1973 850 Rebuild

Mofosheee

Mofosheee

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Hello Forum
I have an 1973 850 (basket case) Engine disassembled;
Cases have been split and parts cleaned with solvent. Engine had been torn down before. Visually, everything looks good;
bore, cam & lifters, bearings, cases, crank , case threads, etc. Pistons = +0.040" . Cylinder head exhaust threads destroyed (out for repair)

So where to go from here? What will I regret not doing at this point? What not to use or do?
For instance, is there a particular main bearing set to install, crank case ventilation mod, oil sump mod, should I or shouldn't I use stainless cylinder bolt hardware,
preferred gasket set and sealant (I hates leakers)

I know there is a link here regarding my inquiry, but I can't find it. Thanks all
 
Mofosheee said:
. Cylinder head exhaust threads destroyed (out for repair)
Click to expand...
Jim Comstock does a AL/Bronze thread repair service (He can also insert the three 3/8's threads at the head gasket joint)
He also does case reed valve systems.


The main replacement bearings are from Andover Norton as are gasket sets etc.
It is a 'case of what is available and in some cases like main bearings (unless you found NOS) that offering is limited.

Wellseal compound is as good as anything for the case joint as long as there are no risers, the stud and other holes have the edges countersunk (imho) , prepped with the likes of acetone and the Wellseal is left long enough to be tacky before assembly.
I wipe/wet gaskets down with the likes of Loctite 515/518 over putting it on the alloy based on you are addressing the contact of the gasket itself.
You have the option of checking and changing the crankshaft end float.
If you went with the sump type reed valve there would be extra work needed at the T/S crankcase wall as far as plugs and sealing.
There is also the option of crankshaft balancing.

Everyone has a way of doing things so there is no one way and maybe more then a few right ways.
I like the thought of spending the time on assembly as in the end you want to just ride/enjoy the bike and do realistic maintenance upkeep.


andover-norton.co.uk

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.
andover-norton.co.uk

There are stockists like Old Britts in the USA.


Edit.
I missed the out for repair already.
 
Last edited:
Time Warp said:
Jim Comstock does a AL/Bronze thread repair service (He can also insert the three 3/8's threads at the head gasket joint)
He also does case reed valve systems.


The main replacement bearings are from Andover Norton as are gasket sets etc.
It is a 'case of what is available and in some cases like main bearings (unless you found NOS) that offering is limited.

Wellseal compound is as good as anything for the case joint as long as there are no risers, the stud and other holes have the edges countersunk (imho) , prepped with the likes of acetone and the Wellseal is left long enough to be tacky before assembly.
I wipe/wet gaskets down with the likes of Loctite 515/518 over putting it on the alloy based on you are addressing the contact of the gasket itself.
You have the option of checking and changing the crankshaft end float.
If you went with the sump type reed valve there would be extra work needed at the T/S crankcase wall as far as plugs and sealing.
There is also the option of crankshaft balancing.

Everyone has a way of doing things so there is no one way and maybe more then a few right ways.
I like the thought of spending the time on assembly as in the end you want to just ride/enjoy the bike and do realistic maintenance upkeep.


andover-norton.co.uk

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.
andover-norton.co.uk

There are stockists like Old Britts in the USA.


Edit.
I missed the out for repair already.
Click to expand...
Thank you for that. The head is already at his shop. I'm fortunate in that James lives down the road from me.
 
Jim did the three 3/8" threads also on the head I sent him as they are known to fail. (along with the exhaust threads and new KW guides)

Why are there no more replies to this thread ?
 
Time Warp said:
Exactly.
Click to expand...
Cuttin no corners. The bike came to me looking like sheet. Surprised how well it's cleaning up. From what I'm seeing (by registration) the bike was taken down and abandoned in 1980 due to cylinder head issues. Revisiting my misspent youth here. Anyway, yes on balance engine, belt primary drive up grade, electronic ignition up grade, looking hard at single carb install, wondering if there is a recommended main bearing version.
 
Item 6 is pretty much the standard go to main bearing replacement these days.

andover-norton.co.uk

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk

Your bike will most likely have an RH4 cylinder head so a good move sending it to the Jedi Master.
 
Correctomundo..... It's an RH4.
Yeah.... Met the highly talented Mr Comstock at his shop a few months ago. Don't know him well, rather interesting person.
Thanks for the bearing recommendation! Was wondering.
 
I would have Jim hardness test your lifters, as he discovered some could be soft. And if one or more is, your cam will wear quickly.
 
Time Warp said:
Item 6 is pretty much the standard go to main bearing replacement these days.

andover-norton.co.uk

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk

Your bike will most likely have an RH4 cylinder head so a good move sending it to the Jedi Master.
Click to expand...
Ordered!
 
Disassemble crankshaft if you have not already done so to clean sludge trap - reassemble with new bolts or studs - whichever yours has - nuts, tabs . Be sure to mark crank / flywheel on one side so it goes back together the same way . Mick Hemings’ DVD on Norton twin engine rebuilds is very helpful - available from U.K. based Norton Owners Club .
As it is .040 over you may want to check crank balance as obviously the pistons are not original.
 
What's the preferred cylinder head gasket please.................
composite
or
copper

Thank you
 
Time Warp said:
Item 6 is pretty much the standard go to main bearing replacement these days.

andover-norton.co.uk

Andover Norton Parts Drawings - Genuine Andover Norton Factory Parts - Commando Parts

Andover Norton Parts are the only Norton spare parts in the market manufactured to original drawings, within the factory-approved tolerances, from the correct materials, and with the correct finish.
andover-norton.co.uk

Your bike will most likely have an RH4 cylinder head so a good move sending it to the Jedi Master.
Click to expand...
 
Mofosheee said:
What's the preferred cylinder head gasket please.................
composite
or
copper

Thank you
Click to expand...
Might as well enquire what is the preferred engine oil.
Some like composite, some like copper.
I've had good luck with copper. Anneal with a propane torch until it turns red. Let it cool and clean up with scotch-brite. A very light coat of K&W CopperCoat spray when you are ready to install.
I've never used the composite on a Commando, but lots of people do.
 
Agree.... I'm seeing that the head gasket controversy has been beat to death here. Each type has it's merits. (I prefer copper) It's WAY easy for me to get wrapped around the axel on details of what I should or should or should not do. To end this debate (for me) is when it fails fix it and press on. No big deal. What I want to avoid is going deep into surgery on the engine,
like splitting cases.

What I found interesting are the guys who replaced the head gasket with the 0.005" copper wire and sealant.
I'm also reading about the crank case case reed mod.... Hum

You opened up another can of worms! Oil. Been thinking about it, haven't crossed that bridge yet. Wondering what are peoples thoughts on the synthetics
Any more rabbit holes? :)
Thank you
 
Mofosheee said:
Agree.... I'm seeing that the head gasket controversy has been beat to death here. Each type has it's merits. (I prefer copper) It's WAY easy for me to get wrapped around the axel on details of what I should or should or should not do. To end this debate (for me) is when it fails fix it and press on. No big deal. What I want to avoid is going deep into surgery on the engine,
like splitting cases.

What I found interesting are the guys who replaced the head gasket with the 0.005" copper wire and sealant.
I'm also reading about the crank case case reed mod.... Hum

You opened up another can of worms! Oil. Been thinking about it, haven't crossed that bridge yet. Wondering what are peoples thoughts on the synthetics
Any more rabbit holes? :)
Thank you
Click to expand...
Plenty of good oil info here:

Follower scar oil tests (2018)

So after having a cam failure and getting sucked into reading way to much crap about oils, I decided if I wanted to know I better do some more testing. I had a Timkin scar tester some years ago but never thought it gave me any good valuable info so I put something together to do some testing...
www.accessnorton.com www.accessnorton.com

Cheers,

cliffa.
 
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