First Norton

I recently purchased my first Norton, a 74 850 roadster. The bike looks perfect in every way, and everything works as it should. The problem is once the engine is good and warmed up after 2 or 3 miles of riding, the right side begins to smoke and a nasty miss to the point of engine stuttering happens. I suspect there is a problem with the head. The amount of blue smoke is considerable, but only happens once the engine is warm. Any suggestions?

Start with the easiest first.
Check there are no air leaks between the carb. & head, & all is tight.
Check balance tube is on alright between the manifolds.
If that lot is alright, check there is nothing come loose in the carb. & choke slide is up.
Tappets not too tight or stupidly loose?
Ign. timing alright?
If it is in the head, it could be a loose guide, or guide seal missing or damaged, or head gasket gone.
Worth a compression check, if you can.

Ugh, welcome to the club of never ending questions and corrections and upgrades.

Some heads are porous and others tend to crack so heat expands to let oil seek its source again in the ground. Could be a valve guide only. Owning a Commando is a test of manhood for me, in will power and resources to stick with it till clean joy.

Yet I've seen fields full of fully fettered Commando looking and running great in the end. I've had 2 Commando in that similar state, but didn't last for one reason or another, some my fault but most like your case had nothing to do with me, but I was the one to recover ny expensive time and labor intensive traditional way.

Nothing for it but get manuals and parts books and tools to take er down then ask what to do next if fault is not obvious right off the bat once exposed to light of day and open wallet and down time.

Steven 'hobot' Shiver -
Arkansas Ozarks, biker wonder land with deer tracers that caused one totaled rebuild of a Combat plud my neck spine and major limb joints.

Blue smoke indicates oil burning.
How many miles on current rings?
Common routes of oil into combustion chamber is rings, worn valve guides or valve stem seals.
Since it takes a little while to happen it may be that after a time the oil supplied to the valves builds up high enough in the valve box to be pulled in through intake valve guide.
Take a look with flashlight into cylinders at top dead center to see if that side shows a carbon build up that appears greater and wetter than non smoking side. If very obvious would indicate problem has been building for a while.
If you can talk to PO ask if this problem built up slowly or sudden.
If sudden I'd think valve guide seal.

I really think having the head off and guides checked probably going to be needed.
If they check out then barrel off for new rings.
Before head off a compression check to see if obvious leak down on smoking side. If yes still could be leaking valve but a leaking valve does not usually cause blue smoke.

Bob

I forgot to ask about condition of plugs.
Black oily on missing side certainly indicates oil.
Wet but not oily indicates intermittant spark and instead of blue smoke you may really be seeing a blackish smoke which is indicative of too rich mixture caused by intermittant spark.
If intermittant spark on one side you then try new plugs, swap plug leads to opposite sides, etc to isolate source of intermittance.