Norton noob questions

I've been casually looking for a Commando as a sport touring bike for a bit. My garage is mostly airheads, so I need some Norton knowledge. I'm looking at an unmolested '71 roadster, 13k and in great shape other than a failed layshaft bearing. Still has the original bottom end, but has never been ridden in anger. The price is right-ish, and the transmission work I can handle. My plan would be:
-rebuild transmission w/ new bearings
-check and replace carbs as needed
-replace isolasts
-check swingarm bearings (done 7k ago)
-install EI
-swap on interstate or other larger steel tank
-Go riding. if I still like it after a thousand miles or so, rebuild the motor.

Thoughts on that plan? Other suggestions for reliability?

More general questions:
-How well does the 750 Commando do at speed, as an all-day rider (20% interstate, 70% back roads, 10% gravel)? A little vibration is fine but I want to be able to feel my hands at the end of the day's ride.
-Can I get an old brit twin reliable enough for a week of hard use and curvy roads and camping? I don't expect airhead ride-to-Alaska reliability, but I don't want to live in fear.
-Can I still find luggage for these things, preferably vintage-style? I've got some neat old Wixoms but I don't think they'll fit with the upswept exhaust.

Are you saying it's a 45 year old bike that has only done 13k miles? Hard to believe.

If it has only done that mileage it shouldn't need anything replacing enginewise. Even the weak layshaft bearings lasted longer that 13k miles usually but it is something that you need to be sure is ok. Your plans sound pretty sensible. Carb's will probably just need cleaning. Rubbers in the isolastics maybe tired so sensible to replace and convert to vernier adjustment. The bearings in the swinging arm last a long time, the problem is more often the shaft becoming loose in the cradle. There's plenty of advice on cures in this forum. Electronic ignition is an improvement on the standard set up where the advance/retard mechanism tends to wear and/or fall apart. EI is set it & forget it. If you go for a bigger tank you will have to change the seat too but worth it if you want to go on decent runs.

General answers-

-A Commando will cruise happily at speed. I'm not sure what speed you're thinking of but 80 plus cruising is no problem. There is less vibration than you get on your airhead once you are rolling along.
-Yes you can. In 45 years ownership and riding of my Commando it has failed to get me home twice!
- Not sure where in the world you are but luggage does exist or can be adapted to fit. Craven have started making stuff again in the UK.

Ian

-rebuild transmission w/ new bearings

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Make sure its the roller replacement or the ball bearing with the up-rated cage for the inner layshaft

-check and replace carbs as needed

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The main issue is the slides and body being the same metal, galling eats both up rapidly. So either get them resleeved (different metals) or get new Amal premiers with anodised slides (same cure)

-replace isolasts

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If the current rubbers are ok then got for the Mick Hemmings vernier adjusters.

-check swingarm bearings (done 7k ago)

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The swingarm bearings can wear but the wallowing out of the cradle tube the spindle runs in is more likely, you can get external clamps that fix this.

-install EI

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Go boyer mk4, pazon etc

-swap on interstate or other larger steel tank

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The Interstate is a big long tank, think about rear sets for comfort if you go that way, there is an Indian source for Interstate tanks made from tooling, lots of rubbish ones too so use the forum.

-Go riding. if I still like it after a thousand miles or so, rebuild the motor.

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Sounds good.

Thoughts on that plan? Other suggestions for reliability?

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Fit an oil filter in the return line, AMR timing cover/pump mod to reduce wet sumping.

More general questions:
-How well does the 750 Commando do at speed, as an all-day rider (20% interstate, 70% back roads, 10% gravel)? A little vibration is fine but I want to be able to feel my hands at the end of the day's ride.

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Perfect, no vibration abouve 2500 rpm, thats the isolastics.

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Can I get an old brit twin reliable enough for a week of hard use and curvy roads and camping? I don't expect airhead ride-to-Alaska reliability, but I don't want to live in fear.

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Yes

-Can I still find luggage for these things, preferably vintage-style? I've got some neat old Wixoms but I don't think they'll fit with the upswept exhaust.

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Can't answer that one, never take luggage. Craven luggage is being remade.

13,000 is typically when the carbs wear out and the layshaft bearing gets weak. Resleeve carbs or buy Premiers ? I prefer the Roller bearing as the drive side takes more loads. Luggage for me is soft saddle throwover made by Sidewind. Doesn't touch the mufflers as each bag is slightly tapered . Ride on.

Thanks all, great info. Yes, it's an authentic 13k as far as I can tell - seller has owned since 1983, has detailed maintenance records and has been very up-front. Bike was always stored indoors, he adds zinc to the oil, etc etc. The kind of PO you dream about but never actually meet. The layshaft bearings failed on his last ride, he stopped when it got hard to shift. He pulled the inner cover and has sent pics of the transmission, the inner race is toast but the gears and input shaft appear to be ok. Hopefully we can make a deal and I will be back with pics and more questions.

See if you can assess if there's any damage to the gearbox shell between the layshaft and main shaft bearing supports on the drive side. Likely to be ok but with a failed layshaft bearing I would have a look. Also size up the condition of the layshaft support bushing on the kick start side. Again, worth a look while you are there.

Properly adjusted, The Isolastics should eliminate any vibration felt by the rider at engine speeds above 1200 rpm or so. On the originals (the two prototype bikes) there was none above idle, but the rubbers didn't hold up very well. I've never ridden a production Commando, as none had become available before I left N-V for Boeing. I've never seen one out here in western Washington - British bikes are fairly rare here.

Dances with Shrapnel said:

See if you can assess if there's any damage to the gearbox shell between the layshaft and main shaft bearing supports on the drive side. Likely to be ok but with a failed layshaft bearing I would have a look. Also size up the condition of the layshaft support bushing on the kick start side. Again, worth a look while you are there.

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Any chance you can point me to a pic of that damage to compare? I did a quick Google search, didn't find anything definitive.

Covered in this thread

cracked-gearbox-case-t24119.html

I would recommend to go through the primary drive . it more than likely has a 19 tooth counter shaft sprocket, if so it will be very busy over 60 MPH a change to 21 is IMHO the best compromise. clean and reuse the stock clutch plates along with a dyno dave push rod seal.

bill said:

I would recommend to go through the primary drive . it more than likely has a 19 tooth counter shaft sprocket, if so it will be very busy over 60 MPH a change to 21 is IMHO the best compromise. clean and reuse the stock clutch plates along with a dyno dave push rod seal.

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Thanks for the suggestion. I'll probably ride it before changing the ratios but will keep that in mind if/when I change the sprockets.

Just for kicks, anyone care to put a fair market value range (i.e. swapmeet or craigslist, not ebay or insurance value) on the bike as I've described it, here in the US?

WAG Wild Ass Guess on value as it is described:

$3-4000 as it stands and $2000 needed to make it to a roadworthy $5-6000 Norton.

Fuel tank is probably fiberglass; replace with steel $600
Tires $300
Gearbox repair with new bearings and seals $200
New isolastics (big job!) $200
Carb replacement $300
Carb/control cables $100
Ignition system $300

Excuse my quick stab at the value, I may be well off.
Sounds very interesting, good luck with it.

bill said:

I would recommend to go through the primary drive . it more than likely has a 19 tooth counter shaft sprocket, if so it will be very busy over 60 MPH a change to 21 is IMHO the best compromise. clean and reuse the stock clutch plates along with a dyno dave push rod seal.

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All of what Bill says for sure. I can also vouch for the wisdom of rear set pegs and an Interstate seat as well as lower bars. The combination made a tremendous difference in both the comfort and handling on my 71.

MikeG said:

bill said:

I would recommend to go through the primary drive . it more than likely has a 19 tooth counter shaft sprocket, if so it will be very busy over 60 MPH a change to 21 is IMHO the best compromise. clean and reuse the stock clutch plates along with a dyno dave push rod seal.

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All of what Bill says for sure. I can also vouch for the wisdom of rear set pegs and an Interstate seat as well as lower bars. The combination made a tremendous difference in both the comfort and handling on my 71.

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Good to know. Low bars and new cables were on the wish list, will add seat and rear sets (the list is getting expensive). IMHO, on a naked roadster you're supposed to be leaning on the wind, not leaning back in your easy chair like a lump, or sitting up like a board and fighting it all day. Also it looks cool, and that's the main thing.

Picking up in 2 weeks, can't wait. If anyone has an interstate tank (bonus if signal orange) and shorter seat lying around, holler.

-replace isolasts

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If the current rubbers are ok then got for the Mick Hemmings vernier adjusters.


+1 on that.

I was going to suggest the same thing. If the original ISO's are in good shape keep them. It seems the new rubbers are not made to the same Shore rating as the originals, and increased vibes are felt as a consequence. The Hemmings kits are great apart from the nylon tipped grub screws which get chewed up out after a few adjustments. (I'm going to replace mine with brass ones).

In 1983 I built my 1970 roadster up from a basket case. Not happy with the small petrol tank ( I previously owned a '72 Fastback ), I fitted a Fastback tank which I had left over.
I made my own seat base to suit the tank length and got it upholstered. I also made sheetmetal side covers as the roadster ones didn't fit.

More recently I did a lot of your planned upgrades - EI, layshaft bearings, new vernier iso's.
I found more vibration with the new rubbers but much better handling. The original rubbers were VERY soft. The vibration is not excessive, just more than previous. One or two forum members have suggested drilling the rubbers to alter their effective hardness, not sure of the detail.

I still use the 19 tooth sprocket, but I changed to belt primary drive with a higher ratio.
The advantages of this are:
No oil in primary = no leaks, no checking/topping up
No sticking clutch plates (dynodave clutch rod seal fitted)
Lighter clutch pull by reducing spring pressure ( increased stack height )
No added stress on mainshaft which happens with larger sprocket
LESS stress on mainshaft due to lighter clutch components
Reduced kickstart effort = less strain on gearbox & leg

MFB said:

The original rubbers were VERY soft. The vibration is not excessive, just more than previous. One or two forum members have suggested drilling the rubbers to alter their effective hardness, not sure of the detail.

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Take a look at the last paragraph and to the end of this link: she-back-t16865-45.html#p323887
Mine still vibrates more than original, but I upset the balance by replacing the muffler rubbers, and they're also harder than stock. I have another set on order that's touted as lower durometer, and hope to have an update for you shortly. I do know that the change in these definitely changed the perceived vibration in the bike.

Nathan

The first thing I would look at is the original front brake . It can kill you.

yup to above ..... stopping can become important as your bike begins to run better ....
Craig

Tim:

I just noticed your question about comfort on a long days' ride. Once we got the reliability of the prototypes up to a good level, we started the "endurance" riding, to get as many miles on them as quickly as possible. It settled at a target of 500 miles in a bit over 8 hours and we could design our own routes. My regular route started with about 100 miles on the M6 motorway from Wolverhampton to Levens Bridge then towards Barrow, over the Hard Knott and Rynose passes into Ambleside. I went out from Ambleside to Kendal then to the A66 across east to the A1, A1 south to the A45, west to Coventry and back north to Wolverhampton.

There was no comfort problem for me or the other riders doing the same endurance rides.Vibration was non-existent and the riding position was very comfortable for me (5' 10" in those days). I rode from 04:00 to 12:00 and the other rider did 16:00 to midnight and two other people did the same on a second prototype. The two four hour periods were set aside for maintenance.

Getting paid to ride high performance motorcycles on that schedule was a specially satisfying experience, but it didn't last very long. 20,000 miles per bike took 3 weeks!