1974 Norton Commando

Why a Norton?

There was a local British motorcycle shop that I purchased parts from when I restored my Firebird Scrambler. They held British bike rides, which I attended with my BSA. It did not take me long to realize that Norton Commandos outperformed the BSA in most areas. After riding the BSA for several years I started to look for a Norton. I found two of them in a local paper that were being sold in a town not too far away. When I went to look at them, the same day they were advertised, one was already sold. There was a Pacific Coast Blue 74 left. The other bike was a 71 Combat, much better looking in my opinion, but as I later learned the 74 was a better running bike. The guy selling the bikes was a tool and die maker like myself and we hit it off pretty good. He told me the other bike sold to a guy with a black Porsche because the paint matched it. He wanted his workshop manuals and copies of the Norton news to go to someone who would appreciate them. He offered to throw them in with the deal. I left without purchasing it and when I was about a mile away my wife told me I should go back and buy it, which I did. The guy said he knew I would be back.  I went back with money the following day and drove it home which was about 30 miles. I learned a lot about the ills of Norton clutches and worn Amal slides on that short drive home. Below is a picture of my Norton in Rogers City, MI shortly after I purchased it. Future posts will document changes I have made to get it running properly and increase performance. 

Fixing the Norton Clutch

I decided to tackle the slipping clutch first. When it was disassembled I could see it was in pretty bad shape. The clutch center was not one of the hardened ones and it was full of grooves from the clutch plates. The fiber plates were worn out, and upon inspection on a surface plate, I determined the steel plates were warped.  I could also see what appeared to be gear box oil in the clutch plates. To sort all of this out I purchased a hardened clutch center with a new bearing , new steel plates, and new fiber plates. The clutch rod also had significant wear on its end. I replaced this with a new rod made from a hardened pin. I ground o-ring grooves in it to stop the oil from transferring across from the gearbox. I put silicone sealer on the bottom half of the primary case when it was re installed. This seals it from oil leaks but will allow the top to be pulled back for removal.

The new components were assembled and the clutch worked well. It has been together for about 5000 miles with no issues. I have found that filling the primary case with the bike on its side stand allows adequate oil to be added without overfilling it to the point it fouls the clutch. I do this frequently to ensure I have enough oil. It is not often that I add oil. Usually I have to drain it out. It must be engine oil working through from the wet sumping that occurs when it sets for a while.

Stopping Wet Sumping & Blue Smoke

The Commando smoked when it was first started which is problem I have found to be common on them. My first thought was that the valve guides were worn out. I took apart the head and checked the specs on everything. They checked out good. The only issue was the valve guide seals were hard. I replaced them and the smoke cleared a bit but I found another issue, wet sumping.  Nortons are a dry sump design, which means oil is stored in a remote tank and not the engine. When oil drains from the tank into the engine it is called wet sumping. A good indication of this is a significant drop in the oil tank level after the bike sits for several days to a week. When starting my Norton after it has wet sumped it would smoke significantly. It filled my garage with blue smoke to the point I was afraid one of my neighbors would call the fire department. No kidding. I have to admit it was a good way to clear out mosquitoes, although embarrassing when my Harley Davidson owning neighbor would see it happen. Oil would also drip out of the exhaust pipes. I tried several methods to stop this from occurring but none worked. My first attempt was to grind the oil pump back into specs. This did not slow down the oil flow. My second attempt was based on information from another Norton owner. I turned the bike over to its compression stroke when I finished riding. This supposedly blocked crankshaft holes that let oil flow into the engine. This didn’t work either.

My next attempt was to send the timing cover to Alternative Motorcycle Repair to have a check ball installed into it. This worked pretty well. The Commando will still wet sump a little but not as bad is it was without the valve. I no longer get the clouds of blue smoke even when it sits for a couple of weeks. I will have this modification done on my next Norton.

Tuning it to Run Properly

Once the clutch and smoking were sorted out I focused on making it run better. The bike would not idle which I found out could be attributed to worn carburetor slides. The bike had 12,000 miles on it with the original Amals. I purchased new carburetors which took care of the problem. Pickup under acceleration was slow and the points looked to be in need of replacing. I purchased and installed a Boyer electronic ignition to set the timing straight. This made the bike run very well and I will install electronic ignitions on all of my bikes. In 1974 Norton timing chains still had manual adjusters. RMA Engineering makes an automatic adjuster which I purchase and installed. It has about 5000 miles on it with no issues or further adjustments. Everything appears to be working fine but I suppose I won’t know for sure until I take it apart.  

Mechanical Fixes

There were a few odds and ends I wanted to work on to make the Norton perform better. The rear wheel adjusters did not function well. The adjusting screws did not always touch the rear axle when the chain was adjusted properly. I made a new set out of stainless steel to capture the axle and provide a more positive wheel alignment. A photo of these follows. I also made an alignment tool (board) to get both wheels are running the same direction after adjusting the chain. This is easy to do for a Commando since both tires are the same size. All you need is a straight board long enough to cover both wheels and cut it out to clear the center stand.  

The brakes on the Norton were adequate but I thought they should be better. Norton chrome plated their front discs in 1974 which reduced the friction and stopping power. I removed the chrome on a surface grinder improve this situation. I also drilled out the discs. These modifications together made a significant improvement in brake performance. Both are well worth doing. If you cannot do these modifications yourself I would recommend having them done by a professional source.

Fork Springs on the Commando did not work well for my weight, which is about 215 pounds. They were very stiff.  The person I purchased the Norton from was much bigger than me. He may have put in heavier springs from another bike. I installed a set of springs from a 750 Commando and they dove under heavy braking. Next I purchased a set of springs from Progressive Suspension. These dove even worse and bottomed hard at moderate to heavy braking. I ended up cutting off the original stiff Commando and progressive suspension springs until I found a combination that worked well. I have two thirds progressive springs and one third heavy Norton springs. An odd way to come up with a suspension setup but it works for the type of riding I do.

Dzus Fasteners

So what the heck is with the funny fastener that holds the left side panel on? I discovered it was called a Dzus and was used in the aircraft industry and somehow made it way into the Norton parts list. Bummer.  I wasn’t too concerned with this piece until I went on a trip with the Commando and overloaded the tool bin. While coming to a stoplight in a town about 300 miles from home I heard a terrible racked below and to the left side. I looked down in horror as my tools went sliding on past me into the intersection I was stopping at. To maximize the damage the panel fell logo side down removing substantial paint. I put the thing back together and when I returned home I made a positive lock pin to hold everything together. I have had not issues since that fix was put in place, although it is a bit more difficult to use than the standard Dzus.  

Rogers City Road Rash ....

Dzus modified with positive lock clip. 

Installed and locked in place. 

On a side note I was fortunate enough to find a NOS side panel in Pacific Coast Blue at “Flint Indian Sales” before they went under the gavel. Lucky me.  They had a whole box of NOS panels, racks of Amal carbs and many other NOS parts. They were prepping for their auction and had many interesting items on display. My favorite was an early 40’s Indian Chief inline 4 with a sidecar still showing its original “City of Flint” police paint job. It was a real museum and I wish I had money to buy more. The auction was one of the largest ever held for vintage bike parts when it was all finished.  A great overview of it can be found at this link.

Sorting out Electrics

When you talk to people about British motorcycles, Lucas electrics will frequently come up. This is for a good reason. While I think Lucas electrics were most likely always problematic, being 30 to 40 years old certainly exacerbates the problem. The worse issue I experienced was with the large junction block under the fuel tank. This block has many wires running into it which are insulated from one another. When the rubber in this block deteriorates, various circuits short out. It caused an intermittent problem that took me a long time to find. I replaced the block with individual connectors. Problem solved.

Turn signals on the Norton Commando are a great safety feature in theory. My first problem was with a rear signal which vibrated off during a ride. I promptly replaced it and about a month later the bracket that holds it broke. When I arrived home the signal was hanging by the wire. At least I did not lose it. I made a heavier bracket and welded it back together. This held for several years and eventually the bracket broke off again. Once again I welded up the bracket but this time I elected to remove all of the turn signals. Although I like to have them from a safety standpoint, the odd switch lever operation was difficult for me to work consistently. It is different than my Triumph Trophy 1200, which is my primary rider, and I frequently found myself signaling the wrong direction or forgetting to cancel them. This situation was probably more dangerous than using hand signals. So far the PO-PO has not called me on it.

One positive improvement I made in the name of safety was an LED tail light. This was purchased from British Cycle Supply Company. I also bought a reproduction tail light so I did not have to destroy my original one to mount the LED. Installation was simple and I did not experience any issues. I also put one on my BSA Lightning with equally positive results. The amp draw is less for LED’s than the factory bulbs which should help the Lucas system survive. The reproduction tail light lenses did not have the reflector strip in them and were not as bright as the OEM unit. I used the original lenses for this reason. 

LED tail light being installed in my 70 lightning housing. A great upgrade.


One of the problems I have had with my Commando is with the ignition switch. All of the power for the headlight runs through it. Sometimes when you switch on the light you see it arch and the bike will short out. Switching back and forth between lights and no lights usually cures this although I have burned out one switch. To rectify this problem I put an automotive relay into the system for my headlight. The power to the headlight now skips the key switch. The ignition opens the relay switch that sends power to the headlight. The power still goes through the handlebar switches but they have not been an issue for me. There are several good wiring diagrams on line to follow. I have seen overviews of duel relays in the headlight to bypass the handlebar switches as well as the ignition switch, which may be a better solution. My setup works well for me so I will leave it as is for now.

Trouble Shooting the Boyer

Spring through Fall I ride bikes and work on them in the winter. Unfortunately I was forced to work on my bikes a few times this summer to keep them going. OK, so I actually like working on them too. The Norton had issues with the Boyer electronic ignition this year. It has been in the bike for about 25 years so it came to me as no surprise. I went for a ride and was about 100 yards from home when it started backfiring. I turned around and idled home as it did not backfire at idle. After checking for all of the normal fuel problems I researched Boyer issues on the internet. I discovered that the bullet connectors linking the pickup wires to the box are a weak link. Mine were lightly corroded. Since very low amperage comes from the pickups this is a show stopper. I removed the bullets and soldered the wires together fixing the issue. I also found the wires under the points cover were cracked where they come through the case and make a tight bend. I soldered in a longer piece of wire to reduce the tight bend. Good for another 25 years…..

The connectors that took down a Norton. They actually look pretty dodgy.....

Making an Oil Tight Norton

This has been a work in progress for the past 25 years. I had the Norton pretty leak free until my Boyer developed a short which is detailed in the preceding notes. After the backfiring caused by the short an oil leak developed from the front of the cylinder head. I had been fighting this slight leak for years and had finally fixed it with the addition of a Dorman PCV valve. It was considerably worse after the Boyer incident. During the past winter I re-torqued the head to see if it would reseal the tunnel area but it had not. I noticed the head bolts were all significantly below torque specs which meant the threads were probably pulling. Norton head bolts should not be used more than 3 times for this reason according to some experts. I thought I would try the “re-torque” in the spring and check the results. It turned out that there were none. On to the next attempt……….

The leak came from between the fins on the front of the head and appeared to be centered on the right push-rod tunnel. I did not know this when I took it apart and thought it was a head gasket problem.

I pulled the head, replaced the hardware, and installed a new copper ring gasket from Norvil in the UK. I discovered the Dorman valve, which had about 500 miles on it, was no longer working. The head oil lines were the original ones and brittle from age. I replaced these with nylon hydraulic line purchased from a local supply. They were a bit tricky to install as heating them up with a gun had to be just right. Too much heat and they folded over, not enough heat and they would not go on the fitting. Purchase more than you need if you attempt this. After all of this I started the bike up and it ran fine although after it warmed up it leaked as bad as it did before pulling the head. I was not sure where to go next. Although I thought the failed Dorman valve might be part of the problem, I thought bigger solutions may be needed. On to the internet…..

An improved PCV from Yamaha…. You will find it at:

After doing research on the internet I found that the Dorman valves do not last long and a better fix is a breather from an XS 650 Yamaha. This is a reed valve design that lasts longer and offers a more positive seal.  I purchased one from Mike’s XS parts (#15-6077) as a last ditch effort to fix this leak. To my surprise the oil leak from the front of the head stopped and I am back to normal oil leaking status. Although I thought this was a “hail Mary” it actually worked!

Oil leak fixed and time to ride!. 

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