'73 vs. '74 850

What are the differences? Baffled ham can on the '74? Anything else? I always hear of the '74 (last of the rhs Commandos) as the "Holy Grail" Is it any better than he '73?

I've only had this '74, but personally feel that a Commando is a Commando is a Commando and shall always be a Commando. All have their virtues as well as shortcomings.
I tossed the old ham can for trying my patience...wish now I'd kept track of the parts.

Danno said:

What are the differences?

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Lots of minor details. If you compare the 850 Mk1 parts book with the Mk2/2A supplement you can identify them.

http://www.tioc.org/partsbooksnorton/pb-nort-850MK2-2A 06-5988.pdf

Most significant difference would seem to be the Mk2 & Mk2A had the RH10 cylinder head.

Danno said:

Baffled ham can on the '74?

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That's in the Mk1/1973 parts book listed as "060902 Front Plate 750 Air Cleaner" but isn't listed in the supplement for Mk2. Mk2 is 063813:
http://www.classicbike.biz/Norton/Parts/1970s/Commando_Parts_73-74.pdf

The Commando was in a constant state of change throughout its production. In 74 there were 2 concurrent builds, the MKII and the MKIIA which were different. The "A" version had restricted exhaust (bean cans) and intake to meet noise control specs. The MKII had a few improvements over the 73 MKI that may or may not be documented. The frame was reinforced at the rear loop, and the swingarm bushes and spindle are unique. It still has the central fixing bolt but also has the felt oil wicks and welch plugs like a MKIII. I'm not sure whatever else is different other than black cylinders.

maylar said:

The frame was reinforced at the rear loop, and the swingarm bushes and spindle are unique. It still has the central fixing bolt but also has the felt oil wicks and welch plugs like a MKIII.

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The timing of the swingarm oil wicks and welch plugs was later than the first 74, looks to be a running change not model year. My 74 is as previous with the long thin bolt and long bushes, it does have the rear hoop reinforcements.

I think the last of the right hand shift, kick starting bikes is romanticized more because it was no longer produced than any significant changes. The RH10 head is desirable according to our flow expert here. If I understand correctly the 932 carbs combined with that head did actually improve the performance of the bike. The carb manifolds are unique to that year I think, or did they carry that porting through into the Mk3?

The Titanic's '73 frame has the rear loop gussets. Build date 3/73. The ham can I have is of unknown origin, but isn't baffled. No welch plugs in the s/a. Looks like the head is the biggest difference. I have the RH4. Curiously, the head on the SS clone (power unit removed from a wrecked MkIII) is also RH4.

I've read reports that the RH4 is prone to leaking oil through pores in the casting. And yes, the RH10 has 30mm intake ports and needs special manifolds to mate with 32mm carbs.
My 8/74 MKII has the welch plug swingarm.

Whatever was on the cart when they were built. I don't care. I'm happy and have been for many years. Great machines from another era which shall never really be modern. Just like the old Rolls...lots of hand fitting in there done by craftsmen.

I checked the parts list at Andover-Norton and it looks like the RH10 porting was not used on the Mk3 as the manifold listed is the standard 32mm manifold. So more accurately the carb manifolds (32 X 30mm) are not unique to that year (74) but to the head (RH10).

Still I think the final year of right side shift became a romantic symbol of the British bikes more than whether they were actually the best year. It's unclear to me whether the RH10 and RH4 head were produced concurrently with some scheme as to how they were assembled or whether there was a straight run for a certain number of bikes that all got RH10 heads.

They probably just lost the number 10 stamp, so started using a 4 !

maylar said:

I've read reports that the RH4 is prone to leaking oil through pores in the casting. And yes, the RH10 has 30mm intake ports and needs special manifolds to mate with 32mm carbs.
My 8/74 MKII has the welch plug swingarm.

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Never heard about porosity, but there is some evidence of cracking at the intake valve guide boss. I put the guides in the SS Clone's head and the Titanic's are original. No cracks.

I've evidence of oil at every joint on the old doll. I take it as proof of NV concerns over corrosion controls assuring a long life of the machine. I am a grateful owner of their extra effort....Going the extra mile for customer satisfaction...No one even suspected their intention at the time.

Seat was "basketweave" on 73, embossed square pattern on 74. Most people seem to prefer the later pattern, me included. All small stuff in my opinion, bit like arguing the toss on a '68, '69 or' '70 bonnie?

I have a ‘74 850 and was thinking of changing the seat from embossed squares to basket weave, but saw the early ‘stripes’ seat at the AN open day. I rather liked the curved flow of the early seat compared to the big straight blob of my current seat. Decisions, decisions

The 1974 MkIIA (also used on MkIII ) had the slightly longer and offset kickstart crank and different pivot kick lever .It did improve the ability to kick start the engine and the kick lever stayed in the folded in position compared with the previous versions that vibrated out to the extended ready for start and hang up your leg calf muscule.On the down side my 1974 850 MkIIa was the worst Commando I have owned( still own) every item that that could fail did :- cam ;gear box ; swing arm bushes, seals and rear cradle bearing area and pivot pin &tunnel ;head crack between valve guides .All happened within 9 months of ownership (purchase new ) and 7000 miles ,fix one thing and ride some more till next disaster then start on next fix.The most reliable parts were the items made by Lucas .The carbs were also on their way out , slides would rattle about and idle up and down .I felt like ' Wiley E. Coyote ' but without the help of the Acme corporation ,I had norton villiers they were the English version ,failure prone and explosive .A friend had a 850 Mk1(original owner) rode the hell out of it and had no issues and did well over 80,000 miles ,just chains and sprockets .My opinion ,the 850 MkI's and the early version 850 MkII's with the long swingarm bushes and the oil nipple are the versions that in the day were the bikes to own .Today most have been played with and the faults rectified and retro- fitted with worthwhile parts.It is only the 850's that have sat in a shed with little miles covered that your "Holy Grail" has any meaning .

Staytite said:

I have a ‘74 850 and was thinking of changing the seat from embossed squares to basket weave, but saw the early ‘stripes’ seat at the AN open day. I rather liked the curved flow of the early seat compared to the big straight blob of my current seat. Decisions, decisions

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I went with the ribbed top seat for my '74 850. I like the look, and this version seems to have more padding than the other models--a BIG plus!

A little over 150 miles in the past two days just ridin' back roads and secondary highways in the Sierra Nevada foothills. The seat is a pleasure.

~998cc

Staytite said:

I have a ‘74 850 and was thinking of changing the seat from embossed squares to basket weave, but saw the early ‘stripes’ seat at the AN open day. I rather liked the curved flow of the early seat compared to the big straight blob of my current seat. Decisions, decisions

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I am thinking that curved flow was the fiberglass base conforming to the fender over time

Sometime in 74 the rear brake plate and chain guard were changed to accomodate the rubber brake pad inspection bungs.

My 73 has silver barrels from original, did any of the 74's have silver barrels ?
Mine doesnt have a RH10 head.
My race bike came as a 73 although does have a RH10 head.
Regards Mike