. Fortunately the seller is willing to carry the cost of a set of cases as well as the rest of the parts necessary.
Thanks for the info on the oil relief hole, had been scratching my head on that.
 
Dark secret indeed. Really unfortunate on such a nice looking machine.
Best wishes going forward and keep us up to date.
 
I pretty much figured that the cases were toast. The cost of having them welded, set up to have the bearing housing machined and line bored and the external housing machined, I don't know if I could find a shop here in NZ to do that and be willing to guarantee the job. Fortunately the seller is willing to carry the cost of a set of cases as well as the rest of the parts necessary.
Thanks for the info on the oil relief hole, had been scratching my head on that.
Myself I think the man that will make good on your purchase should be complimented.Nice to hear a good story other than the repairs that have to be corrected.I hope you get a nice motorcycle when all this is completed.
Mike
 
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